J-Rod

Ok, I am going to copy in the portions of the previously locked thread that mattered, and leave the TR portion out so that hopefully this time it won't get locked... So, I'd like to get back to the topic of cams. I'd like to leave any talk about TR or TR cloning a Comp lobe, or any of that talk aside. I'd like to keep the topic of this along the lines of ideal camshaft design, calculating VE, etc...

So, here is everything from the last thread with the TR stuff edited out...

https://ls1tech.com/threads/showflat...t=all&vc=1


93 Pony. Can you post the math on one of your good cam designs showing us the VE calculations, and how you derive that one cam is better than another, or how to optimize the cam profile. Also can you illustate what designs you would feel would be better than another.

I am interested in your claims, and would like to see the data you are using to arrive at your conclusions, along with the math to support them.

Here is the Comp spec sheet for XE and XE-R if you'd like to use it as a reference. Thanks.



93Pony-
J-Rod,
Sorry...I no longer post all that valuable info.
Do some searches on past threads I've posted in here & on Norcal-LS1 for some good info. Too many I have given great tech too....only to be burned by them ordering cams with my specs from another company. My knowledge of camshafts is highly sought after..by not only the average Joe. Giving it away in posts does not make buisness sense...

I give my knowledge to those who order cams from me. Answers to all the questions they could possibly ask. What they walk away with is a cam with no comprimisses...& in return they take my cam to the track & prove my theories once again.




93 Pony. I registed on Norcal-ls1 and read the majority of your posts. I really didn't find any specific information about how you are making the determinations. I am interested in hearing how you are coming up with your lift numbers when comparing XE to XE-R lobes. I did see one post where you made a few recommendations about 3 specific grinds using XE-R lobes.

Just a couple of quotes from you:

http://www.norcal-ls1.com/forum/show...threadid=17085

For instance:
218/218 112LSA has -6 degrees of overlap & should pass smog with no problem....on a good tune of course!

The TR 224/224 114LSA has -4 degrees of overlap....yes, more overlap & will be harder to smog. But it too should still pass on a good tune.

Too bad TR doesn't have a 220/218 109, 110, & 111 LSA's. They'd work great with stock heads. The 109 pulling the hardest up top (almost as much as the TR 224/224 112LSA) & the 111 being the easiest to smog. All with excellent low-mid range power.

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Dot-to-dot....this cam has 4 degrees of advance built in right?

Intake to exhaust ratio is ~70-75% before the exhaust is bolted on....& the intake will definately restrict the heads. So, figure about 80% ratio is what you'll end up with.

The single patter TR 224 will work quite well, but I'd retard it to a 116ICL for these valve events:

Intake opens @ 4 ATDC
Closes @ 48 ABDC
Exhaust opens @ 40 BBDC
Closes @ 4 ATDC

If you wanted something more 'wild' I could do some research. I think a few more degrees of overlap would give a nice boost up top.
Too bad TR doesn't make that 227/224 on a 111 or 112LSA. That'd really work well w/your motor. Hmm....I could probably find the lobes they use (or better) & get back to you.
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The small reverse TR 227/224 will work just as good as the 224/224 w/a 150 shot. w/a 200, the single pattern would probably work just a little better. But, the 227/224 will make more power on the motor then the 224/224. & likewise with the 150 shot. On the 200, the 227/224 will still make more power, but the power gap between the 2 cams would be closer.

High compression (11 to 1) would benifit both cams.

I believe the TR 227/224 would work quite well on a 111LSA. If you want even MORE umph, then tighten it up to a 109!

The 111 will have 3.5 degrees of overlap @ .050 lift. (not much really) The 109 will have 7.5 degrees. If installed correctly (so the valve overlap is directly over TDC & slightly biased to ATDC) idle should not be too much of a concern.

---
Here are a few LS1 cams I've speced out from Comp's lobes.
Comp charges $400 for a custom LS1 cam BTW.

Small smog grind:
212/210 109LSA .571/.566 w/1.7's. Deceptively small lobes that will make significantly more power then the stock cam. -7 (negative) degrees of valve overlap @ .050 for easy smogging.

Large smog grind: (For spdfreakls1)
218/218 111LSA .578/.553 w/1.7's. Small reverse grind @ .200 lift. Great for N/A or N2O. Fast ramp-rates. -4 degrees of valve overlap @ .050 that should pass smog without problems. LSA can be tightened up to a 109 for those that don't require smog. Great for stock heads.

Ported heads grind: (For GR8WHITE)
226/224 111LSA .590/.561 w/1.7's. Reverse grind ment for N/A applications & small nitrous shots (150). Definately gonna go fast with this puppy! Duration @ .200 lift (were heads really flow) is easily 40 degrees more then stock! A little large for stock heads. 3 degrees of valve overlap @ .050 lift for high rpm power. LSA can be tightened to a 109 for even more upper RPM power.


I can make just about any cam for any application.
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No smog worries right....

Go with the 218/218 109LSA. Performance is nearly the same as the TR224/224 112LSA, but with better valve-events so low-midrange power will be substantially higher. Upper rpm power will be nearly identical.

The TR 224 lobes have 145 degrees of duration @ .200 lift. The 218 intake lobe I chose has 142. Set on a 109 will give identical valve overlap as the TR224 (so peak power will be at nearly the same RPM) but with faster ramp-rates which will help idle & low-midrange throttle response. The reverse split will also help low-midrange power.

You'll need a free-flowing exhaust. Longtubes, etc. With that, you're car will probably be the fastest stock headed N/A LS1 around. Couldn't really tell you the power gains will be. I have no idea what the stock LS1 cam looks like.

BTW, the 224 lobe I used on that hotter cam is identical to the TR 224 lobe. The 226 lobe I chose is just a bit larger then the TR 227. (9 degrees larger!) Actually the TR 227/224 is not a real reverse split. The intake lobe is significantly softer then the exhaust. Duration at .200 lift looks like this 141/145.


http://www.norcal-ls1.com/forum/show...threadid=16928


Turbos are limited in exhaust duration. Let me clarify... For a STREET driven turbo car where low-end is important, the exhaust lobe is limited.

Because of the pressure in the exhaust manifold, turbo motors have a longer 'power stroke' then N/A, SC, & Nitrous cars. These motor's power stroke is from 0 to 90 degrees. Turbo motors continue to push for another 45 degrees of crank rotation. Hard one to follow, but true.

Stock cams work so well with turbos becuase of the lack of overlap & small lobes. Aftermarket cams are setup for N/A & SC's for the most part & open the exhaust inside the power stroke of a turbo motor. Average spot to open the exhaust valve is ~45 degrees BBDC @ .050 lift, which is ~ 70-80 BBDC @ .006 lift (depending on ramp-rate). So, the exhaust lobe on a turbo motor *should* be opened late to avoid bleeding off power. At roughly 60 degrees BBDC is were you can open the exhaust valve. Add this to the lack of overlap on a turbo motor, because exhaust manifold pressure is ALWAYS higher then the incoming intake charge (by 1.5-2 times depending on compressor efficiency) & you can see why large cams don't work so well with these motors.
So, if you're following me, a street turbo motor is limited to ~ 260-270 total duration on the exhaust side. & that's WITH ~40 degrees of overlap @ .006. (nominal stock overlap)

Track turbo motors use more traditional N/A grinds as they stay in the upper RPM band were overlap will actually help the turbo make power. But it KILLS the low-end.

Turbos make full boost by ~3000rpm & therefore make tons of torque, so most don't notice that the N/A cam they're using is bleeding off power.

I'm going for the most efficient combo as possible.... This new cam will open the exhaust @ 60.5 degrees BBDC. As opose to 69 BBDC w/the stock cam in there now.

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The tech guys at Comp think I'm crazy. I orded this cam with 6 degrees of retard ground in!

http://www.norcal-ls1.com/forum/show...threadid=18958

I see you are learning Grasshopper.

Try this one on for size:

Intake 3727
Exhaust 3725
113LSA
113ICL (straight up)

Or

Intake 3727
Exhaust 3726
114LSA
114ICL (straight up)

Or

Intake 3727
Exhaust 3726
113LSA
114ICL


Thanks for the lobes! I now have them saved for sure! (I hope)

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Most of Comps lobes are on their website.
http://www.compcams.com/catalog/
pages 226-248
The good Hydraulic roller lobes are on pages 229-231. Mind you, these are not all the lobes Comp offeres.....the list is outdated & they have many more lobes. But this is a good list.
Also one thing to note. You have to convert lobes when they're put on larger/smaller cam cores.
SBC has the smallest cam core, followed by BBC, Ford, & the largest is the LS1. These lobes will grow & shrink depending on what they were made for & what core they're put on.
For instance, SBC lobes grow ~4 degrees at .006 & .050 when put on a Ford core. The same lobe will grow ~6 degrees when put on an LS1 core.

