Quote:
Originally Posted by Heard
Thanks for posting this Ron.
I was getting ready to ask questions about this regarding new after-market heads (Offy, Edelbrock, etc.) to verify that these also need to be measured and/or milled.
As I understand what you are saying and what others have posted, I think the answer is yes, regardless of the CR these manufacturers may advertise.
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the squish has nothing to do with actual compression ratio. the idea is to keep the combustion area as small as possible. if the piston to head clearance is large this becomes another portion of the combustion chamber even when the piston is all the way up. think of a smog head when they used dished pistons to get lower compression. the motors pinged and never ran right. all because of a large chamber volume. in a flathead you actually want the combustion chamber to be the transfer area only.