thinking about buildin a 406 for my race car and keep my 355 for a back up..

the heads ive gotten are a set of 50cc heads and i was just wondering what the compression ratio would be with flat top pistons.. on a 64cc head it would be a 11.8 CR

 

 

try this out

1cc per .006 milled

or

1.667 cc for every .010 mill

and from a 72cc head to a 64.5 cc head its about a full point in CR
which is about 8 difference

your going 14 difference, that should take you to about 13.8

 

sounds good for me

 

is that the limit on the restrictions for the class you're in - 406 SBC, because most that i know in dirt track racing everybody runs the max allowed on motor specs or are you switching classes