Something else that I didn't really claify.....those XE-R lobes are very nice. They are more aggressive then the majority of the XE lobes, but there are a few XE lobes that are more aggressive then the XE-R lobes. As peak lift goes up, the lobe gets more aggressive. So, the XE lobes that measure .600 & up are more aggressive then the XE-R lobes. It's not a lot, but it is significant when you're extracting every last bit of power out of the combo.

For instance. The 224 lobe (lobe # 3313) when corrected for the LS1 cam core measures 276 @.006, 224 @.050, & ~141-142 at .200.
A comparable XE-R lobe is the 3715, yet a more agressive XE-R lobe is the 3722. Same .050 duration as the other 2 lobes, but measures 4 degrees larger at .200. Also notice lift increased. The higher the lift for a given lobe, the more .200 duration it has.

Another comparison is Comp lobe # 3634, when converted for the LS1 core measures 284/234/155-156 (closer to 155.5 @.200).
A comparable XE-R lobe is the 3727 which measures 283/234/155. these lobes are VERY close in performance....as is peak lift. In this case the Ford lobe being slightly more aggressive.

Compare some of these lobes & you'll see what I'm talking about.


You have piqued my interest with your discussion of VE which I am going to assume you mean valve events rather than Volumetic Efficency.



Ok, so using the recommendations you made off the XE-R line of lobes

Intake 3727
Exhaust 3725
113LSA
113ICL (straight up)

So, you end up with a 234/230 .598/.592 113 0

Or

Intake 3727
Exhaust 3726
114LSA
114ICL (straight up)

234/232 .598/.595 114 0

Or

Intake 3727
Exhaust 3726
113LSA
114ICL

234/232 .598/.595 113 -1

Ok, now this is my understanding of things. There are four timing parameters that define how your engine will operate. These are intake valve opening (IVO), intake valve closing (IVC), exhaust valve opening (EVO) and exhaust valve closing (EVC). It is relatively easy to derive these parameters from the specs supplied by camshaft vendors (lobe center angle (LCA), intake centerline (IC), intake duration (ID), and exhaust duration (ED)) assuming all these parameters are specified.
IVO = ID/2 – IC
IVC = ID – IVO – 180
EVO = ED – EVC – 180
EVC = ED/2 – 2*LCA – IC

To really appreciate how an engine works, and how to get the most performance, we must talk about wave dynamics. But I should warn you that even this discussion is a simplified view of engine operation. As gases move in and out of an engine, they are constantly compressed and expanded, heated and cooled, with laminar and turbulent flow. Each valve edge, bend in a pipe, gasket, fitting, thermal change, etc. has an affect on how these gases flow and will affect the behavior of the engine. Even complex computer simulations cannot fully predict engine behavior, but they can come pretty close. When valves open in an internal combustion engine, gases don’t just flow smoothly into or out of the cylinder. There is usually a significant pressure differential between the two sides of the valve when it opens. This causes a sudden acceleration of gas molecules that form a pressure wave. This is similar to an acoustic wave caused by clapping your hands, but the pressure waves have thousands of times higher pressure differentials.
But the pressure waves still behave in much the same way as acoustic waves. Pressure waves can be positive compression waves, or negative expansion waves (sometimes called rarefaction waves). The behavior of these pressure waves in a pipe is very important to understanding engine performance.
When a pressure wave traveling down a pipe encounters a closed end (such as a closed valve), it will be reflected back in its original form (i.e., a compression wave is reflected back as a compression wave). But when a pressure wave encounters an open end (such as open headers), it is reflected back “out of phase”, so the reflected compression wave becomes an expansion wave. These reflected waves can be used to great value in optimizing engine performance.
Valve timing events are referenced to TDC (top dead center – the piston is at the top of its travel) and BDC (bottom dead center – piston at the bottom). If a valve event is specified as 20 degrees ATDC, this means that it occurs when the crankshaft has rotated 20 degrees past (after) when the piston was at TDC. Likewise BBDC means crankshaft degrees before bottom dead center.
In a simple engine model, we’d expect the exhaust valve to open at the end of the POWER stroke when the crank was at BDC. The piston would then force the exhaust our of the cylinder during the EXHAUST stroke. It turns out that this valve timing is very inefficient. By the time the crank has reached 25 to 30 degrees past TDC during the POWER stroke, almost all the power has been transferred to the crank. By opening the exhaust valve (EVO) during the middle of the POWER stroke, we can take advantage of the residual pressure in the cylinder to start to blow the exhaust our instead of forcing the piston to pump the exhaust out. Of course, there’s a delicate balance between the power wasted by opening the valve too early and the power wasted by forcing the engine to pump out the exhaust.
But there’s an added benefit of early EVO. The high pressure in the cylinder when the valve opens will cause a strong compression wave to be generated out the exhaust port. This compression wave will reach the end of the headers and reflect back as an expansion wave. If this expansion wave reaches the cylinder before the exhaust valve closes, and can further assist in removing the last remnants of exhaust from the cylinder and even assist in starting with the intake of fresh fuel/air mixture as we’ll discuss below.
A mild street cam generally sets EVO at 65 to 66 degrees BBDC, while an aggressive racing cam might set EVO as much as 85 degrees BBDC (although keep in mind that this is when the valve just starts to open, not when significant flow can occur).
The next valve timing event to occur is the intake valve opening (IVO). Note that this occurs before the exhaust valve is closed. IVO is the least sensitive of the valve timing events, but an earlier valve opening can benefit from a broad expansion wave from the exhaust system to help accelerate the air/fuel mixture. If an expansion wave is not present, early IVO timing will allow exhaust gases to flow into the induction system since the cylinder pressure will almost certainly be higher than the intake pressure. This is called reversion and will have a damaging effect on performance by contaminating the fresh fuel/air mixture and heating it up (making it less dense).
A typical mild street cam will open the intake valve around 10-12 degrees BTDC. The IVO for an aggressive race cam will be as early as 50 degrees BTDC. For a high performance street engine, the benefits of going beyond 20-25 degrees BTDC do not seem to outweigh the risks of reversion at lower RPM.
The next valve timing event is EVC, exhaust valve closing. This determines the end of the overlap period (when both valves are open) and, of course, the end of the exhaust cycle. If a strong scavenging wave from the exhaust system is present, a later EVC can provide significant help in drawing in the gasses from the intake. With properly tuned headers, the scavenging expansion wave will be at its peak at the RPM that delivers maximum power, further increasing power. But at lower RPMs, this expansion wave will arrive early and will be followed by a positive compression wave. If this compression wave arrives before EVC, reversion will result, significantly affecting performance. This is why “hot” cams that are designed to maximize high RPM horsepower have such poor idle characteristics.
Exhaust valve closing typically occurs around 10 degrees ATDC with a mild street cam and can occur as late as 50 degrees ATDC on a hot race cam. Typical high performance street engines will have EVC at around 30 degrees ATDC.
The final valve timing event is the intake valve closing. This is probably the most important valve event and the most sensitive to the induction system used on the engine. The more fuel/air mixture that can be forced into the cylinder, the higher the performance will be. So IVC is normally delayed until well into the COMPRESSION stroke. But if IVC is delayed too far, the building pressure in the cylinder due to the piston upswing will exceed the induction systems ability (through pressure waves and gas molecule momentum) to hold back the pressure and fuel/air will flow back out of the cylinder.
As with the exhaust, a pressure wave will be generated in the intake as well. In this case, an expansion wave is generated although will less amplitude than the exhaust pressure wave. The strength of this wave will be determined by the amount of suction that can be created in the cylinder resulting from the piston downswing and the exhaust scavenging wave.
When the expansion wave reaches the end of the intake runners (or the top of the air horns in they EFI system we’re using), it is reflected back as a compression wave. By the time this wave reaches the cylinder, the intake valve is closed and the wave bounces back out. This wave continues to oscillate in the intake system until the next time the intake valve opens. Since the length of the intake runners are typically significantly shorter than the exhaust headers, the frequency of the pressure wave is considerably higher – usually two to three times higher – so by the time IVO occurs, the wave has bounced back and forth several times.
As with headers, the intake system must be tuned for a particular RPM to deliver the most benefit from this pressure wave oscillation. The air horns on some induction systems (Webers, TWM, Kinsler) are designed to spread the reflection wave so that it will provide benefit over a broader RPM range.
Intake Valve Closing is typically set at around 60 degrees after BDC on a mild street came, and as much as 85 degrees ABDC (almost to TDC) on a very hot race cam. An engine with this kind of hot cam will have a very narrow power peak and be designed to run at very high RPMs. For a high performance street engine with a well tuned induction system, IVC should be 65 to 70 degrees ABDC.


