99CamaroSS_

this may sound retarded, but how do you know what is the correct ratio for your car, and how do you check it?

sorry i dont know much about cars.

Viper

iTrader: (6)

'Correct' is a funny word.

Stock is 10.2:1

Boost needs lower compression, nitrous likes higher, N/A most guys don't go over 11.1:1 due to the gas we can get ( 92-94 octane ).

As far as checking it:

http://www.rbracing-rsr.com/compstaticcalc.html

Cal

iTrader: (1)

Big cams like higher compression because the intake/exhaust overlap bleeds some of it off.

ssheets

iTrader: (1)

tim99ws6

iTrader: (31)

11.12 static here!

madslow

honda guys can run 12.5 compression on 93 octane. if they can do it, why cant we? im sure the ls1 can do 12.5 with proper tuning.

tim99ws6

iTrader: (31)

static, not dynamic. i would imagine their dynamic compression on a 12.5:1 static isn't any higher than what we are running. I know NOTHING about honda motors, so that might just be completely wrong, but that's my first inclination~!

TheMNkid

What kind of horse power would you gain going from 10.2 to 11 by shaving the heads down?

SiL3NtXWS6

iTrader: (17)

you get about ~4% increase in power for every point of compression

99CamaroSS_

how do you go about boosting your compestion ratio up like a point? What do you need to do, or how do you do it?

Blue Falcon

mill your heads, different pistons....

TheMNkid

If I shave the LS1 heads down to get 11:1 compression would I need new pushrods?

SiL3NtXWS6

iTrader: (17)

you are messing with valvetrain geometry.. so yes, you would probly need new pushrods.

MUSTANGEATER

iTrader: (10)

I would advise you to weld the chambers or angle mill the heads. There is no correct compression ratio. If you are going to run 93 octane I'd work on other mods to support a pump gas motor with good compression. The right cam, quench and cooling will allow you to get away with a lot of stuff you don't normally think you can.

TheMNkid

Like what? I have a custom cam from EDC but it wans't built for compression. Mild cam. But it got me thinking about porting my heads and maybe bumping the compression up.

Cal

iTrader: (1)

How often is this done on LSx heads? Seems like an advantage over milling them is you would not loose P2V clearence.

MUSTANGEATER

iTrader: (10)

Just to list a few, Evans coolant, engine coatings, and the proper quench come off the top of my head. The most important part is paying attention to your timing, and Dynamic Compression Ratio

It's not just for piston to valve clearance anymore Think about reshaping the chamber for efficiency and a better flame area.

TheMNkid

I mean what stuff can you get away with? Also, who welds heads? Thnaks Mustangeater!

MUSTANGEATER

iTrader: (10)

Well pertaining to this discussion it would be a Higher Static Compression Ratio on Pump Gas. Any good porter will have a good welder

Cal

iTrader: (1)

Well I have a good welder for welding aluminum, but I'm a pretty shitty porter! However, I'm trying to improve.

What general areas in the combustion chamber would be best for depositing some aditional metal? I assume away from the valves to avoid blocking flow. I need some more compression, but I would rather not mill the heads.