I know this is a hot rod car site but .........I have a 1969 327 in my speed boat. I just rebuilt the bottom end of the engine. The person that I got the boat from put 305 heads on the 327. It is supposed to have more compression. I don't know if they work any better or not. I kinda of wished he had left it alone. The engine runs nice and has lots of low end , but when it is wide open I get a bad spark knock. If you back off the throttle just a hair it goes away. The engine is set up with electronic ignition a edelbrock torker 2 intake and a edelbrock performer 600 carb. I just would like someones opinion on the 305 heads and if they would be causing my spark knock. Base timing is at 8 deg btdc and full is supposed to be 32 deg. Thanks