Just wondering if you agree or disagree with this? If you have any specific information that you'd like to share in terms of your personal views on ways to determine those optimal valve events.

Also, here are two cams from the "strongest" LSx packages out there. The Cartek IIx package, and the LGM G5X2.

Cartek
224/228 .581 .588 +2(not sure) on a 113 LCA installed at 113 icl
G5X2
G5X2:232/240 595/609 112

Both are making around 450+. The best I have seen are around 475RWHP. Using your calculations would you expect to make the same power, all things being equal with a camshaft of your design. If so, what would you do....

93 Pony
You have a solid grasp on what's going on in the 4-stroke internal combustion engine.
I tend to approch things a little differently with these EFI intake restricted motors. Due to runner length & the current lack of cost effective shorter runner intakes, the LS1 is limited to a 4800rpm torque peak....& thus 6200-6400rpm HP peak (due to the wave of the incoming intake aircharge as it bonces between the closed intake valve & open air plenum). When I do a cam for a setup like this, I go for max cylinder pressure under 6200rpm.
The area most cam companies error on is the exhaust. This causes problems with these limited intake designs. The exhaust VE's are the most important on these setups.
Simply put, on an N/A motor the intake aircharge is not assisted. (leaving wave dynamics of the aircharge out for a moment).
After the combustion stroke there is tremendous pressure in the cylinder. As soon as the exhaust valve cracks open it flows a LOT of air. It's basically boosted out of the cylinder if you want to look at it like this. Having the exhaust valve open too early not only costs heat (power) & velocity through the exhaust runners, it also empties the cylinder before the intake valve is open enough to take advantage of the pressure differential. (in a limited overlap/smogable camshaft this is especially true) This causes exhaust reversion & is one of the key factors in surging problems. By the airflow reversing course it is loosing a lot of it's inertia. Typically this is overcome before peak torque however. So only low-speed issues are present. At the track these motors are always above 4500rpm so this does not affect track times too much. Stilll....there is significant power lost by allowing reversion. So it makes sense to open the exhaust valve a little later & increase the overlap a bit. By adding advance into the camshaft this makes the problem even worse as now you're opening the exhaust a few more degrees earlier.....& shortening the effectiveness of the intake unless you have significant overlap flow to over come this.
Simply put, advancing a cam makes it more exhaust bias relative to TDC. Retarding a cam makes it more intake bias relative to TDC.

For those 2 cams listed the only thing I would do to increase power would be to reverse the lobes. Intake for exhaust.

Instead of typing more I'll just leave a link to some more good cam info.
http://www.wighat.com/fcr3/


J-Rod

Thanks for the link. Now, you said that what you would do would be to simply reverse the lobes. So, on a G5X2 for example, you'd change the cam from 232/240 .595/.609 112 to 240/232 .595/.609 112. Ok, since you explained why you feel that EVO is important (and it is), would you in fact leave the cam specs this way. Would you advance or retard the camshaft or the exhaust events? You really seemed to have spent a lot of time thinking about some of your smaller cams. I am wondering if you have given any consideration to larger profiles...

As an example several car equipped with a G5X2 and ported LS6 heads make between 450 and 470 RWHP. A car equipped with one of the new TR 236/230 .597/.582 cams made 426hp/392tq. Now there are a lot of variable like one was in a Corvette, and one was in an F-Body. Also the rear gears affect things. KH24's Cartek Vette is the cartek car that comes to mind, as his car dyno'd 472RWHP with the Cartek X pkg.

I understand your philosophy about surging and low speed drivability. And in fact on the small smogger cams you appear to to have made some good numbers. Ok, take yourself away from the smogger cams and look at folks who want to make good power. To do so in a strictly NA application you will need a lumpy cam, and your bottom end will get a bit soggy. Its the nature of the beast. Using the methods you have described, can you design a cam that will make as much power as some of the cam packages I have specified, or do those simply stop being quite so critical when the cam get larger...

Also, on the manifold side, there is a quick and easy way to get a short runner intake with a nice fat plenum on it. You take an ls1/ls6 intake turn it over and cut the floor out of it. Then you remove the length out of the "ram tubes" you wish. As a side note, doing so drops performance across the board. Also, except for big stroker motors short runner manifolds at this point have really killed bottom end on LS series motors. No one to date has made "good" power down low with them.


93 Pony -
J-Rod,
For those 2 cams I'd reverse the lobes & keep the LSA/ICL the same.
Yes, I do have larger profiles available...with just as much thought put into them. As of yet, nobody has wanted one.

Basically I can make a cam that makes the same power as a larger cam, but idles/drives much better. Simply making a more efficeint combination.
Peak power with the larger cams won't differ much with one of mine. What will differ is AVG power & drivability. When you look at the larger exhaust bias profiles they have so much overlap that they don't get nearly as much reversion as the smaller exhaust bias cams. These larger profiles with lots of overlap will actually jump-start the incoming air-charge. But....the way I see it, the intake lobe determines how much airflow you can squeeze into the cylinder. A larger intake lobe will make more power up top. With an exhaust bias cam what this means is a MUCH larger profile due to the exhaust lobe being that much larger. With a reverse-split you can use the same big intake lobe with a much smaller exhaust lobe...add in the same amount of overlap & the reverse-split will make just as much power as the standard, but idle/drive nicer. Of course this is assuming both cam profiles have good VE's.

That's the first I've heard of being able to modify the runner length of the LS1/LS6 intake. Interesting.... I do know of an 11 inch runner plastic intake that will be available soon after the AFR's come out. It'll probably be a stip-only intake....I wonder how it'll respond.

472RW is DAMN impressive! Can't wait to see what the new AFR heads & shorter intake will do in a combo like that.


J-Rod

There are actually 3 intakes in the works right now. Futral is one the Wilson/FAST manifold is the other, and there is talk of another intake (I forgot off the top of my head who it was). The Wilson/FAST manifold look promising. Right now there are several aluminum short manifolds out there. But as I said, they don't seem to gain on the 346s, only on big motors.

Now, in dyno tests with standard splits vs reverse splits. Namely a G5X2 vs a BIG reverse split. The reverse split made better power down low (0-3900) at 3900 the HP and Torque peaks crossed. The G5X2 made more power all the way from 3900-7000. It also made more peak torque (almost 20 lb ft) right after the two came together @ 3900. But the Reverse split made 30 lb ft more torque @ 3200 and 20 more HP.

Again, I recognize that in many applications the reverse splits make drivability better. They make tuning easier. They in fact may make more HP and torque in some applications. I just as yet have not seen a reverse split amke the smae power as any of the standard split cams.

As for the new manifolds, I expect a lot to be done when those hit the market. It will be interesting to see which manifolds respond best to the addition of the mainifold.

My reason for asking about the big cams is really quite simple. You spent a lot of time explaining why you felt your 220 cam was superior than the similar TR grinds, and why you designed it the way you did. Most of the cams I have seen you site are smogger cams for you local Cali folks.

Are there any cams larger than the ones I have seen you post about on Norcal-ls1 or here that you have postable results of? As in actually in car dynos especially a dyno of before with brand X cam vs yours, or from stock vs yours. I just wanted to see the gains you are making.

Also, you made mention of one of the TR grinds that you felt was better than most since it was closer to what you felt were more ideal design specs. Can you share which grind that is, and why you feel it is superior in design.


Her eis another cam for you to critique.
This cam is an enlarged version of the MTI X1 cam.. reverse split with larger specs...

Competition Cams
Intake : lobe #3660 : .596 lift, 252 duration
Exhaust : lobe #3655 : .596 lift, 244 duration
Intake Centerline : 114
Lobe Separation : 114

If you'd like how about some suggetions on what you feel is the ideal max power cam on say a vehicle with bolt ons and ported ls6 heads. Do you think you can make 450-470RWHP?


