hi i had a 91 tpi motor from a z28 put in my 92 2wd chevy truck, the motor is .40 over with flat top hypereutectic pistons, im running the stock cast iron heads, i want to know what my compression is because im looking for some afrs and i would like to have around a 10:1 or so.

 

To many variables that need to be either known or measured.

I'd guess around 9:1 -8.5:1 though.

 

what variables do u need to know, maby i can help or find out? is there anyway i can test my cilinder pres and then figure out the comp.? that may have been a stupid question, but i dont know much about compression and heads. im guessing that since the heads are stock that the gaskets are the stock thikness and deck height is the same and all that,

 

What pistons do you have? What is the deck height? If the engine has been bored .040" over, I doubt you have factory head gaskets.

Can't really turn cylinder PSI into a ratio.

 

The only accurate way to determine the compression ratio of your motor is to remove the cylinder heads and

*measure the piston deck clearance @TDC
*measure or determine the piston dish or valve relief volume.

*measure the cylinder head combustion chamber volume

*Measure or determine the head gasket volume. (crushed)

Then you can input these variables into a online calc like

This One

Anything else is just a guess.
My guess is, it's between 9.3 and 9.8:1