LSxFTMFW

Hey guys. So this spring we put a 231/235 .617 .620 112+4 (with PRC 650 duals, TSP pushrods and retainers) in the car with longtubes, X, Vararam and a tune. So we threw it on the dyno yesterday and it made good power considering it was real hot, but am wondering how high you guys spin your cars up? We set my cars limiter to 6800 thinking that would be good enough with stock heads and intake but the graph below looks like we could go up to 7K? What do you guys think?

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tlove32

I have that same cam, on a 117LSA. I run mine to 6800 - really no need to run it higher since the hp peaks in the 6300-6400 range.

zeevette

I agree with t. Your curve is unusual, in the drop off @5k or so. It should be almost flat, and peaking toward the 6500 range. I've never dynoed on an exceptionally hot day, so that may be a factor. There's something wrong with your dyno printout. The numbers don't match the graph, on either HP/TQ.

skyavonee

I think you mixed up the power and torque curves. It's confusing because they use different axes. Power goes 0-450, but torque goes 0-400.

skyavonee

There's probably no harm in setting it to 7k, if you want the bragging rights. But if you spin it up there often, you're probably asking for a shorter engine life.

There's some good info on LS6 rev limiting in this thread, even though they're talking about stock engines:
corvetteforum.com/autocrossing-and-roadracing/whats-the-safe-rev-limit-stock-ls6-heads.html

zeevette

You're right! Totally reversed the things. OTOH, the OP should keep the limiter where it is. I tried to find one of my old ones, when I was H/C only. I dynoed with headers only/untuned, and it only did 377/373, IIRC.

Paul 75 L82

I'm going to go against my better judgment and post my graph. Lets don't get into the different dyno's or HP numbers vs mods, just just look at the curves. If this goes south I'm deleting the graph.

808EB03Z06

I have considered revving to 7000. but there isn't really any point to the extra 200 rpm if power is dropping off.the only reason i could see it being useful is if you wanted to use all 6800rpm before having to shift, but you would have to decide if it is worth it for you.

LSxFTMFW

thanks for all the input guys! It doesn't look like its falling off yet...its still on the way up. The squiggles are the rev limiter so thats why I'm wondering what everyone else has been running their car up to?

LSxFTMFW

Thanks sky. Great info!

Water_Walker

Mine is set at 7200 and the shift is at 7K. My cam pulls up to 7K

Hanlon's Law

If you want to get all mathematical about it, determine what RPM you drop to when shifting at 6800 vs 7000 and compare the area under the curve. Sometimes it's worth revving a little higher even if it's starting to drop off.

skyavonee

In fact, it's pretty much always best to rev beyond the peak power rpm. Not only is there the average power consideration, but there's also power multiplication via gearing. But engine stability/longevity should also play a role in the decision-making process.

onspeed

I have my limiter set to 6800 so I have a little breathing room for 6500 RPM shift without hitting the limiter. HUD needs more increments IMO.

That said, my injector duty cycle almost maxed at 6800, but I very rarely take it that high.

LSxFTMFW

Thanks for the answers guys! tonight Ill move it to 7200 and shift at 7K Ill be replacing the lifters this winter.

Water_Walker

Exactly what I did, but that was based on the cam I have and where the power was.

The Highlander

Tune needs fine tuning... a little lean.... unless it was taken at the tailpipe... if it was at the tail... needs to be retuned.

For what its worth....

With a similar cam I revved my engine to 7250.

Supercharged111

I'm not understanding all these anti-7000 RPM people. If you don't want to rev your car that high, then don't install a cam that wants to rev that high then hold it back because you're not man enough for it. It's asinine.

PRE-Z06

I agree as long as you have good springs that control the valves I'd spin a big cam that peaks at 6500rpm to 7k as it will make more average power taking into consideration the rpm drop from shift extension. Here's something a calculator to put that into perspective. Of course the higher you rev the more strain on the rod bolts and the shorter life the bearings will have, but you don't have to do that all the time and why put a cam in there that peaks that high and not take full advantage of it. The length of the intake runners force the peak under 7k for even the biggest cams, so it's not really beneficial to rev above that IMHO as the power is going to be falling off.

02EBzEE

Hey did you guys stick with mobile 1 5w 30 or did yous switch to another oil and weight with the cam upgrades?