93Pony -
J-Rod,
As of yet, no one has one of my larger grinds...so there is no hard data on them yet. I have seen excellent results from local large reverse-spit cams. Of course, these are fords....but the tech for them came from an LS1 guru. One car has a 232/228 110LSA & is running harder then ANY other stock shortblock 302 around....in a heavy convertable with smaller heads then the competition. The local cammed & bolt-on LS1's have yet to beat him. It took TEA 6.0 heads & a hefty cam to pull him. The other car is a 347 with a 244/236 108LSA cam & has run low 11's at 124mph at 3300lbs. There has not been an LS1 around here yet that can keep up....even on the juice.
You may think this has nothing to do with LS1 cam tech....but the theories are the same...as are the results we've seen....although the LS1 seems to respond much better to these type of cams. The main reason none around here have gone with big 'ol cams is piston to valve clearance. No one wants to pull their motor to notch the pistons....yet. I'm sure in due time one or 2 around here will do it & slap in a really healthy cam. We have the piston cutting tools....all we need is someone that wants it done.

SStroker Ace
Is this a joke? Comp has everything from manual cam grinders for Winston Cup cams (the manual ones with a good operator are better than the high tech CNC ones) They also have countless CNC cam grinders for the stuff we all run.

I would really like to know who grinds TR's cams. I really wonder how many people here understand the complex physics that go into cam lobe design. We are not just talking about velocity & accelleration but the ^3,^4,^5 powers of veliocity. That along with surface finish and the minor bumps and waves in the lobe surface, all mean alot. There is a good reason that about the whole Winston Cup field runs Comps stuff. Roush a couple years ago started doing cams in house, that was about the time between when Mark Martin was finishing second in championships to about 1-2 years ago when they had guys like Jeff Burton, Kurt Busch and Matt Kenseth started doing well. If the cam design doesn't mean much then how come Roush with alot more money behind him than all the sponsors on this board can't make a better cam than Comp?

As J-Rod said, the R&D Comp has with stuff like the spintron makes me wonder if small shops can even compete with that. The OMC that TR has is basically using a lobe very similar to a SBC Comp lobe, in fact you can buy a cam from Comp that is VERY similar as a custom grind. I know I've run the intake lobe on motors before. Hell if you wanted you could get a 224/224 .638/.638 Cam from Comp, which is going to be WAY more aggressive than any of the other 224 duration cams out there. If you wanted you could do a 230/236 .661/.663 cam from Comp, the valvetrain would be a bitch to do but it could be done.

Bret

SStroker Ace
As for J-Rod and 93Pony, they are having a VERY good discussion here on cams, one I wish I got into on the ground floor but the posts are a little long now. If he did or didn't bash Thunder is really irrelatvant now, because the guy knows what he's talking about. Might not have been the best way of going about it the way he did.

The real thing to look at here in this post is that the lobe design really should be left to the rocket scientists. Or Nuclear Physisits as in Comps case. The cam design is another thing. With good lobes a good engine builder/designer can come up with a awesome camshaft for a motor. I know that's how I work, and it looks like 93Pony is on the same page. Now the counter bash saying that he doesn't have VE tables, dyno results etc can sometimes be VERY misleading. True those tools help, but they need to be used right. If you know who Gail Pauly is then you really need to throw those sterotypes out the door. The guy works out of his garage, and designs probably the best cylinder heads for NASCAR reguardless of brand out there. He has machine shops and CNC shops replicate his ports for him and the only hand work he does is on intake manifolds. Not bad for a guy with a shop in his garage. You guys might have the dyno and the facilities, but that still means you need a really good brain to make them all work.

93Pony,

Quote:
--------------------------------------------------------------------------------


"Sorry...I no longer post all that valuable info.
Do some searches on past threads I've posted in here & on Norcal-LS1 for some good info. Too many I have given great tech too....only to be burned by them ordering cams with my specs from another company. My knowledge of camshafts is highly sought after..by not only the average Joe. Giving it away in posts does not make buisness sense...

I give my knowledge to those who order cams from me. Answers to all the questions they could possibly ask. What they walk away with is a cam with no comprimisses...& in return they take my cam to the track & prove my theories once again."


--------------------------------------------------------------------------------



I have to agree with all of that. When I spec out a cam for someone and all it does is end up on the net, or they go someplace else and buy it, that boils your blood. The worst thing is that I'm always scared that they will run the wrong parts with it and break something.

As for the intake design, longer runners on a LS1 might work but I would imagine that it would need ALOT of tapper angle to work well. The 8" setup now is long, but it's one reason that a heads/cam LS1 can out TQ a 383 LT1 by a mile. Acutally the LS6 intake is a VERY good intake design, it was just never meant to be mated to a 330+cfm head.

Good post guys, if we could keep the B.S. it would be even better.

Bret

93Pony -
J-Rod,
If you want to know the TR cam that I think is their best, e-mail me. I don't feel it neccessary to give this info to....everybody....
My honest impression of the enlarged X1 cam is that it's too large in some area's & too small in others. I do not see those lobes listed in the Compcams catalog...so I can't say for sure how they'll work. But in general I'd tighten up the LSA quite a bit & plot better valve events...which would mean smaller lobes.

I do think 450-470RW is possible with the mods you listed & a cam....but I believe that piston notching would be required for a cam with as much overlap as that would require. Since the LS6 intake has a torque peak of ~4800rpm max you'd need significant overlap to get torque up to the 430RW required to produce the HP you're talking about. Basically making all that power below 6400RPM.


SStroker Ace -
Pony,

If you guys want to see a interesting article on Cams go pick up the new Racecar Engineering in Barnes and Noble.

Bret




93 Pony -

93PONY

Sorry J-Rod,
I no longer post all my cam theories. Too many times have I been burned. I stick to proving my theories these days....not talking about them so much.

Reboot

iTrader: (5)

J-Rod, Just for ***** and giggles I had 93Pony order me a cam earlier this week. I hope to have it installed in the next 2 weeks, if Comp can get it ground and shipped.

Currently, I'm running a MTI C1 222/222 .566/.566 112 LSA cam and make around 418 RWHP to the wheels. My current cam stalls and flat lines from 6000-6500.

I ordered a 224/222 .581/.566 113 LSA, which should, by itself, gain about 5 RWHP over my current cam with the extra duration and lift. I let 93Pony determine the ICL and VE's to make the best power for my setup, based on his theories. Once istalled, I will overlay the dyno's and post them up for all too see. This should show whether his Valve Events actually make power in a LS1. If he's right, I should be over 430 RWHP once properly tuned. If not, I will swap to something else (maybe a TR224).

I'll keep you guys informed...

J-Rod

Reboot, I look forward to hearing your results.

93Pony - In looking over one of your old posts, you cited that you had consulted with several tuners to come up with the theories you employ now. You listed Brian Ebert at www.hitechmotorsport.com as one. I am going to assume you probably also spoke with Dema Elgin @ Elgin cams www.elgincams.com. Who else's work do you tend to follow, or do you feel really has a good understanding of camshaft theory?

In looking over one of you posts on norcal-ls1

http://www.norcal-ls1.com/forum/show...threadid=22468


Crash
Club Member

Registered: Apr 2002
Location: Manteca
Posts: Censored
93 Pony... Info needed inside...
Can I get the valve events, ur .02c on this cam

CompCam XE Lobes

3716 / 3719

226/232 .570/.575 112lsa +4


and so you know too I am not tossing the cam I have now



Report this post to a moderator | IP: Logged

07-02-2003 12:34 AM



93PONY
Active User

Registered: Apr 2002
Location: Fair Oaks, CA
Posts: Censored

Not a bad cam. It uses XE-high lift lobes.
Here's a comparison to the cam you have now:

Intake lobe:
Your cam is 2 degrees larger at .006.
" "6 degrees larger at .050.
" "10 degrees larger at .200.

Exhaust lobe:
Your cam is 6 degrees smaller at .006.
" " 2 degrees smaller at .050.
" " 3 degrees larger at .200.

Your cam has 3 degrees of valve overlap at .050, that cam has 5.

Valve events comparison:
Your cam:
IVO: 2 BTDC
IVC: 50 ABDC
EVO: 49 BBDC
EVC: 1 ATDC

That cam:
IVO: 5 BTDC
IVC: 41 ABDC
EVO: 52 BBDC
EVC: 0 (TDC)

You'll be going from a cam that is basically 1 degree intake bias to a cam that is 11 degrees exhaust bias relative to the piston at TDC. Now, this isn't bad as it has some overlap & the intake will be open enough during the overlap cycle to cut down on the exhaust reversion.

