10.5 assumed compression ratio might actually be closer to 10 to 1 on a production engine. Pontiacs historically were lower than 10.75 to 1 on their engines.
That being said, a 10 to 1 engine with 30 psi with 11 degrees of timing basically means that the combustion cycle is starting late therefore the cylinder pressure is lower tna it would be at 27 degrees of timing. Your engine was probably not giving up near as much cylinder pressure at 30 psi of boost even with 8.75 to 1 compression ratio. Off boost I bet it drives nice with 10-1 compression ratio even with late timing.
Tom V.
ps don't give up on going with boost on the V-8 engine. Just buy the right CR pistons as adding a thick gasket to lower compression ratio make the engine want to knock much easier.
Tom V.
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"Engineers do stuff for reasons" Tom Vaught
Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.
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