I ran into a set of used performer rpm heads with the 84cc chambers. The current heads on my 383 are an early style closed chamber that I measured at 78cc. They have 2.08 1/74 valves with very lite gasket matching. With the steel heads I’m at 10.7:1 and switching to the eddy will drop me to 10:1.

So my question is will the flow of the heads outweigh the loss in compression or should I mill the Eddy’s to get back around 10.5:1