Advice for 402 Road Race Combo
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Teching In
Joined: Jun 2005
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Advice for 402 Road Race Combo Hello,
I'm building up an 402 LS2 stroker for a road race application in a C5 Corvette.
I have a set of AFR 205 heads that were on the old LS1 that is being replaced. I have a set of Kooks 1 3/4 inch headers with their off-road h-pipe and an LS6 intake with a stock TB. I'm debating about upgrading to the FAST 90mm setup.
The goal is to make 500 RWHP with a nice flat torque curve with plenty of low end power.
I would probably be shifting at 6000 RPM most of the time and occasionally rev to 6500 max.
I spoke with AFR and they seemed to think that the 205 heads would still work reasonably well given my desire for low end torque.
I would like some advice on what compression ratio to target for use with 91 octane pump gas.
Also, any thoughts on cam specs would be greatly appreciated. The LS1 motor was using a Texas Speed 226/226 .584 .584 cam which worked fairly well but seemed to have a lot left at 6500, and not enough at 2000. It made 418 RWHP.
Thanks in advance!
Alan
I'm building up an 402 LS2 stroker for a road race application in a C5 Corvette.
I have a set of AFR 205 heads that were on the old LS1 that is being replaced. I have a set of Kooks 1 3/4 inch headers with their off-road h-pipe and an LS6 intake with a stock TB. I'm debating about upgrading to the FAST 90mm setup.
The goal is to make 500 RWHP with a nice flat torque curve with plenty of low end power.
I would probably be shifting at 6000 RPM most of the time and occasionally rev to 6500 max.
I spoke with AFR and they seemed to think that the 205 heads would still work reasonably well given my desire for low end torque.
I would like some advice on what compression ratio to target for use with 91 octane pump gas.
Also, any thoughts on cam specs would be greatly appreciated. The LS1 motor was using a Texas Speed 226/226 .584 .584 cam which worked fairly well but seemed to have a lot left at 6500, and not enough at 2000. It made 418 RWHP.
Thanks in advance!
Alan
I'm gonna try to give you some vague details on my car, as I won't have the final dyno numbers until Wendsday night. I had it on a local dyno just doing some VE tuning, but was told not to trust any numbers (dyno hadn't been calibrated yet).
I have a LS2 402 with ETP 245 59cc heads, and a Comp 242/248 .611"/.615" 114+2 XER cam in the car. LS1speed told me that installed strait up, the cam peaked in horsepower at 6k but stayed pretty flat until almost 7k. I installed the cam another two degrees advanced to get a better DCR. In doing so, I lowered my peak hp to around 57-5800 rpms. I think I made peak torque around 44-4500 rpms, but it is a nice looong flat torque curve.
For a road racing car, I imagine you might want a numerically lower LSA cam, but I thought I'd give you what I have for comparison. It peaks right about where you want to be, and will probably give me a shift range anywhere between 6k and 6500 rpms. I'll put my dyno numbers/sheet in the dyno section Wendsday night or Thursday if you want to look at it.
I have a LS2 402 with ETP 245 59cc heads, and a Comp 242/248 .611"/.615" 114+2 XER cam in the car. LS1speed told me that installed strait up, the cam peaked in horsepower at 6k but stayed pretty flat until almost 7k. I installed the cam another two degrees advanced to get a better DCR. In doing so, I lowered my peak hp to around 57-5800 rpms. I think I made peak torque around 44-4500 rpms, but it is a nice looong flat torque curve.
For a road racing car, I imagine you might want a numerically lower LSA cam, but I thought I'd give you what I have for comparison. It peaks right about where you want to be, and will probably give me a shift range anywhere between 6k and 6500 rpms. I'll put my dyno numbers/sheet in the dyno section Wendsday night or Thursday if you want to look at it.
