I've seen dummies pay outrageous prices for a set of heads with those big humps on them, when a set of regular-production 305 heads will make more compression, and horsepower with just a little tweaking! People GIVE me 305 cylinder heads to get rid of them, and I install oversize valves, and do a slight pocket-porting job, and turn out more power on the dyno than the double-hump type.

Another sneaky trick is to use a set of low-compression heads from a 350, with 76CC combustion chambers, and do a .100" angle-mill job, where .100 inch of material is milled from the spark plug side of the head, tapering to nothing at the intake manifold side. The resulting chamber volume is 60 CC, more compression than a double-hump head. Add a 2.02" intake valve, and a 1.6" exhaust, plus pocket porting, and they make more power than the double-hump types. I've confirmed all this with temperature and humidity compensated dyno runs, not guesswork!
Jerry

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