Hello , after several super charger projects I tried NA tuning for the LS engines. Target was a 7200 rpm engine with 600HP at the crank. I took a LS 2 block with LS3 heads, a Texas peed stage 3 cam with double chain cam gear at OEM cam timing and a 405ci stroker kit with all the necessary modifications for the valve train. The corvette is equipped with Vararam and long tube headers, empty catalytic converter and 2,5inch exhaust pipes. The car is only making 540HP @ 5700 rpm at the crank and already high torque in the middle power band.
The corvette accelerates from 2500 to 5000rpm better like with 8psi Vortech V2 SC before. I can rev to 7000 rpm, but nor power gain. I did not bother because the car is fun to drive.

Now , I made another cam project for a standard LS3 376ci with a Texas speed stage 1 cam and OEM cam gear. This corvette is also equipped with Vararam and long tube header , catalytic converter but with 3 inch exhaust pipes. This corvette is making 550HP @ 6300 rpm at
the crank. Now I am sure that there must be a restriction in my first project. Except from the stage 3 cam and the 405ci stroker the only difference is the double chain cam gear, empty catalytic converter and the 2,5inch exhaust pipes.
Where should I look at first or are there any other restrictions possible. How much HP at the crank should I expect from LS 2 block with LS3 heads and Texas speed stage 3 cam ?

Any help would be appreciated, thank you.

 

imo that 2.5" exhaust is chocking it up. what intake manifold are you using ?

 

What are your cam specs, not just the 'stage 3' part.. I see they have a stage 3 LS3 cam that's 231/247.. that would be small for a stroker that you are trying to rev out to 7200. I am running a 403" LS2 in my Corvette, and I'm running a 239/247, and that is pretty mild in many people books (its a street car, didn't want stupid amounts of chop/surging).

If the exhaust components you have are good (good quality headers, and the gutted cats aren't a restriction, and the pipe layout is good), then the 2.5" is probably costing you in the range of 15-20 hp. Not enough to only make that much at the crank. LS3 heads and pretty much any LS3 intake normally should support 600-650 crank hp.

Got a dyno plot?

 

Definitely need to know actually cam specs. My 403 LS2 made peak power at 6650 with a 243/249 114+3 cam.

 

It has a stage 3 LS3 cam with 231/247. And an OEM LS3 intake manifold.

Enclosed a calculated dynochart from G-forces. Not corrected , but OK for comparison

 

I have an adjustable double chain cam gear. Running at 0. Could it be that this timing is not exactly the same to OEM timing. What cam timing is to recommend for my combo.

 

I Believe the guys are referring to the exact specs of the cam. my little 227/234 .600 .600 111lsa peaked about 6500 in a ls2 with cathedral heads and fast 92. so it is odd yours is peaking at 5700.

 

Graph is choppy AF. What is your valvetrain setup. Springs, lifters, pushrods, etc

 

OP- when giving cam specs, always give duration, lift, and LSA. Then we have a fuller picture. "Stage 3" means zilch.
Every cam grinder and his cousin has a Stage 3, and they are all over the map spec wise.

 

Texas speed Stage 3 cam : 231/246 .640"/615" 111 LSA, 109 ICL,
Texas Speed & Performance 1.72:1 Ratio LS3 Steel Roller Rocker
TSP .660" spring kit,
GM/Delphi LS7 style replacement stock lifters,
Texas Speed 5/16" Chrome-moly Pushrods

 

I've seen dyno plots of ~224s in 408s that peak at 5700. Thats weirdly early for a 231, and its dropping off, where I'd expect the 247 duration to carry flatter past the power peak. So even if there are things restricting the system, I

Either its not the cam you think it is, or something else is wrong in the valvetrain. Assuming you've checked the fuel system is OK.

 

What are you using for a fuel pump? The car was probably not initially designed for that much power as it relates to the fuel system.

 

Interesting. I'm also experiencing an early peak hp. I have a 404 stroker 11.4 compression with stock ls3 heads, stock lightly ported ls3 intake, 92mm tb, volant intake, 1-7/8 long tubes, 3" dual exhaust, no cats, Texas speed stage 3 ls7 cam- 240/252 .620/ 618 w/ 1.7 rockers 111+2 lsa, .660 dual valve springs, single chain. I also expected hp to carry out farther and also wonder why it didn't. My tuner said it could be the intake. I don't mean to hijack the thread...

 

Odd you both have a LS3 intake and both are nosing over about the same spot. Seems like something in his valvetrain is unstable to have a crazy graph like that.

 

What would be expected for stock heads / stock intake with just a cam and springs? 500 or ish right?

 

Hi firechicken, your 500HP are WHP ore HP at the Engine

 

Cam is advanced about 4-6 degrees too early on the IVC event to peak any higher with a 4" stroke engine. Your IVC is 44.5*.

I made 511/509 on a hub dyno with my 402 running stock ls3 heads, rod mod ls3 intake, 1 7/8 headers and dual 2.5" exhaust. 226/242 on 117+3.5 cam. IVC was 46.5*. It peaked first at 5500, dropped 12hp to 5900, peaked again at 6300 and then fell off above there. You can either enjoy your torque monster, or you can do a cam swap and you'll also need to do either something like a fast 102, or at least a rod mod intake. Stock LS3 throttle bodies are too small for a 402 and I attribute my weird harmonic in my power curve to MAP restriction. It definitely was not a valvetrain issue for me. I would see heavy restriction on the MAP sensor all through the powerband, and would have that flutter/dip at the top end both on the MAP sensor and on the dyno. With a reasonable size cam you should be able to get it to peak at 6200+ and make 600-620hp flywheel. For what its worth, a SBE ls3 will make the same power at a higher RPM, but you'll be up in torque everywhere with the stroker, and in real life driving have better throttle response and midrange power.

I put a much larger 242/250 on 114+4 cam in it (51* IVC) and never dyno'd it again, but rev limiter was set out to 7600 and would pull like a **** to 7300-7400. With a 105mm TB on the ls3 intake it resolved the MAP restriction even though I didn't enlarge the throat of the intake.

This was out to 72-7300 on the 2-3 and 3-4. This was my first test drive it wasn't stalling I got it running quite a bit harder after this. I just put it on flex fuel and the mfer was making at least 540 at the tire with the big cam weighing 2800 pounds with 3.90 gears driving on road race slicks. It actually started to get my adrenaline flowing...then I blew it up XD

 

WHP, that graph is from a dyno dynamics dyno

 

Your overlap is 17* with your 231/247 on 111+2 cam.

I'd suggest something like a 239/251 on 115+3 for cam with similar aggressiveness and driveability but a TON more top end. This is a 51.5 IVC event.

For a bit of an in between, a lot better idle/driving manners but a better power curve with some top end breath you could do something like a 236/248 115+3. IVC of 50* and 12* overlap.

You'll lose some low end torque, but the top end gains will be massive.

The 242/250 on 114+4 cam was a little big for me with 18* overlap, but I had a carbon clutch, 105mm tb, and 2800 pound car. Idle and low speed was a challenge, although I'm sure I could've gotten it eventually.

 

The ls3 intake is a fine piece but runs out of air and peaks early on a stroker. I ran one on my old 421 and had the same problem you're having and only ran 10.80's. The next week I switched to a fast 102 with mid runners and went 10.50's. Eventually I switched to a bigger cam and a LOD intake and went 10.20's.