283 and a Slight Hop Up

[blacknwhitedog]

Comparatively the difference between the old power pack heads and the 305 heads is minimal. Combustion chamber on the 283 is 60cc compared to 58cc on the 305. Intake valve size is 1.72 on the 283 and 1.84 on the 305 heads.

IMHO you won't notice much difference between the two, and if you want it to look "period correct" you'll need to deal with the accessory holes in the front of the new heads. You'll also want to make sure you get don't get the vortec version of the 305's...requires a manifold and valve cover change.

With regard to compression ratio, there is a .2 difference upwards if you use the 305 heads due to the smaller combustion chamber, assuming that matters to you.

if it were me, I'd stick with the 283 heads and use the money you would spend on 305 heads for a set of headers or a new intake etc.