If you're looking for more power, this is not the cam for you...it will not make near the power your current cam is capable of. The 10 degrees less intake duration at .200 is gonna take quite a bit of power away. + the exhaust is acutally smaller by 3 degrees at .200 too....so overall the cam will flow significantly less & not have near as steady an idle as you have now.

Been thinking about your setup lately.... Have you checked out the tranny? I know that sitting on the transbrake at the light will heat up tranny fluid 100F degrees for every second you hold it. Sitting at the light like this too long will damage the tranny... A simple check of the dipstick & sniff of the fluid will tell you if it's burned or not. Other then that, you may want to look into another stall. A higher powerband would require a higher stall. I know on turbo applications it becomes extreemely important to match the stall with to the motor. 1 second or more in the 1/4 can be lost by too tight or loose a stall....MPH too. Just a thought...I know very little about auto's & the stalls required for a particular application.
------------------------------

Here is a paper from Elgin on his cam theories:

Considerable information has been recorded about numerous aspects of the four stroke internal combustion engine. Nevertheless, only a small percentage of people really understand how it works and even fewer still know how to modify an engine to suit their needs. I will try to simplify this complex subject by discussing some basic principles that may be overlooked or misunderstood by the average person. First, it is very important to understand the relationship between piston travel directions and valve timing events. The reason this relationship is important is because it is one of the few things that is relatively easy to adjust/change. The camshaft which opens and closes the valves makes ONE complete revolution (360 degrees) while the crankshaft moving the piston up and down the cylinder rotates TWICE (720 degrees). Camshaft timing is usually expressed in terms of crankshaft degrees relative to the piston location in the cylinder. That is, relative to Top Dead Center (TDC) and Bottom Dead Center (BDC), respectively. Note that during the four strokes of a piston in an internal combustion engine the crankshaft will rotate 720 degrees and the piston will be at each TDC and BDC twice.

THE FIRST STROKE.

Starting at TDC, the piston starts from zero velocity and moves down the cylinder during the intake stroke; first picking up speed and then slowing down again when it reaches the bottom of the stroke. As the piston moves down the cylinder, the intake valve is opening. Some air/gas mixture starts to flow into the cylinder as the valve opens, but the greatest gulp comes when the pressure differential is the greatest. This occurs when the piston reaches its maximum velocity somewhere between 70 to 80 degrees ATDC. What governs piston velocity is the stroke, rod length, RPM, and piston pin off-set. The maximum piston speed of the engine is then limited by the resistance to gas flow of the engine and/or the stresses due to the inertia of the moving parts. You must be wondering why I'm talking about piston velocity during the first stroke.

FACT ONE: Volumetric efficiency is directly related to piston velocity!

Volumetric efficiency is a measure of the effectiveness of an engine's intake system and there are about 200 miles of air above the engine just waiting to fill the cylinder with 14.7 psi at sea level. The intake valve is almost closed as the piston reaches BDC, but it does not close completely until after BDC, when the piston is on its way back up the cylinder. The reason for this is because the incoming air/fuel mixture still has momentum even though the piston has slowed way down. We are now starting,

THE SECOND STROKE.

The piston compresses the air/fuel mixture to a high enough pressure and temperature to permit spark plug ignition. We hope that this results in a CONTROLLED BURN, rather than an explosion (detonation), that produces POWER and moves the piston down for,

THE THIRD STROKE.

Power is produced while the gases in the cylinder expand and cool. In most instances, the gases are at a relatively low pressure by the time the crankshaft reaches 90 degrees After Top Dead Center (ATDC), so we can safely open the exhaust valve Before Bottom Dead Center (BBDC) to take advantage of blow- down. Otherwise, the piston would have to push ALL the exhaust out. When the piston reaches BDC we begin,

THE FOURTH STROKE.

The exhaust valve is opening at a fairly rapid rate, the piston is going up, and if the exhaust valve is not open a lot by the time the piston reaches maximum velocity, there will be resistance in the cylinder caused by excessive exhaust gas pressure. This produces conditions which are referred to as pumping losses. As the piston reaches the top of the cylinder, the end of the fourth stroke, you will see the exhaust valve is almost closed, but, lo and behold, the intake valve is just beginning to rise off the seat! At TDC at the end of the fourth stroke, both the intake and exhaust valves are open just a little. For this reason, this part of the stroke is called the OVERLAP PERIOD.

During the overlap period you will often find that both valves will be open an equal amount. This condition is referred to as SPLIT OVERLAP. On standard engines, the valves are only open together for 15 - 30 degrees of crankshaft rotation. In a race engine operating at 5 - 7000 RPM, you will find the overlap period to be in the neighborhood of 60 - 100 degrees (which also translates to more total duration)! As you might expect, with this much overlap the low speed running is very poor and a lot of the intake charge goes right out the exhaust pipe.

CALCULATING DURATIONS

Let us review the four strokes again and add some timing events to calculate the total valve duration. For illustrative purposes, we can discuss a good street cam with a 268 degree duration and 108 degree lobe centers. (The lobe center angle is the angle in camshaft degrees between full intake cam lift and full exhaust cam lift). As we discussed above, at the end of the fourth stroke both valves are open and the next stroke is the intake stroke. Referring to fig. 1, we see that the intake valve began to open at 26 degrees BTDC. The piston moves down the cylinder after the crankshaft passes TDC, and the valve reaches full lift at 108 degrees ATDC (lobe center). Note also that the intake valve is still open when the piston reaches BDC. We can start to add things up now. The crankshaft has rotated 180 degrees from TDC to BDC on the first stroke and the intake valve opened 26 degrees BTDC, so the total crankshaft rotation so far is 26 + 180 = 206 degrees. We started with a 268 degree camshaft so that tells us when the intake valve will close: 268 - 206 = 62 degrees ABDC. Note that even though the second stroke is the compression stroke, we see that it starts while the intake valve is still open!

FACT TWO: In the lower RPM range, the engine does not have any compression until the intake valve closes. As the engine speed increases, there is a ram or inertia effect which begins compression progressively sooner with engine speed.

Now, we compress the air/fuel mixture and ignite it at the proper time in order to maximize the push down on the power stroke, or stroke three. Remember, I said most of the cylinder pressure is gone by 90 degrees ATDC, and you can see that with our 268 degree cam, that the exhaust valve begins to open 62 degrees BBDC, that is, before the exhaust stroke actually begins. So adding again, we have 62 + 180 (stroke four) = 242 degrees. Thus at TDC at the end of the exhaust stroke, the intake valve has opened but the exhaust has not closed. The exhaust valve remains open for 268 - 242 = 26 degrees ATDC. With the intake valve opening at 26 degrees BTDC and the exhaust closing at 26 degrees ATDC we have a total of 52 degrees of overlap.

Now, with the basics down, we can start discussing duration, lift, lobe centers, compression, and cylinder flow.

