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View Full Version : enlarging cumbustion chambers



copo69
01-20-2005, 04:20 PM
is it possiable to take some dart sbc heads pro one,s alum and enlarge the 64cc chamber to say 72cc,s . ? to lower compression a bit.

Tom Welch
01-20-2005, 04:49 PM
dish the pistons, I believe that the heads will perform poorly if the combustion chambers are enlarged. They are shaped specifically to provide proper flame propagation and other stuff like that.

ProdigyCustoms
01-20-2005, 05:12 PM
I agree with Tom about opening the chambers. The easist way will be to contact Cometic and get some thicker gaskets. Depending on you bore and stroke, going up to a .070 or so gasket in place of a standard .037 - ,040 gasket, will drop it the same amount as opening them to 72s, give or take a bit.

yody
01-21-2005, 12:49 PM
i would advise against using a large gasket, that will ruin your quench and be worse than having higher compression, basically the only good choice would be to go with a different piston

442olds
01-22-2005, 10:20 AM
Do the dished pistons. I spent a lot of time enlarging a set of heads and when I was 6 down I noticed a small pin hole in the 5 chamber, went right into the water jacket where the casting core shifted more than in the others. Cost me a set of heads. Sucks too because i had just spent a lot of money on a valve job and stuff. Why I didn't want to look at dished pistons I have no idea. I guess flat tops just looked so nice at the time.

ProdigyCustoms
01-23-2005, 05:08 PM
I assume by the tone of your question you are trying to lower a running combo. If you are building from scratch, dish is by far the way to go. If you have a built motor and are trying to lower for blower or other reason, and do not want to change pistons, the gasket will work, but is not the hot set up.

copo69
01-23-2005, 05:38 PM
well i just said screw it and bought new heads.