Friendly Freddie

I REALLY wanted to drop this bomb in the "advs/disadv of rod length" thread , but I figured it might ruffle a few feathers by disrupting the present topic of conversation (although its changed about 4 or 5 times already ). Its hard to get really good information about this from true experts.

Moving on , I have a 358 inch LSX engine in my race car. It was originally assembled for use in the LS1tech series extreem mod class which was an all motor class. We kept it under 360 inches to get the wieght break. We soon found out that to get this little engine to 60ft , it needed so much converter that it was no longer efficient on the big end of the track. Faced with having to put a jerico(sp?) in the car or do something else with the engine, I gave up and put a plate system on the car and decided to have some fun. The camshaft was sourced from LSM , and ground specificly for NA use. Is there a possibility I will see a gains from a cam change if I get one targeted towards N20 use? If so, why? and what are the differences between an NA specific and a N20 specific cam.

I know N20 is a dirty word for "real engine builders". I also realize that this thread is kind of "self serving" , but there is not a whole lot of really good info out there on this topic. I think all of us N20 addicts would benifit greatly from a truely intellegent conversation on this subject.

SStrokerAce

iTrader: (2)

It's probably also going to change the header requirement and possibly the head gasket thickness.

How much N2O are you looking at here? If it's not a huge shot then there is not much the cam itself is going to make huge changes in.

FWIW the guys on here don't know nearly as much about cams as the guys at LSM. Them and a few other guys out there are some of the best in the bussiness.

Bret

Friendly Freddie

I already have the largest Header available without going to a custom set (1 7/8" stepped to 2" with 3.5 inch collector) . I have a 300 pill in the plate and use a progressive controller. I have already backed off the timing in an appropriate manner , installed the correct plug etc.. I have been told that with a 15:1 compression ratio, I need to have a really tight LSA to help bleed off cylinder pressure to keep it alive.I have also been told if I go with a wider LSA it will make more power. I just want some info to try and make an informed choice , and understand how changes in the camshaft design affect a nitrous engine (if it is any different than an NA app).

SStrokerAce

iTrader: (2)

I've never understood how LSA bleeds off any cylinder pressure.... the IVC point does that and if you go tighter with the same LSA it increases the cylinder pressure.

With a 300 shot, yes you will need more camshaft, mostly more LSA and more exhaust duration.

Al from LSM is on here sometimes, pretty smart dude. Maybe he will say something...

BTW what's the rest of this combo? If you want to keep it private PM me.

Bret

Friendly Freddie

No need to keep it private everybody has seen the car run.

Here is a component list for the long block (Long block assembled by LME)

6.0 litre block with custom oiling system.(ext oil press reg and remote mount oil filter)

GRP aluminum rods

Wiesco custom pistons,with hellfire ring set (15.5 to 1 comp ratio)

LSM solid roller cam (264/268 .705 .705 110lsa)

Lunati solid roller lifters

CV dual taper 3/8 pushrods

Cylinder heads are 6.0l castings that have been extensivley worked by Trevor Johnson. They feature 1.590 PSI springs , Xeldyne 2.100 ti intake valves and 1.67 ti exhaust valves. The rockers are shaft mount .50 offset jesel j2k's. Combustion chambers were welded to create a custom shape, and increase compression. Obviously a 2.100 valve wont clear 4.00 bore , so the heads are offset on the deck 50 thou to correct this issue.

GM perf parts carb style intake also worked by Trevor johnson , with fabricated alum elbow and 90mm throttle body.

I've had problems with head gaskets on this engine from day 1 and I am in the process of swaping over to a new set of heads , and stepping the head studs up to 1/2". I figured why not get the cam program squared away while Im at it. I just don't want to go the wrong direction with it and not see the gains I am looking for. I would like to pick up 100rwhp. I am hoping the right cylinder heads , a new cam , and a direct port system will get me there.

CamKing

I'd go with a longer exhaust duration to keep the temp down.

At what RPM will you be using the NO2?

Friendly Freddie

I usually activate the system right off of the trans brake @ 5K and shift around 8.4K I have hit the limiter at 9200 and it never seems to quit pulling. This is one of the things that got me so interested in the discussion going on in the other thread. I am afraid of going to a larger cam and more cylinder head because I don't want to have to spin this engine 10k to see the increase in power. I am starting to wonder if maybe I am at the very edge of what an engine this small is capable of making in a useable rpm range.

