Well guys I won a supercharger on Ebay now looking for ways to lowwer compression so I can run more boost. I tring to do this and not sink a lot into it! Whats the thickest head gasket for a 305? My heads have just been redone so I really don't want to swap heads. What do you think of grinding the head chambers slightly bigger or using a ridge reamer to slghtly enlarge cylinders at top? I don't want to mill pistons because they say boost will break ring lands.Any parts that could bring compression down cheaply? Thanks Tim

 

why what compression do you have now?

 

Well I supect it is just under 9:1:1 compression. The heads are small chambered and were surfaced some with valve job. If I could get it closer to 8:5:1 or better yet 8:1:1 I'd be happy. I was thinking of unshrouding the valves to the sides of the head chamber.This would lower compression and help valves too. Anyone know how far you can open head chambers up? Thanks

 

just get a set of dish top forged pistons, that way u lower ur compression but also have some good strong parts in there for the boost

 

Are you sure you want to lower your compression? 305s are suprisingly resistant to detonation under boost... look at willie's setup 15ish psi on 9-9.5 compression...

 

Running thicker head gaskets is the wrong way to go, it will hurt quench and will make the engine more detonation sensitive. Probably the easiest way to do this well is to slap a set of 350 heads with 64cc or larger chambers on it, just make sure they use stock 1.94/1.50” valves so you don’t have clearance problems. While you’re at it, I’d probably use thinner gaskets to get the quench distance into the .040” range (if it’s a stock type build you’ve probably got about .060” or more).

Assuming that you have 58cc heads on it now, going to 64’s will lower compression about .6, if you get rid of about as much quench distance as I mentioned you’ll only lower things about .2-.3. 76cc chambers will lower things about another point.