[Jac Mac]

E7 means 1987 or later engine build. Very hard to calculate a comp ratio from compression pressure with so many unknown variables- eg cranking speed-bat cond-lifter leakdown-cold/hot -cam specs. My own experiences with Mercury Marine stern drive units when using 302/351 base was they were around 8.5 to 1 comp ratio. The Prestolites were quite a good dizzy with only mech advance- depending on your location parts could be a problem though.