i am buying some gt40 heads and i was thinking are these gunna lower my compression ratio of my stock 289 or are the gunna raise it or are they gunna stay the same and second they will just bolt right on right BTW i have a C code 289 but i got a stealth manifold and a holley 4160 to stick on with these heads

 

they will bolt on, but, do to a larger combustion chaimber, the CR will decrease slightly...I amdrunk, but I think that the C heads have 59cc chaimbers versis 64cc chaimbers for the GT 40 heads

 

well i am not a professional engine builder but i do know that compression = power so i would have to shave them down a tad prolly i wonder how much that cost usually
and what is slightly does anyone know what my new ratio would be or is there a formula that i can do or even better an online calculator

 

compresion ratios are a good thing for power, but so is airflow, if you loose .5 CR for more flow, it is worth it, besides, if you deck the heads, you will not loose that much. a 9:1 engine WILL be very reliable, while a 12:1 would need constant attention. Also, bumping the bore .030" will help out since you will be compressing that much more air

 

so your saying my comp will drop to about 9.1 or was that an example

 

example....stock was 9.3:1...but today you have lower octane gas

 

true but i just wanted to know what me new comp rat would be cause i would like to keep it above 9:1
i just did hte math and if i did it right i think i usede the right values i will drop to 8.12-1