VALVE TIMING EVENTS - ORDER OF IMPORTANCE

Let us now take the four valve timing events and put them in order of importance. The LEAST important is the exhaust valve opening. It could open anywhere from 50 degrees to 90 degrees BBDC. If it opens late, close to the bottom, you will take advantage of the expansion, or power, stroke and it will be easier to pass a smog test, but you will pay for it with pumping losses by not having enough time to let the cylinder blow-down. You must let the residual gas start out of the exhaust valve early enough so that the piston will not have to work so hard to push it out. Opening the exhaust valve earlier will give the engine a longer blow-down period which will reduce pumping losses. But, if you are only interested in low speed operation, say up to 4000 RPM, you can open the exhaust valve later.
The next least important timing point is the exhaust valve closing. If it closes early, say around 15 degrees ATDC, you will have a short valve overlap period. Less overlap makes it easier to pass the smog test, but it does not help power at the higher engine speeds. Closing the exhaust valve later, in the vicinity of 40 degrees ATDC, will mean a longer valve overlap period and a lot more intake charge dilution that will translate into poor low-speed operation. Some compromise must clearly be made to determine just how much overlap one needs to use. Many factors such as idle quality, low speed throttle response, fuel economy, port size, and combustion chamber design must be considered in making this choice.
A somewhat more important timing event is the intake valve opening. Early opening allows for a greater valve overlap period and adds to poor response at low engine speeds. Now, for the high performance enthusiast, low engine speed could mean 3000 RPM, but I would not consider such an engine as appropriate for normal street use! If you are not concerned about passing the smog test, then early intake valve opening will help the power output of the engine. That is, earlier valve opening will have the valve open further when the piston reaches maximum velocity and that, in turn, will increase volumetric efficiency.
I must stop now and ask you a question about your engine. If a 1500 Cortina head does not flow much air above 0.350 in. of valve lift, and it is possible to have the intake valve open that much by the time the piston reaches maximum velocity, WHY DO MOST PEOPLE THINK THEY WANT AT LEAST 0.500 in. VALVE LIFT???
Now, the last timing event is the most important, and the most critical to engine performance - THE CLOSING OF THE INTAKE VALVE. This event governs both the engine's RPM range and its effective compression ratio. If the intake valve closes early, say about 50 degrees ABDC, then it limits how much air/fuel mixture can enter the cylinder. Such an early closing will provide very nice low speed engine operation, but at the same time it limits the ultimate power output as well as RPM. Another problem with early intake valve closing that most people do not consider is that if you have a high compression engine, say 10:1 or higher, you will have more pumping loss trying to compress the mixture. This might even lead to head gasket and/or piston failure! These observations suggest that if you close the intake valve later the cylinder will have more time to take in more air/fuel and the RPM will move up. That seems simple enough, doesn't it? The later the intake valve closes the higher the RPM and therefore the more power, MAYBE? It turns out that if the intake valve closes past 75 degrees ABDC, you could lose most of your low-speed torque and if your static compression ratio is only 8:1, the engine will not be able to reach its horsepower potential. This should give you a better understanding of why the intake valve closing is the most important timing event.

CAM SELECTION REQUIREMENTS

So, now you ask, "What do I need to know to make a proper camshaft selection for my particular application?" The list is long. First of all, in what RPM range will you want power: 1-4000 RPM, 3-6000 RPM, 5-8000 RPM, etc.? What is the size of the engine? What are the bore and stroke dimensions? How long is the center-to-center distance on the connecting rod? How much piston pin offset is there? What is the static compression ratio? In the cylinder head, what is the maximum air flow (in cubic feet per minute or CFM) in the intake track with the intake manifold and carburetor installed? At what valve lift does the air flow level out on both the intake and exhaust valves? What is the percentage of air flow of the exhaust versus the intake? What are the valve sizes? What are the lengths and sizes of the intake and exhaust systems? Once you have this data, you should be able to make a logical cam choice; but sometimes you might have to face the reality that your basic engine parameters are wrong for the RPM range you are after. How can a layperson look in a cam catalog and make an intelligent choice? First the parts supplier must supply the proper information in order to help the customer choose the right camshaft for his/her application. But, in addition, you need to be prepared with the right information about your engine and what you ultimately want to be driving.

CYLINDER HEAD FLOW BASICS

Let us now review some basic cylinder head data that one must consider before selecting a camshaft. Most people will agree with the statement that larger valves are required for more power. But now we need to ask several questions. What happens to the volumetric flow rate (in CFM) when valve sizes are increased? What about the port velocities, both intake and exhaust? How are the exhaust and intake flows effected? IS BIGGER REALLY BETTER? It has been my experience that when you are dealing with a stock cam, say 250 degrees duration, it does indeed help to increase the valve size to get more flow through the engine. Low to mid-lift flow is very important on the exhaust valve and mid-lift to full lift flow is very important on the intake valve. Some engines respond to increasing the exhaust flow so that it almost matches the intake flow. Based on valve diameters, you will find that the exhaust flow is about 80% of the intake flow in your typical engine. Design guidelines developed by the Society of Automotive Engineers (SAE) suggest that the exhaust flow should be 75-80% of the intake. I prefer to be in the 80-85% range and port the head to achieve about 75-80% exhaust CFM flow compared to intake CFM flow. When using a stock cam, you can get good results even at exhaust/intake ratios of 90-95%. Such high ratios will also work in drag racing applications where the engine is intended to operate at wide open throttle (WOT) conditions. However, when a camshaft with more duration is installed in a "hot" street, auto cross, or road racing engine, a 90-95% exhaust/intake flow will over scavenge the cylinder resulting in wasted fuel and an undesirable reduction in torque. Now let's see how these comments have been translated into some popular 1600 Lotus Twin Cam street and racing motors. Valve sizes for various twin cam heads are summarized in the following table:


TYPICAL LOTUS/FORD TWIN CAM VALVE SIZES: Type : Intake Exhaust : Exhaust : % of Intake :
Standard Engine 1.530 1.320 86 %
Sprint 1.560 1.320 84 %
Racing 1.625 1.375 84 %
Brian Hart 1.690 1.440 85 %

In the above table, the standard engine is an early Weber head and the Sprint is a late Stromberg head. Flow measurements of the Stromberg, Racing, and Brian Hart heads are shown in figures 1 a-c. The Stromberg head (fig. 1a) was "cleaned up" but not fully ported, and the flow curves show a high exhaust to intake flow up to a lift of 0.100". This flow ratio then levels off to about 80% for higher valve openings. Note that the intake flow doesn't increase much past 0.400" lift, and the exhaust levels off at 0.400". The racing head (fig. 1b) is a Weber that has been prepared (supposedly), but you can see that it has a very poor flow ratio at low lifts where the exhaust flow actually EXCEEDS the intake flow! Things look better above 0.150" lift and the intake flow is good past 0.450" lift while the exhaust flow levels off at about 0.400". Finally, the Brain Hart head (fig. 1c) shows some really deep breathing capabilities! A lot more CFM overall, and great intake flow up to a 0.450" lift with the exhaust good to 0.400".

Most push rod and twin cam cylinder heads flow very well up to 0.350" lift, but flow increases really start to level out beyond that lift. The larger the valve the higher the CFM is over what you normally expect, and you can see that the twin cam head will flow well even above 0.400" lift when it has been reworked by increasing the valve sizes, grinding, polishing, and blending the valves and ports. The bottom line is clear: a well developed cylinder head on an engine will really pay off in increased horsepower. However, as I have said before, the individual making an engine modification has to be realistic about where he/she wants the power range.

COMPRESSION AND DURATION

Just about any engine would benefit from a prepared cylinder head, a good exhaust system (with a relatively small diameter for street use), and maybe a little larger carburetor. As you increase the RPM band, you'll need to increase the compression ratio and add some more duration to the cam. The more duration you add, the more compression you'll need and that combination will increase the upper mid-range and top-end power. It is very important to keep your combinations balanced; for example, you can not use a 270 degree camshaft with 8:1 compression. 9.5:1 would be a lot better. Conversely, you can not have 10:1 compression and use a cam with only 250 or 260 degrees of duration! As soon as the duration is above 270 degrees, the standard exhaust system will likely restrict the breathing ability of the engine. As a result, it may become difficult to make the idle mechanism work properly due to reduced vacuum and extra exhaust back pressure.

ELGIN CAM DESIGN PHILOSOPHY

You probably have figured out by now that I am not an advocate of extra high lift, unnecessarily long duration, or very high compression for any street driven car. I prefer instead to use maximum velocity in the camshaft design which allows my cams to have more duration at 0.050", 0.100", and 0.200" lift compared to the "Brand X" cams you might get from other sources. As a side benefit of this design choice, it turns out that when you have more duration at 0.200" - 0.300" lift and not as high a cam lift, you end up with a cam lobe with a rounder nose radius which will support higher valve spring loads and therefore will last longer than a "pointed" high lift cam. I learned a long time ago that dwell on the nose, or top, portion of the cam lobe is equivalent to lift provided that you have the valve open far enough when the piston reaches its maximum velocity. On a normally aspirated engine, I have never seen power increased by adding valve lift above and beyond the flow capacity of the head.

You now have all the info you need to make the important performance enhancement choices appropriate for your own application - so there is not much more to say except HAPPY TUNING.

By: Dimitri N. Elgin


----------------------------------------


Do you agree with his theories, and do you feel that when the exhaust valves closes is the most important aspect of your cam designs? Also, the one thing I noticed about you cams is that the LSA seem to be a lot closer than most cams on the market. You seem to really like the 108-111 range for cams whereas most cams these days are 112-115 @ a minimum. You cams look to have quite a bit of overlap. In the car you are doing cams in, do they have quite a bit of lope, how is the low speed drivability, etc....

Thanks...

