Who makes the strongest LSx crank???

[Quick Carl]

Originally Posted by Phil99vette

We already have a good dry sump. Its initally setup for a big block chevy, 5 stages, divider pan. We've got more than enough volume and oil pressure. Oil pressure on the big end is 110-120psi.

We're going with a Sonny Bryant crank, 2 custom pieces on the block and a couple other changes to see if we can get it to live @ 2500hp and 8500-9000rpms.

Good choice on the crank, the Sonny Bryant cranks are flat tough. We went to one in a splayed rod Twin turbo V-6 set-up and it ended all our issues. The other cranks would flex so badly that the counterweights would rub the side of the aluminum rods at around 1300-1400 HP. Keep the rod journals at 2.100 with big radiuses and get a set of MGP rods to help keep the bearings in it and kill some harmonics.
The problem is that you'll forget you ordered it by the time it shows up.

[TT610INCH]

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[JL ws-6]

Originally Posted by Fireball

with stroker cranks...that alot of weight being thrown around pretty fast...

I have a 4 inch crank in my motor but it's only seeing 7000 going down the track, every now and then in the burnout box it might jump to 7500 if I whack it too hard to get the tires spinning.

According to my calculation, the forces that are seen at 7500 vs 9000 are a HUGE difference, I cacculated the stored energy in a 50 lb 6 inch diameter weight that was sipnning at 7500, then at 9000, and that # alone tells me that the potential of the RPM alone being the issue is very high.


There's no way to make the power without that kind of RPM is there? I assume no, but I have to ask.

What about the tranny... input shaft speeds like that cause any problems there?

[Fireball]

Originally Posted by JL ws-6

I have a 4 inch crank in my motor but it's only seeing 7000 going down the track, every now and then in the burnout box it might jump to 7500 if I whack it too hard to get the tires spinning.

According to my calculation, the forces that are seen at 7500 vs 9000 are a HUGE difference, I cacculated the stored energy in a 50 lb 6 inch diameter weight that was sipnning at 7500, then at 9000, and that # alone tells me that the potential of the RPM alone being the issue is very high.


There's no way to make the power without that kind of RPM is there? I assume no, but I have to ask.

What about the tranny... input shaft speeds like that cause any problems there?

since drag radial cars are pretty much limited to 30" tires, you need pretty good rpm to turn 200 mph if you want to be a top dog

[Robin L]

Originally Posted by Fireball

since drag radial cars are pretty much limited to 30" tires, you need pretty good rpm to turn 200 mph if you want to be a top dog

That is why most drag radial cars run a 3.25 gear ratio.



Robin

[JL ws-6]

Fireball I understand that... my thoughts were on the rear gear like Robin stated, and then the possibility that maybe a 3 speed so teh car will get out of the hole good woul d work better. I know that TH400 isn't really gonna be reliable enough though... you guys might be at the point where a bruno/lenco style tranny is needed.

[Frank02L]

My truck went 1.44 60' with 3.25 rear gears and a 1.80 PG and that was when it was running bottom 10 teens. (a little over 3600lbs) I dont think these guys need the 1st gear when you are talking about being able to make 2-3x's the HP. I had put 3.25s in it to soften the 1st gear on the TH400 that I never got reliable.

[JL ws-6]

I think alot of these guys are running 1.69 powerglides, and they are running a 30 inch tall tire. Plus to run the #'s they need to run they need to be cutting 1.28 to 1.25 60 foots I think.


To get a car with a 3.25 rear gear and a 30 inch tire to 60 foot in the 1.2x range, plus being a turbo car that you can only build X amount of boost on the line with starts getting a little difficult I'd think.

With a 2.x first gear they could run a 3.0 rear gear and not have to spin so many rpm's to get to the mph needed, and the cars would probably leave better.

Question is, can the power that's needed be made with less RPM, or is that where the motors/turbo's need to be?

[Phil99vette]

Anyone can do the math.....
30" tire
1.0 final drive
3.50 gear
195mph = 7650 driveshaft RPMs
8% converter slip
8300 engine RPMs

200mph = 7850
8500 engine RPM

So the guys doing the LSx testing saying it will live @ 2000hp but are limiting the testing to 7000 is merely that a test. We're not racing the motors on a dyno. If the LSx was built like a small block chevy or a Big Block chevy we would not have the problems everyone is seeing.

[Phil99vette]

Originally Posted by Robin L

That is why most drag radial cars run a 3.25 gear ratio.



Robin

Who makes a Big Pinion 3.25?

[Fireball]

Originally Posted by Phil99vette

Who makes a Big Pinion 3.25?

they probably only have a standard gearset...pro gears only go to 3.40

[Frank02L]

Originally Posted by JL ws-6

I think alot of these guys are running 1.69 powerglides, and they are running a 30 inch tall tire. Plus to run the #'s they need to run they need to be cutting 1.28 to 1.25 60 foots I think.


To get a car with a 3.25 rear gear and a 30 inch tire to 60 foot in the 1.2x range, plus being a turbo car that you can only build X amount of boost on the line with starts getting a little difficult I'd think.

With a 2.x first gear they could run a 3.0 rear gear and not have to spin so many rpm's to get to the mph needed, and the cars would probably leave better.

Question is, can the power that's needed be made with less RPM, or is that where the motors/turbo's need to be?

I guess my point is, if I can take something with 700hp and go 1.44 60' (on wastegate springs and leaving on all 15psi) at 3600+ lbs then I dont see the gear multiplication hurting as bad as say a nitrous or n/a setup. Yes I'm aware of the physics involved and all that. I swapped to 3.70s and it took a really well prepped track to go 1.37 with more boost, all else basically being equal.

[Phil99vette]

You need to cut 1.20-1.23 60's to run.

[Frank02L]

Yes, there is a big difference in running Outlaw Radial, I understand. Are there turbo cars running 1.20-1.23s on radials? I havent seen any but that doesnt mean they don't exist.

Sorry this is completely off topic.

[CalSpeedPerformance]

Originally Posted by Phil99vette

We're going with a Sonny Bryant crank, 2 custom pieces on the block and a couple other changes to see if we can get it to live @ 2500hp and 8500-9000rpms.

What were the 2 custom pieces and other changes you made?

[Phil99vette]

Originally Posted by Frank02L

Yes, there is a big difference in running Outlaw Radial, I understand. Are there turbo cars running 1.20-1.23s on radials? I havent seen any but that doesnt mean they don't exist.

Sorry this is completely off topic.

I can name at least 10 people that cut 1.20-1.23 60's.

[Frank02L]

Turbo cars you say? Cool I didnt realize they were that quick I thought mid/high 20s was the 'norm' on turbos. Wolfe went 24 the other night when he went 4.70 I think I read.

[Anonymous]

Originally Posted by Phil99vette

So the guys doing the LSx testing saying it will live @ 2000hp but are limiting the testing to 7000 is merely that a test. We're not racing the motors on a dyno. If the LSx was built like a small block chevy or a Big Block chevy we would not have the problems everyone is seeing.

Sorry, but I am a little ignorant in regards to the SBC & BBC.
I only know LSx architecture.

What are the differences you speak of, in reference to the cranks reliability?

[armyspeedfreek]

go with a billet crank