LS3 415 Road Race Build
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Teching In
Joined: Dec 2023
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LS3 415 Road Race Build Hi,
I'm starting to research an LS3 build for my 3200 lb stock car used for road racing. I see the CT525 makes ~533 HP and there's a class that runs those motors in 2850 lbs cars. I'll be running alongside that class and want to get my car in the ballpark competitively. So I'm shooting for ~600 HP and plan on doing a 4 inch stroke 415 build. I've done a bunch of SBC builds but this is my first LS.
The use will be road racing, up to 6,800 RPM, about 35 minutes per session, and I intend to get 40 hours out of the motor between rebuilds which seems typical for this sort of race motor.
Some questions...
Thanks!
- Sal
I'm starting to research an LS3 build for my 3200 lb stock car used for road racing. I see the CT525 makes ~533 HP and there's a class that runs those motors in 2850 lbs cars. I'll be running alongside that class and want to get my car in the ballpark competitively. So I'm shooting for ~600 HP and plan on doing a 4 inch stroke 415 build. I've done a bunch of SBC builds but this is my first LS.
The use will be road racing, up to 6,800 RPM, about 35 minutes per session, and I intend to get 40 hours out of the motor between rebuilds which seems typical for this sort of race motor.
Some questions...
- I'm looking at Callies Compstar crank/rods with the ARP2000 rod bolts. Or the Texas Speed TSP stroker kit with their house brand crank/rods and L19 bolts.
- I'm assuming either of these would be appropriate. The CT525 runs stock rods and crank. But since I'm stroking it out to 4 inches, I want the extra headroom.
- I'll be running an external dry sump pump that's run off of a pulley on the front/rear of the damper
- I need the standard "wet sump" crank, right? I'm not running the GM stock dry sump so I don't need the longer snout crank, right?
- Stock main bolts should be sufficient?
- Planning about 11.5 compression and running on 98 or 100 octane. Any concerns there?
- Planning on using aftermarket or ported LS3 823 heads with stock valves, 660 springs, upgraded trunions, stock LS7 lifters. Any concerns there?
- Planning on doing a single plane carburetor intake and Pro Systems carb. A couple reasons why... I've always run carb so it's easy for me. Plus the car is already setup for carb in terms of the air box and stuff under the hood. I know I'll need a timing controller for the coils. Anything else electronic needed to get the motor going? Any gotchas for running a carb on these LS motors?
- I've always locked out my timing on the SBC to 36 degrees or so for race motors. With the electronic timing on these LS motors, is locking out the timing still typical for race applications?
- Where's the point of diminishing returns and/or increased risk with these stroked LS3 blocks (in terms of horsepower, RPM, etc.)?
Thanks!
- Sal
Last edited by ssanto; Feb 12, 2024 at 04:16 PM.
The Craftsman Truck series still all run the LS2 based aluminum 6liter. Ford/dodge/Toyota/Chevy…all run the GM engine. There are quite a few around for sale used. Ive got two of the blocks myself, one I sleeved and it’s in my Chevelle. Both are RYR (Yates) blocks
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Joined: May 2008
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From: Carnation, WA
If you're set on going carbureted, you might consider webers or equivalent. Those will likely run smoother than any other carb you could get across the rev range, and likely make more power as well. Plus, they look cool.
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Thread Starter
Teching In
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I've looked at those spec engines... those make power at higher RPMs and in general you can make power more cheaply/reliably by adding cubes rather than the more expensive valve train investments needed for 7500+ RPM. So since I'm not constrained by needing a spec motor, I've got plenty in flexibility in how to get there.
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I think your right on the money for your build except for the Ls7 lifters. You need some Johnson 2110r lifters if your gonna track this thing and want it to live. The price difference is more than worth running those garbage Ls7 lifters and they wont cost you an engine.
If I were to do it over again id have gone with the small bore ls7 heads from Gwatney Performance vs the Prc 255 ls3 port heads that have currently. The ls7 port flows more and the intake manifolds flow more as well. if you want to stay ls3 port then the Mast black labels seem to be the best. You can make low 600’s to the wheel with a 416 it just depends on how big of a cam you want to run.
If I were to do it over again id have gone with the small bore ls7 heads from Gwatney Performance vs the Prc 255 ls3 port heads that have currently. The ls7 port flows more and the intake manifolds flow more as well. if you want to stay ls3 port then the Mast black labels seem to be the best. You can make low 600’s to the wheel with a 416 it just depends on how big of a cam you want to run.
I've looked at those spec engines... those make power at higher RPMs and in general you can make power more cheaply/reliably by adding cubes rather than the more expensive valve train investments needed for 7500+ RPM. So since I'm not constrained by needing a spec motor, I've got plenty in flexibility in how to get there.
The spec engine has stock rockers and off the shelf PSI beehive springs. It’s an incredibly simple and reliable engine.
The truck series along with ARCA is using the Illmor spec LS engine. It’s a little different. Iron block, more cubes, and EFI. The Yates aluminum LS2 engine is used in the Modified Tour and the Canadian series. I’m a big fan of the RYR engine.
The truck series along with ARCA is using the Illmor spec LS engine. It’s a little different. Iron block, more cubes, and EFI. The Yates aluminum LS2 engine is used in the Modified Tour and the Canadian series. I’m a big fan of the RYR engine.
On an 11:1 416 with completely stock LS3 heads and LS3 intake with crappy mid length headers and crush bent exhaust 2.5" thru a T56 and 335/30/18 out back we made 560rwhp. It ran a BTR Stg3 cam... whatever they had advertised to make 550rwhp. Could've been a Stage4. Your power goals should be pretty easy. I would run more than 12:1 compression as 93 octane will support that. On the same above mentioned engine the customer had the heads ported, the intake ported/rod modded, further custom cam, lots of tuning and it made just under 600rwhp on 91 octane.
This was in an AutoX 1970 C10 truck with 335's square and he drives it like a maniac at redline a ton. Lasted 2 years of very very hard driving before a refresh. He did a ton of Optima events with it also. A few thousand miles easily of punishment. Wet sump oiling with baffle and Accusump as backup. RPMs under 7000. He only pulled it to give it a health check and will rebuild it and opted for even more cubic inches so he bought another motor.
This was in an AutoX 1970 C10 truck with 335's square and he drives it like a maniac at redline a ton. Lasted 2 years of very very hard driving before a refresh. He did a ton of Optima events with it also. A few thousand miles easily of punishment. Wet sump oiling with baffle and Accusump as backup. RPMs under 7000. He only pulled it to give it a health check and will rebuild it and opted for even more cubic inches so he bought another motor.
Last edited by gnx7; Feb 14, 2024 at 12:59 PM.
