How much compression would I lose going from the 58cc heads I have on my 305 to heads with 64cc?

 

You'd go from 9.5:1 to about 9:1 depending on the thickness of the gasket you use.

 

thanks

 

figured it might be a little more then that

but don't hold me to that I'm just guessing



how come the larger head if you don't mind me asking?

 

the actual loss will be about .7:1 with a direct swap (same gasket compressed thickness, but if he goes with a little thinner gasket it will be around .5:1.
Now if he were to use a .016" shim gasket the loss would only be .1:1 or less

 

ok I was just too lazy to do math :-)


but was just assuming it would be more like 1-1.5 loss

 

Yeah the reason I'm wondering is I'm considering putting vortec heads on my 305tpi. If I only lost about half a point of compression, thats pretty negligable. Now its just $$$...