I have a 1966 Dart GT w/ 273 c.i. engine. I am curious if milling the heads say "20,000 th or so will increase my compression ratio and power? Or if the cost will negate the increase in power. I have done this on engines in the past with satisfactory results. Also if I have the heads shaved, what would be the best amount of material to remove without having to worry about valve/ piston contact? Thanks for any help.
.020 won't get you much in compression or power. All it will get you is a intake that doesn't fit properly without machining and pushrods that are too long. Check them for straightness and take off a few thousands to clean them up if they need it.
