Kurt Crosbie

Which compression ratio is optimal for more power?

In case it matters, I'm taking an LT1 motor and rebuilding...355, 383, or 396. Haven't decided yet.

Kyle@CSS

Any powr adders? Is this going to be drivin every day?

Kurt Crosbie

Yes, it will be a daily driver. Power addrs? I will do what I need to reach around 500hp.

Kurt Crosbie

Yes, it will be a daily driver. Power addrs? I will do what I need to reach around 500hp.

predator

well you dont want high comp with a blower and 11.1 is going to be pushing the realms of pump gas

zjet

a stock lt-1 has 11.1 compression.they run fine on pump gas.

predator

i think you better read again it is more like 10.5

Kurt Crosbie

Well, which is better for making power? A high number (like 11:1) or a low number (like 9:1)

predator

N/a with the right supporting parts cam etc 11.1 and right gas

llafro

Don't just look at the static compression ratio. You have to look at the dynamic compression ratio. That takes into account the valve opening and closing events, so you know what the compression really is. You can safely run more compression with a big cam.

I run shaved heads along with the thinner Impala head gaskets to raise the compression up to 11.8:1. I have a bigger cam (comp XE 230/236), so the dynamic compression ratio is safe. I run it on California MTBE 91 octane with no problem.

zjet

i havent check my z28,put my 94 corvette as 11.1 nevr been touched motor .it maybe the vettes and zs are different.

JoeliusZ28

my manual claims 10.5

amean94ta

yes it might run fine on 91 but only because the computer retards timing automaticaly you would get a big benefit from runing 113 or better

QCKZ28

you shouldnt have to run 100+ octane until its over 12.0-12.5:1.
ive read many posts about this, try doing a search. be surprising what you will learn.
my CR is 11.3:1 and runs fine with 93 octane, i saw no improvement at the track while running 100 octane.

back to the question
1. as a rule n/a more compression=more hp
i dont think i would go higher than 11.5 on pump gas
2. you cant run boost on a high OR motor, s/c or turbo motors like to use a CR around 8 to 9:1
3. N20 (the best power adder IMO) doesnt require a low CR like turbo or superchargers

hope this helps

Got-LT1

I have always seen LT1s on 10.4 to 1 CR, not a big difference but just letting everyone know.

If you are not ruuning a power adder, go 11 to 1, that's what I'll be doing.