brain

A friend of mine recently put a H/C combo on his car and he said it was slower. The heads flow around 300 he said, and the cam specs are 224/230, I don't remember lift, I think it was .591/.581, or in that area, and a 112 LS. He is running stock exhaust manifolds and stock tuning. He says the car should be faster simply cause it has better (bigger) parts. I disagree, saying its the combination that plays the biggest role. I told him I could see the car even being slower with that cam and stock manifolds. Does that sound reasonable? No tuning at all, nothing. I figured he would have seen a bigger power increase if he had just done longtubes and not the H/C. He put the stock cam back in and said its faster than it was when stock. That makes since, simply because of the ported heads. You get more air in up to where the stock cam's lift is, and would get even more with a bigger cam, providing the exhaust can scavenge it all. Am I making sense, or should his car be faster because he simply threw parts at it? I've tried every example I can give him, (motor is and air pump, inhale through a fire hose, exhale through a straw, etc. etc.) and I can't tell if he doesn't understand, or is just hard headed. What do you guys think? Anyone with cam only NO headers Dynos?

MrPDJ

IMHO,
If you are going to do major mods (like a blower, H/C, etc.), then the most important part of the job is tuning. It wouldn't surprise me at all for someone to do a H/C swap and have it make less power because of a poor tune.

Tell your friend to put the new cam back in and have it dyno tuned!

Kreinmc

The car should have gained quite a few hp even without tuning or headers. Ls1's have a good flowing exhaust from the factory and the tuning usually adapts very well. Most guys i see that do H/C on these cars only pick up 10-15hp from a dyno tune.

Dr.Mudge

Tuning Tuning Tuning Tuning Tuning, his timing and AF are both wacked. Carburated or EFI you do NOT do this without tuning if you want real results, or unless you stay with stock heads and a teeny weeny cam.

JimMueller

That's what happened to me back in 1999. Put in CNC heads and a 216/220 cam with the stock tune. Dynoed 305 HP/TQ. Dynoed higher on a Mustang dyno. Later addedd the longtubes and ls6 intake and it woke up really well. Although the first cam was damaged during a hydralock, so it was with a 218/226 cam as well.

Ironically, I just switched from Fastchips tuning to an LS1-Edit tune today. We baselined with the stock program, with the exception of removing some codes, setting tire height, and LTFT's. We forgot to change the rev-limiter (car came with 118MPH limiter, aka 5400RPM) so peaks were 367/369, and the AF was between 11-12 almost the entire pull.

Final pull was 401/383 (scaling=1). The peaks below 5400RPM were 383/381 to compare with the stock timing & AF. Gained about 10 rwhp above 5500RPM and almost 15tq below 3500 vs. the mail-order Fastchips tune. However, the Fastchips tune had a richer AF across the board. I'm sure Ed could have done just as good or better if I had been able to re-visit. Visited once and had bad gas and it was pinging horribly.

Long story short, tuning helps but I wouldn't depend on it making more than a 15rwhp difference on a 346ci heads/cam setup. Did he buy the heads/cam from the same vendor, i.e., were they designed to work together?

brain

Yeah, I understand that tuning isn't the end all be all, gain 100 HP, but what about headers? Wouldn't you say those are absolutely neccessary with a heads/cam car? I've seen gains of 23 rwhp on stock ls1s with longtubes, and lt1s pick up about 30 rwhp. Wouldn't the gains be even more magnified with heads/cam?

JimMueller

Sure it'll help. The headers will help the scavenging of the cylinders. To get the most out of the setup, yes, you should have headers, an LS6 intake, x-pipe...where does it end? When his wallet is empty

I didn't dyno before/after headers, but I dropped almost 4/10ths at the track, which would be ~40hp. The LS6 intake netted me a peak gain of 30hp & 34tq, but the previous dyno didn't have AF capability. It probably was running rich and the intake leaned it out which is the reason for abnormal gains.