Hi all,

I'm having the hardest time choosing the right combination for my LS3 Corvette. I've got a (vastly) different opinion from every person I seem to talk to. I drive (not trailer) my Corvette to many HPDE events throughout the year. I know someday I"m going to regret it when things let go but I really enjoy driving the car when I do.

However, the car spends it's greatest amount of time on-track running hard at high RPMs (Barber Motorsports, Road Atlanta, Roebling, etc) for extended amounts of time. I'm not a street racer or a drag racer. Peak HP is not my thing, but 'reliable' torque is important.

I'd like to keep the bottom-end stock for now so P:V clearance is an important consideration too.

I've been recommended a 231/236 .644/.613 LSA 113 which doesn't strike me as something I'd want to track. It seems rather intense for a road cam. I think I'd be changing springs 4 times a year.

I've been recommended 235/234 .621/.612 (LXL exhaust lobe) that actually feels pretty good for what I'm thinking about. LSA 113 I understand the LXL lobes are road course friendly.

I've been recommended G6X3 (who knows the grind) but it too 'sounds' radical for a road course from what I read on the forums.

I've been recommended 235/251 .621/.624 LSA 113. That split seems huge...but I'm just learning so what do I know?!

Whatever cam I choose, I'll certainly install BT Platinum springs that match the lift.

I'm also wide open for heads. Texas-Speed, TrickFlow, Mast. I'm leaning to the TSP 255 & the TrickFlow 255 heads. I was reading that the TrickFlow 235's have excellent velocity for the LS3 but as I said, I'm still learning.

It adds up to a lot of money and I sure hate to make a mistake and go too big on the cam and have something that won't last on the road course. Same for the heads...wanting good flow that produces strong torque.

[EDIT:] BTW, I do have Pfadt headers, a Breathless CAI, and a Jerry Onks tune. I run R-compound tires at the track that I trailer behind my car.

I really appreciate your informed opinions (and experience).

Tom

 

Brian Tooley does custom cams also. Contact him.

You should be more concerned about the type of lobes on the cam which are hard on springs.

Run as much compression as your type of fuel allows. e85 does wonders.
My vote is TFS LS3 style heads. You don't have to rev to the moon for it to be fast on the road course.

You will gain the most by having a 2nd set of wheels with some real slicks on them for the track.

 

also try Pat G. or Martin @ Tick stock cubes 4 road racer as stated... compression and a cam that does not rev 2 the moon you TQ to power out a curve

 

What is the average operating range of this engine?

I would also never run a reverse split in a N/A engine, let alone a LS3 headed engine.

15 degree intake to exhaust duration split is nothing out of the norm for a LS3 engine. Most of my LS3 camshafts have 10-20 degrees intake to exhaust duration split. I've tried smaller splits, but prefer the results I've gathered with larger 10-20 degree splits. Airflow in is airflow out.

 

My car spends a lot of time between 4,000 - 6,800 RPM (redline). When my temps get too high I short-shift but while my temps are good I push it pretty hard. Looking to install a Dewitts to help there too.

I've got some recent track video if you want to see how it's spinning:


Again, I appreciate your comments.

Tom

 

You can also adjust for running high temps by making the engine run rich. But that is an old school carb trick.
If you want custom, we have anything you need. And our custom cams are less pricey than alot of off shelf grinds. We have done them in the past 2 months for cam only, Mast LS7 heads, Trick flow cathedral AND ls3 ports, tsp 5.3s and ls6s, and quite a few LS3 headed builds, wcch LS7 headed C6Zs and ls3 top end swaps on trucks as well as remote tuned half of them! All of our customers love them so far!
Let us know if we can help you!

 

It looks to me like you will need the most power possible from 3200-6600rpm. At least from the video.

It doesn't look like you ever got below 3000rpm and if you did, it wasn't purposefully.

Here is what I would recommend based on your modifications currently and that operating range:

225/236 .612/.578 112+4

 

I would actually go a tad larger and use different lobes. The better area the lobe has the more potential you will have. Esp in the mid range.

 

IMO the exhaust port cares much less about area than the intake.

With the cam I have proposed, max lift on the exhaust lobe would not be reached until 116 crank degrees before top dead center. This is 64 degrees after bottom dead center.

At the very least 50%, if not more than 50% of the cylinders contents(spent exhaust gas) are being evacuated before bottom dead center.

That means that 64 crank degrees before max lift on the exhaust lobe is ever even reached more than 50% of the spent exhaust gas residing in the cylinder is gone.

To me that means the exhaust port cares no where near as much about lift as the intake port.

IMO this is due to the immense pressure differential between the spent exhaust gas in the cylinder before the exhaust valve opens versus atmospheric in the exhaust port before the exhaust valve opens.

