CMKworm

iTrader: (2)

What is it and how do I know what I have? Just wondering.

Boostaholic

iTrader: (4)

It is the ratio that the a/f mixture is compressed durring the compression stroke, if your piston had 1 inch of clearance when it was at the top, and went down 4 inches to the bottom, then it would compress the mixture at 4:1.

I believe a stock ls1 is 10.5:1, but I'm not sure, you can calculate it if you know your head chamber size, piston to deck clearance, gasket thickness, stroke, bore and if your piston has a dish you would need that information too.

I think I explained that right, if not someone feel free to correct me or add more.

CMKworm

iTrader: (2)

So if the pistons are stock and I have stage 2 heads and a comp 222 cam what would mine be?

itchygomey98

iTrader: (2)

need to know combustion chamber and gaskets used for those heads

Boostaholic

iTrader: (4)

Your cam doesn't play into compression ratio, it only controls valve events.

Like itchygomey98 said, post up what head gaskets you used and what kind of stage 2 heads you have (Chamber volume if you know) and someone can tell you what your compression ratio is.

1999_SS_M6

By the strictest interpretation, that's an incorrect statement. Cam doesn't affect STATIC compression ratio, but cam will affect dynamic compression ratio. Dynamic compression ratio takes into account the engine as a system... this includes valve events, and how they can affect compression ratio. For instance, compression doesn't begin building until both intake and exhaust valves are closed, and the piston begins travelling up the bore. Your camshaft is going to affect how much compression bleeds off while the piston begins its' upward travel with the valves still open.

Solid346

o if i have a 1.299 piston height and a 59cc heads what cr do i have and how big a cam i can use while the piston have -2 cc with the dome shape

itchygomey98

iTrader: (2)

Most of what you guys are wondering has been answered here - https://ls1tech.com/forums/advanced-engineering-tech/111207-ls1-head-combustion-chamber-cc-volume-vs-cr.html

As far as how big of a cam you can use, there is more to consider than just how much total lift and duration the cam has. That is another topic all together. And what 1999_SS_M6 said is correct, what we are talking about here is only static compression ratio.

IMD

iTrader: (10)

some people should be required to take a class before being allowed to modify their cars.

CMKworm

iTrader: (2)

I don't know what mine are.

Full-Force

iTrader: (11)

AMEN!

Full-Force

iTrader: (11)

umm, just for the sake of another .02 i like to describe it as :

the relationship between the combustion chamber at bottom dead center to the combustion chamber at top dead center ... alot of folks think that the combustion chamber is just in the head, but anywhere combustion takes place is the combustion chamber ... example, most stock blocks wont have a zero deck height so the small hole that the piston is in will also be figured in as part of the combustion chamber at TDC

Ben R

Compression can't begin until the intake valve is closed, so cam choice DOES play a factor in DYNAMIC compression ratio, which is far more important than STATIC compression ratio.

jrp

iTrader: (16)

my static compression came out to 12.08 and my DCR to 9.10

jrp

iTrader: (16)

so how do you expect any help

Ben R

Sounds like a nice setup.