93PONY

Ouch.
Your posts are giving me headaches! LOL
I have not consulted with Elgin cams on their theories.
Ed Curtis (www.flowtechinduction.com) is one I use theories from. I combine his & Brian's theories & put them to the test in my cams.
IMO the exhaust opening is not the least as Elgin states..... For too long the major cam companies out there have stated that the exhaust lobe is the least important....well, they're wrong. & The cams I design are proof of this. The most important lobe in my cams is the exhaust. Specifically the exhaust VE's. Open the exhaust too early & you lose heat energy & velocity through the exhaust runners....you also get significant reversion of the exhaust gasses which kills power. Open the exhaust valve too late & you won't get all the gasses out of the cylinder which contaminates the intake air-charge & drastically affects power. No...the exhaust valve opening must be timed perfectly for every thing to go correctly in the rest of the cycles. Exhaust valve opening is the most important VE in my cams. Followed by intake closing, then the overlap events...no specific order of importants on those two (EVC, IVO). To do a cam correctly ALL VE's must be perfect for the setup in order to get the most out of a profile. VE's are most important (.006, .050, .200, etc), followed by ramprates of the lobes. It's in this order that I design my cams. Never lobes first.

Overlap = power. It also tends to give lopier idle. My cams lope less then most others out there....even with more overlap. Simply because I choose good VE's.

Lobe profiles vary greatly...even in just the XE line of Comps. Depending on low, mid, & high lift intake to exhaust ratios determines where I have the cam intake or exhaust bias. For instance, for a combination (intake, heads, exhaust) that has an intake to exhaust ratio of 70% at .300 & 85% at .500 I'd likey go with 2 lobes that have radically different ramprates....such that at .300 (vavle lift) & below the cam is exhauast bias, but above that the cam starts to become more intake bias.

I also use the fastest ramped cams I can find in N/A setups....gives the most flow area possible...& actaully helps with idle qualities over a 'larger' cam. .006 valve events are very important. This is the true opening & closing of the valves. .050 #'s are good for calculating how the motor will respond as there is very little headflow below .050 (at least on the intake side of an N/A motor).

Donovan

I use Elgin Cams exclusively. I will not use any off the shelf cam. I have my heads, manifold and carb(throttle body)flowed all together and then give the info to John at Elgin cams and they build the cams. I also use Allan Lockheeds Engine Expert program to design the engine. Allan Lockheed and Dema Elgin teach a seminar that is really good on building engines and specing the right parts the first time. Good luck.

Louis

iTrader: (7)

Brian at Hitech likes reverse splits in general.

I have a friend locally here with a 5.0 notch that has a reverse split from Brian. This is one of Thunders main points with reverse splits is the fact that Al Cordas S/E car is using a reverse split cam from Brian at Hitech.

Just adding info

Joe Bronikowski

iTrader: (1)

Interesting discussion.

93pony, what do these tighter LSA's do to the cam's rpm range, especially on your "smog" cams? Common wisdom is that tighter LSA will narrow the power band, and 109 is a lot less than 114, or 117 (LS6).

For example, for these two cams

212/210 109LSA .571/.566 w/1.7's
218/218 111LSA .578/.553 w/1.7's

at what rpm would you suggest shifting at the strip?

93PONY

With a smogable cam you can only go so tight on the LSA. Basically -4 to -3 overlap is it.
In general, tightening the LSA on a cam will narrow it's powerband....& push it up. Hmm...how to put this.

The LS1 is intake limited, therefore it is RPM limited. Putting a cam in that is ment to peak at 6800rpm is just a waste of lobe. With the current intake selection (LS1/LS6) the motor can not make power that high in the RPM. So, tightening the LSA on a cam like that would boost power in the mid-top-end & keep most of the power in the usable RPM range of the motor.

I tighten up the LSA to do just that....make the most power under 6200rpm since this seems to be where most LS1's make peak power....reguardless of cam specs.

J-Rod

FlowTech obviously is doing a lot on the Mustang front. We run in a lift limited class that is carburated (not EFI) so they may have some interesting things to say.

One thing I did read on their site is: General Motors customers using the "StreetBeast" and "Max-Effort" series of custom hydraulic roller camshafts in their LS1 Camaros and Corvettes have seen rear wheel horsepower and torque numbers that make them act like stroker engines.

Just ask around the various Mustang and LS1 web sites and we're sure you'll find plenty of satisfied FTI custom cam users.


Not to be disrespectful to them, but before your post I had never seen them mentioned on this site, or on any of the other LS related sites I visit. Are there sites they tend to frequent where one could look at their customer's results.

Thnaks for the clarification of which valve events you feel are most important. I noticed in the cam that you spec'd out for Crash that you are opening the exhaust valve earlier then his "theory" cam.

Valve events comparison:
Your cam:
IVO: 2 BTDC
IVC: 50 ABDC
EVO: 49 BBDC
EVC: 1 ATDC

That cam:
IVO: 5 BTDC
IVC: 41 ABDC
EVO: 52 BBDC
EVC: 0 (TDC)


Here is another one:

When the intake & exhaust is bolted the the LS1 heads, the intake to exhaust ratio is well over 75%.
I like heads with good flowing exhaust. Makes for a cam that can make a ton more power then a head that needs exhaust bias lobes....given the same overlap & intake closing event.

Crash, here is the valve events for the Brian cam:

230/228 114LSA 114ICL
IVO: 1 BTDC
IVC: 49 ABDC
EVO: 48 BBDC
EVC: 0 (TDC)

1 degree overlap @.050 lift.

If you want, I can spec you this cam using Compcam lobes. That way you aren't waiting for Brian to place the order (sometimes it takes him a few weeks) & it'll save you a little $$$. Comp charges $400 for a custom.

Just a little interesting info.... When lobes are placed on larger/smaller size cam cores, they grow/shrink accordinly. That 230/228 would be a 226/224 in a Ford....or a 224/222 in an LT1.


In both cases for EVO (the one you feel most important) you are @ 48 to 49 degree BBDC. Is this a rule of thumb for you in the LS1 cams or is there more to the forumlas you are using?

J-Rod

One other thig to add to that discussion. I know we have been talking about I/E percentages. Let me cite two cams from GM I know you are familiar with. The first is the



The second is the World Challenge or 'Gib' cam

88958606 Roller Camshaft "Gen 3" Showroom Stock Design
This hydraulic roller camshaft for RPO LS1 or LS6 was designed for showroom stock road racing. It requires the use of 2002 and later LS6 hollow stem intake valves P/N 12565311, hollow stem - sodium filled exhaust valves P/N 12565312, and valve springs P/N 125565313. It features .570" intake and exhaust lift, 251 degree exhaust duration at .050" and 239 degree intake duration at .050".

Technical Notes:
• Center line of intake lobe means M.O.P. or maximum open point, determined across nose of lobe.
• Lobe flank is not symmetrical - for best torque set intake to TDC@105 degree and for best power set intake to TDC@106.5 degree.
• Cam timing @ 0.050" tappet lift (timed @106 degrees intake to TDC)
• Exhaust opens @ 51 degrees and closes @ 20 degrees with duration at 251.
• Intake opens @ 12 degrees and closes @ 47 degrees with duration at 239.

The Gib cam is designed to work with the GM CNC heads with LS6 springs. The ramps aren't crazy since the valve springs aren't crazy. Here are the flowsheets on the GM CNC heads

Intake GM \ LPE LS6 CNC 2.00/1.500 250CC Intake - SDCP numbers
.050 -
.100 65
.150 -
.200 138
.250 -
.300 214
.350 -
.400 261
.450 -
.500 292
.525 295
.550 285
.575 -
.600 282
.625 -
.650 -
.700 -

Exhaust
.050 -
.100 58
.150 -
.200 113
.250 -
.300 157
.350 -
.400 191
.450 -
.500 210
.525 212
.550 214
.575 -
.600 218
.625 -
.650 -
.700 -

As you can see I/E pecentages is .68 - .77 with no intake in place. In speaking with someone who was involved with the design and selection of this cam, GM spent well into the 6 figures (i.e. $xxx,xxx.xx dollars) in just dyno time alone coming up with this cam. This was the cam (out of many, many) which made the power they needed. In full race trim, this cam makes 450-470RWHP. I see that GM also made their EVO close to where you are making yours.

Anyhow, they kept the exhaust side smaller which may have been an SCCA mandate. But I wanted to point this out also.