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From: Rolesville, NC
here is a thread on road race cams
https://ls1tech.com/forums/generation-iii-internal-engine/422520-head-cam-road-racing.html
https://ls1tech.com/forums/generation-iii-internal-engine/422520-head-cam-road-racing.html
I had exactly your goal. Watch carefully your CR and DCR given piston, heads and gaskets. Your heads and headers are not a problem unless you want big hp at higher rpm. The FAST is not a clear choice either in that it is generally a high rpm device with troublesome fit issues. (been there)
I ended up with Mahle -12 pistons, .045 gaskets for a 11.3 CR. Cams are a whole seperate chapter. I gave Brian at Comp a blank slate and he speced a 238-242/605-610/111+2. I worry a bit about valve train with XER lobes.
I have not finished tuning or dynoed yet but, feels good--
I ended up with Mahle -12 pistons, .045 gaskets for a 11.3 CR. Cams are a whole seperate chapter. I gave Brian at Comp a blank slate and he speced a 238-242/605-610/111+2. I worry a bit about valve train with XER lobes.
I have not finished tuning or dynoed yet but, feels good--
Last edited by See5; Jul 18, 2006 at 07:46 AM.
I don't know why you are worried about power at 2K RPM? You won't be below 4K pretty much 95% of the time on the road course.
I'm with a 346ci stock shortblock with Katech rod bolts, AFR 205's milled .024" (62cc), long tubes, LS6 intake, ported TB, underdrive pulley, TSP 233/239 .600" 112LSA cam. I spend 95% of the time from 4K-6800rpm. If I need to pass someone or on a long straightaway I shift at 7100rpm. 20K miles on this combo with zero component failures. 440rwhp/385rwtq
I would go with a bigger cam and more lift than you are choosing. That 402 can swallow a much bigger cam than my little 346 and still be very driveable.
If you want loads of power across the board and not have to rev the **** out of it... a 236/236 114LSA would work and have a nice idle. If you want more mid/top end power (stops you from blowing the tires off in slow speed corner exits) get more duration and a 112LSA or even 110LSA. Idle will be chunky. PM Patrick G or Ed C. They know cams and others do as well. Big duration cams like as high of compression as you can tolerate on the gas you plan to run. You can make 500rwhp with a 402/AFR combo with the right cam choice.
I'm with a 346ci stock shortblock with Katech rod bolts, AFR 205's milled .024" (62cc), long tubes, LS6 intake, ported TB, underdrive pulley, TSP 233/239 .600" 112LSA cam. I spend 95% of the time from 4K-6800rpm. If I need to pass someone or on a long straightaway I shift at 7100rpm. 20K miles on this combo with zero component failures. 440rwhp/385rwtq
I would go with a bigger cam and more lift than you are choosing. That 402 can swallow a much bigger cam than my little 346 and still be very driveable.
If you want loads of power across the board and not have to rev the **** out of it... a 236/236 114LSA would work and have a nice idle. If you want more mid/top end power (stops you from blowing the tires off in slow speed corner exits) get more duration and a 112LSA or even 110LSA. Idle will be chunky. PM Patrick G or Ed C. They know cams and others do as well. Big duration cams like as high of compression as you can tolerate on the gas you plan to run. You can make 500rwhp with a 402/AFR combo with the right cam choice.
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To answer your original qestion, the max compression ratio to run pump gas is around 8.5 dynamic. Static compression ratio means nothing, the DCR tells all when it comes to knock. Calculate your DCR at www.kb-silvolite.com The duration of the cam plays a part in the DCR. More duration lowers your compression.
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Originally Posted by racecar
More duration lowers your compression.
DCR will depend on intake valve closing. You can increase the intake duration by opening the valve earlier.
Here's a nice DCR link ->http://www.empirenet.com/pkelley2/DynamicCR.html
Last edited by Bink; Jul 23, 2006 at 01:21 AM.
For a 402 ci road race car with desire to have peak power by 6000 and the ability to rev to 6500, you'll want your intake valve closing point to occur between 45-46 degrees ABDC at .050" (it would be 40-41 degrees with a 346). You'll also want your dynamic compression to be around 8.5:1. You can accomplish this many different ways: Wide LSA and short duration or narrower LSA and larger duration. Overlap will be the big difference here.
For max area under the curve for this specific road race application, you can go with COMP XE-R lobes:
232/238 .595/.602 110LSA +1
For max area under the curve for this specific road race application, you can go with COMP XE-R lobes:
232/238 .595/.602 110LSA +1
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