CamKing

I'd look at running a smaller intake lobe, or at least tightening the intake centerline to make the cam more efficient at the lower RPM's.
The NO2 has the top end handled.

ProdriveMS

If you haven't yet, give Steve Sr. a call. We may even be able to regrind that cam to the new specs if it isn't too large of a change.

Al

Friendly Freddie

Very cool , thanks for the advice!

anybody have anything to add?

SStrokerAce

iTrader: (2)

With that setup there is a lot of things you can do. The intake and cam combination is interesting, but the intake can use a TON more work to get it where I would want it for that application.

I'd throw more converter at it with that cam, you have too much in there on average and the RPM band is too wide.

As for a N2O cam that's another story.... but the motor looks good to me pretty similar to one I have in the shop except we have a LS2 block, a little lower compression and a much different cam. Oh yeah and some Darts that are heavily worked over from AirFlowDevelopment.

I'd also look at the Wilson elbow it's going to work a bunch better than a fabbed one with some work on the inside of it.

How much power are you making now and what's that puppy run?

Bret

Friendly Freddie

Thanks Al , I will do so. I just thought I should have all of the other specs inline before I called. I wanted to make sure I could answer any questions he might have for me about the set up (hardware), and what I was trying to accomplish.

Do you guys keep detailed record of cams that you grind for your customers? I don't know the details of the valve timing events , lobe profile , etc... I only know what Brian at LME gave me for specs verbally. It would be neat to document the changes made to see what effects they have in this real world application.

Friendly Freddie

Bret , thanks for the advice. I think when I get ready to do something with the cylinder heads I will give you a call if you don't mind. The intake has been heavily modified it looks very similar to a vic jr internally, and the elbow is fabricated from 4" od aluminum. I was told the heads and bore size were the limiting factors at this point. I would tend to agree more with Erik K and say that RPM seems to be a huge issue , IMO The valve train is just not gonna live for very long above 8500.

The car has made as much as 540 at the rear wheels when I had it tuned for NA use. This is through a Rossler TH400 (lightwieght billet rotating assembly) , and a Strange 9" with 40 spline axles. Now, with about 16 degrees of timing it makes in the mid 490's on the motor and just a touch over 820 with the 300 pills in the NOS bigshot plate.

I have only run the car a few times in the 1/4 , the first pass off of the trailer at southern shoot out in san antonio it went 8.73 156mph , and backed it up second pass with an 8.76 @ 154. If I could keep the heads on the damn thing I would stop all of this talk about selling it. I'm gonna give it one more try , and see how she goes without the weight in the car.

ProdriveMS

Yes we do, it's based on the cam identification number(CIN) stamped on the end of your cam. Any changes made to a cam gets supplemented to that CIN in our database. We spend the extra money to case harden our cams as deep as our heat treater can go for events such as these. Now, if the profiles need to be changed slightly, we can regrind the cam without breaking through the case hardening. It's all assuming that the change isn't too great of course.

Sr. has been doing this for most of his lifetime, and can rattle off cam specs off the top of his head that would take me a while to calculate. I have an idea of which way you should go, but I would rather not give my opinion, but let you talk to him instead.

Al

SStrokerAce

iTrader: (2)

With the N2O, you probably have a issue with the deck thickness of the heads and a issue with the quench that's giving you the head lifting.

I agree that the bore is really a limit. A 4.0" bore is better than a 3.900" bore though! Trevor does good work, I don't think it has any issues with him but I do think the issues are the castings themselves.

As for the intake when I say HEAVILY modified it's got about 3lbs of weld in it and doesn't look as much like it did. We have talked about a few different things to try but I think that were we are starting from will be fine. We have talked about sheetmetal intakes and L92 heads as well, but I don't think a OEM casting will have enough deck thickness for ya.

I was telling these guys in another thread about how much pulling timing hurts power, and I'm guessing you pulled 6-10degs out of yours. I can believe that 50hp loss though. How much were you running just for reference for the other guys.

I have some ideas of what you would want to do with the cam as well to get everything to work with the intake and the N2O.

Bret

racer7088

Friendly Freddie,

I would back way off of the compression and run a lot wider LSA right off the bat if you are going for more power with the nitrous. Tightening your LSA BUILDS compression and certainly does NOT bleed any away! Anyone telling you that you need to tighten LSA as you add compression is just plain wrong or doesn't understand camshafts very well. Tightening LSA is for classes where you can't make good compression and/or where you have tons of exhaust flow and low backpressure compared to your intake capability.