When you have a pressure differential that large, the high pressure is going to move to the low pressure area all by itself.

My opinion at least. Others have tested lower lift exhaust lobes and found more power there than with higher lift exhaust lobes. I feel this is from deflection of the rocker arm(teeny 8mm bolt) against that immense cylinder pressure with a faster opening lobe. Faster you open it against that pressure the more it will deflect and the more lift you lose at that crucial moment when the exhaust valve opens.

Again, JMO.

Unless you meant more lift on the intake lobe?

 

I would at least want to know what valves you run before picking a cam.

 

Agreed, but I've pretty much cammed every single set of heads available for a LS3. Ranging from stock LS3 valves to L92 solid stem valves to aftermarket hollow stem valves and solid stem valves. Even titanium.

I've found the LSL/Extreme RPM High lift lobe combination to prove extremely reliable and effective in producing power with the LS engine.

That lobe combination has turned 7400rpm with solid stem L92 intake valves with 150psi seat and 390psi open pressure with stock rocker arms.

 

Not wanting to hijack this thread, however.


From your comments I assume that you would recommend a different grind for my street/drag use.
Car is 2001 Holden Monaro with crate LS3 that weighs 3890lbs with auto and 4.1 gears.

231 239 .617" .624" 113

 

Honestly anything in the higher 220 to mid 230 range will get you what you want on the street.
I prefer a different lobe combo onthe road course/sustained rpm combos and have had better results with more lobe area on both over the xrpm lobe. Not just talking from my opinion.

As far as ramp rate/lobe area on the exhaust goes, maybe you should listen to other professionals more on building in more duration after advertised or .006 because they always see better gains. You dont have to have as much lift but there seems to be MANY different schools of thought on that and is likely a subject for another time

 

Can you shoot me an email? I'd prefer to not take this thread any further off track.


I prefer to use the words, "my opinion" as there are many different schools of thought as you said. Instead of possibly coming across as being rude saying this is the only way you can do it.

I can procure data if that is what you prefer that shows the lower lift lobe tested back to back with a higher lift lobe in a LS3 application to make more power everywhere.

Tooley first tested this himself, and after seeing the results I honestly did not believe them or feel them to be 100% correct in every application. After trying it myself I have found it to be true in nearly every application I have ever worked with.

Billy Godbold has also echoed the same thoughts to me many different times.

Possibly share your results with us where you have made more power/had better results over the extreme rpm high lift lobe? I always respect other's opinions and the way that they feel is best as I have learned many things being open minded this way.

That is not what I have seen personally. Again as I said and you said, there are many different schools of thought.

Last thing I will add is that lift can be deceiving. Something CoSpeed mentioned and if I understand him correctly about building duration after .006 or advertised is that he means in terms of slowing the lobe down. You don't have to have low lift just to have a slower ramp rate lobe.

The ERPM lobe does have added duration after .006 and @.006 versus the intake lobe I used(LSL) and other lobes that are commonly used. A HUC lobe would be a good example. It is a slower ramp rate lobe, but it has more lobe lift than the ERPM. I have used it in place of the ERPM lobe when I felt more lobe lift was needed.

In this case I do not feel it is necessary.

 

Would that be in a street/strip engine that sees that RPM momentarily, or an auto cross application that sustains that kind of RPM?

Personally, I'd be hesitant to run that with solid stem valves. I would probably prefer a less aggressive lobe.

 

What about during the overlap period when the exhaust port is tugging on the intake port providing you have a good exhaust system? Is there not a good opportune time to close the exhaust valve so some of the intake charge does not go out the exhaust port and help get maximum cylinder filling? In otherwords you can get over scavanging and under scavanging.

 

There are so many ways to approach this topic and many ways to get a good outcome.
You are talking about scavenging, but dont forget about reversion as well.

 

I used to be afraid of that solid stem valve. The stock rockers mass is what in my opinion allows that intake lobe to still shine in that application where the valve is rather heavy.

I used to always run Huc or lxl intake lobes with that solid stem valve, but I've seen more torque under the curve with the slightly faster lobe in comparison with no loss up top.

I've used the lsl lobe with ls3 valves in sustained rpm applications such as road course or auto x.

What I was going to suggest to the OP with that cam in this application is a set of dual tapered 3/8-5/16 push rods. I've been using them as much as I can lately. The back to back results versus a smaller diameter tube are well worth it.

 

Why not just use an 11/32" PR and have no issues with possible clearance? Price maybe? But manton pushrods are top notch, and what we like to use in all of our big boy builds.

 

I love the Manton stuff!

I would probably defer to trend on these though.

Have you ever had issues with a dual tapered 3/8"-5/16" in a stock passage?

I've wrapped tape around a straight tube 3/8" and put it in a customers ls3 headed engine before and turned the engine over on the stand and the tape was untouched.