The subject of reverse splits vs symetrical or standard splits has been covered, but this is the first time I have seen some theory behind when to have your valve events. I wil admit I am in the standard split camp. But, you make a very compelling argument. I just need a bit more on how the VE's are being determined for me to be more comfortable with the theories you are proposing.

I am not trying to go grind my own cams or steal business away from you. But in the same way folks beat on LG when he wouldn't release a cam card with his camshafts, it is the same way with this.

I understand what you are saying. My question is why...

93PONY

I choose the EVO based on the IVC.
I then pick how much overlap I want in the cam.
From there I choose the EVC & IVO.
These give me my VE's for a particular setup.
From there it's just a matter of choosing the right lobes. The LSA & ICL are just calculations....just a byproduct of the VE's I choose if you want to look at it like that.
As I said before I choose the lobes based on the flow charateristics of the motor. Intake to exhaust ratio with stub pipe on the exhaust & intake on the heads, whether boost or N2O is involved, racewieght, gearing, etc, etc.

*interesting side note*
For best ET/MPH in the 1/4 one should setup their gearing/tire package to end the 1/4 mile just past peak HP.

maddboost

iTrader: (11)

Well I want to thank all you guys for having a good high level discussion like this on cams. Its nice to see that there are some members on this board who can have a good high level discussion without vendor bashing or dyno crap getting in the way. While I will admit that a great portion of your posts I had trouble understanding none the less I feel I have learned a few things from it. So thank you again.

SStrokerAce

iTrader: (2)

First J-Rod, these are the longest posts EVER. I'm with Pony shorten them up a little.

O.k. given this info, I come up with the cam specs as this:

239/251 .570/.570 107.5 ICL/105.5 ECL which is 106.5 -1

That's with the opening and closing points you listed.

Now when they change it over too the 105 ICL for best TQ we are looking at the cam +1 deg (Advanced)

so we get:

Intake Open @ 14 and Closing @ 45
Exhaust Opening is @ 53 and closing is @ 18.

That seems to favor the TQ curve below 5800 and the HP set up favors the area above that, but not by a large amount.

I would love to know the .200 durtaion numbers on this cam, just to get and idea of the lobes. I doubt that they are very aggressive.

The overlap area of that cam @ .050 is 32 deg, which is indicative of the high RPM use it is intended for.

The valve train they use is a pretty important here too. There is alot to be said for the Ovate Wire Beehive spring design and with the addition of hollow and sodium filled valves it makes this a very controllable valvetrain without the use of alot of force from the springs. Now add in some Ti retainers and you have about the lightest steel valve Small Block Valvetrain ever.

Which brings up some other points, the use of the 26918 springs I think is the way to go. About the only bad thing about them is that they had a bad batch of springs. The good things all have to do with the shape of the springs. The beehive shape allows you to use retainers that weight in at 42% of their dual spring counterparts. That's a few grams, but in the valvetrain that is a big percentage, and it's a big amount out of the valves. Throw in the fact that the springs are 63% of the weight of a compareable dual spring and you take even more weight out of the valve. (BTW the retainer and about 1/2 the sping weight count in the calculated total weight of the valve.) The smaller top of the spring than the bottom probably makes this % even higher since the top of the spring is what is counted.

One more thing that the beehive shape adds is that the valve spring has no major resonance frequency. This is one thing that will cause dips in the TQ curve and odd valve control at different RPM. The beehive spring does have resonance freqencies but they are much small because there are more of them. This all adds to a better TQ curve and more average power.

Now the only bad thing is that the 26918's don't have a super amount of valve spring pressure for the XE-R lobes, and the lack of valve control is worse than the extra weight of the 977's springs. The spring rate and the seated force goes up a good amount with the 977's but then again you are adding weight. One reason why it's a REALLY good idea to run Ti retainers with the 977's.


I'm also with J-Rod on the standard split cams, all though it is interesting to see that Al Corda is running a revearse split cam. Due to the restrictions he has on his motor, that would give us some reasoning why. He certainly can get more air out of the motor than he can get in.

A few other things I have noticed and reasons I'm in the standard split camp. The most imfamous split pattern cam for the LS1 is the LGX5 cam. As we have seen it makes some awesome HP and TQ. One reason we see it work well with Absolute Heads and LG's heads is probably because they flow so well with the LS6 intake on. The 305cfm to 282cfm with the intake on is not that bad for a production intake. The crazy thing is that just because the head flow is less with the intake on doesn't mean that the extra head flow is not going to help. If you increased that headflow without the intake to 330cfm and still had 282cfm with the intake on the motor would make more power.

We also see a 72-75% E/I ratio without the intake, which is where I start. Even with the intake flowing what it does, on the motor we still need a split to get a Total E/I ratio of around 75%, and I usually like 75-80% for NA motors. The Total E/I ratio is calculated out of Valve Area, deg*sq in for the intake and exhaust. That number is calculated from valve size, cam profile, flow curve and duration. It's not something I do manually, but I use a computer to determine that. It's a more complicated E/I calculation than one with just flow charts. When I look at a cam like the TR230 as a tradtional split cam I get a lower Total E/I ratio of around 71-2%.

So if we look at at the TR230 revearse split cam and compare that to a cam with the same intake duration but instead of 6 deg less exhaust duration we add 6 degs more we will move from about a 72% Total E/I to a 76% Total E/I. Then if we get the overlap are to be about equal we can compare the two cams a little more. It will work out that the standard split cam will make more HP and the revearse split cam will make more TQ, even with the same 5 degs of overlap @ .050. Considering traction is a problem for some guys on the street I would go with the standard split. On the other hand the revearse split cam with more TQ will make a better A4 cam.


J-rod ingnore my long post point above, I like writing too.

Bret

SStrokerAce

iTrader: (2)

I agree here, I learned more on a .050 based duration scale so I think that way when I start and end up tweaking the duration and LSA/ICL/ECL to get me where I want to be. Basically what we are doing is getting the right IVC and overlap for the particular combination.

Interesting way to go about it. I work more with the lobes and the valvetrain budget/parts I get to work with. When it is unlimited then yeah sometimes a more aggressive lobe works better, but sometimes not. The bigger thing is the life of the parts for me in the lobe selection, the more aggressive the lobes the harder it will be on parts.

I hear you on the car and application for the rest of it. There is a big difference in a A4 cam and a M6 cam for the same motor. Normally I like more gear too, 4.10's are usually a pretty good place to start and they can always handle less LSA just because the car will drive around at higher RPM. Then again it will also make more TQ at high rpm so gear likes that too.

Bret

BYBYC5

i asked befor in a diffrent thread and email but i figure scince this is a cam disscussion, can you all evaluate this cam for me. i gotten several opinons about it but just looking for more, im looking for 6300 and below tq/hp monster, 11.5 CR is what we are working with as well.A4,3600 verter and 373s, tuning is not an issue..thnx
adv.282/282
.050 224/224
IVO 6 Btdc
IVC 46 ABDC
EVO 38 BBDC
EVC -2 ATDC
an adjustable timing set is instaled as well.

Reboot

iTrader: (5)

I think they would need the LSA and ICL of your cam to give you a accurate assessment.

BYBYC5

oops my bad...
adv.282/282
.050 224/224
IVO 6 Btdc
IVC 46 ABDC
EVO 38 BBDC
EVC -2 ATDC
110lsa 106icl

Louis

iTrader: (7)

Just another tidbit-

The 239/251 cam from GM uses the 02 LS6 springs, and another earlier form of beehive springs back in 00. It does have the lightweight valves, but we all know what that spring can handle.

I have a graph of a 450/411 of a WC car, Ill see if I cant find it. Power is flat from the peak, doesnt really fall off.

Brian from Hitech did a reverse split cam for Pirate Racing ( World Challenge Team) back in 01. It did have a holly stand alone, but supposedly made upwards of 470 to the wheels. Keep in mind the car uses a 5" triple disc clutch thats 1/4 the weight of a stock unit.

J-Rod

Ok, I know I am long winded...

Anyhow, my thing is I am always willing to listen as I may learn something. I have seen lots of info on reverse splits but I have never seen any math on it, or for that matter some math on how to come up with a more optimal cam selection. I'm all for being able to calculate my own VE's, or at least understand what is going to make one cam work better than another. So, I am all about good theory, and good practices.

Anyone else have some math or theories they'd like to share on the subject?

I'd be intersted to see a Campro on the Cartek X cam since it is also one of the heavy hitters out there. It'd be interesting to see what the valve events are on their cams...