Tightening LSA opens the exhaust later which hurts power on NOS and it also closes the intake earlier which increases cylinder pressure down lower in the rpm band but may even reduce power overall depending on the engine. With the compression you have I can't imagine needing too tighten LSA or advance the cam much at all! Tightening LSA also increases overlap which is also NOT where you want to go on a nitrous engine unless you have huge exhaust and even then 110 is too tight. It is just increasing reversion.

I would have a cam probably much wider in LSA with a fairly large split to the exhaust side in duration. You need to size your exhaust lobe such that it can handle along with your headers and exhaust system the power you are aiming to make on NOS. The cam you have is not one that is going to make big power on NOS probably. Your intake lobe is big enough but certainly not huge and you shouldn't really make power as high as you are turning it anyway.

Also If you could leave on a little less NOS and phase in the extra NOS at even higher rpm your gaskets will live longer. Most people spray too much too soon and the cylinder heads simply lift and /or detonate. The LS1 just isn't the greatest on the head gasket situation that's for sure! Spraying 300 at 2500 rpm is 600 ft pounds more tq and spraying 300 at 5000 rpm is 300 foot pounds more tq and spraying 300 at 7500 rpm is only 200 foot pounds more tq.

racer7088

Bret,

NO one at a cam company light years away knows as much as the people really running these engines and really using those cams. NO offense to either of the places you mentioned as they know their products totally from top to bottom and are absolutely top notch but until you've seen several cams all from dedicated race cam shops and you see them against each other and then you see the next batch of cams and then you see the next batch of cams you will know that no one knows exactly the best cam for any situation other than the engine builders testing it all for real.

I've seen some big cam guys tell us that they knew we were on the wrong track and we used their cam and lost power and went slower and then went further the direction we were going and picked up and went faster. Now when you have guys sitting down and running engines on dynos and on the track for twenty years like they do in Pro Stock or NASCAR and running the valvetrain on spintrons for thousands of hours with every conceivable rocker and pushrod and valve spring combination then you'll find someone that can tell you a whole lot about that exact combo but they still might not be able to pick as good a cam as you could for your car.

I can't tell you the hundreds of situations where a cam company promised people I know to pick them up and did not. I'm not saying that the problem was just the cam but I've seen one too many "cam gurus" in my lifetime already and most don't know a damn thing and I am NOT talking about anyone in particular because I actually like most of the "cam gurus" I know but I think you know what I mean! The guys from LSM and Camking are experts in their field of camshaft design and manufacturer and are NOT what I am talking about in general as well so I am not talking about them.

LS1Tech is quite simply the most cam obsessed and cam driven web site on the planet! People on this site have routinely told me how they could tell the "difference" between cams that were actually the same! I just don't say anything anymore.

SStrokerAce

iTrader: (2)

I would have to agree with this! That's a good laugh as well.

Bret

Friendly Freddie

Brett, Trevor seems to think that part of the problem with head gasket retension in this particular application is due to the fact that the cylinder heads have been welded (pretty extensivly). This has compromised the casting by giving different expansion characteristics to the welded and untouched portions of the deck. Add in the thin factory deck, and head gaskets become a problem.

I have a set of AFR castings that started life as "porters castings" Trevor started on them for another project but never finished them. What is your opinon on these casting as far as deck thickness and longevity in this application? Or maybe I should just get a set of big chamber 4 inch bore ETP LS7's ?

I think a lot of the things that you guys are bringing up, each play a minor role in the issue that I'm seeing with the head gaskets. I know a different set of cylinder heads are a must , as well as a camshaft revision. Now I just need to make the decisions as to which cylinder heads , and get the guys at LSM to fix me up on the cam change.

P.S. the timing was around 24 or 26 to begin with. When I Speed density tuned the car and added the plate I dropped 10 degrees of timing.

SStrokerAce

iTrader: (2)

Yeah, the welding definately doesn't work to help the integrity of the heads due to it's change of the heat treatment. Welded chambers and N2O don't go together.

As for the other stuff, I'd have him finish the AFR's for you. They are going to require the least amount of change to the motor and most likely solve your problems.

Bret