Milling
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 4
From: Delaware
Your stock Compression Ratio is 8.0:1. Your stock heads have 78.4cc combustion chambers. To raise your CR to 9.0:1 you should take enough off the heads to reduce the chamber to about 65cc. This is a reduction of 0.818 cubic inches. Since the chamber is hemispherical and about 4" in diameter, cutting about 0.065" off the surface should do it. With a CR of 9.0;1 you should be OK on most pump fuels. Check with your machinist to determine if it is safe to cut off 0.065".
Laughing Gas
Joined: Nov 2002
Posts: 1,198
Likes: 9
From: Fairmont
Problem with cutting that much off the heads, you may have to mill the intake side of the head and/or the intake. Bolts and port may not line up. Just be prepared. Somtimes it may get bad enough that the front and the rear of the intake contact the block first.
Laughing Gas
Joined: Feb 2003
Posts: 1,234
Likes: 3
From: In the woods of Oregon
Another thing to think about is valvetrain geometry when milling so much off. In effect it makes your pushrods longer when yoy take deck/head surface away, and makes them shorter when you use thick headgaskets or when you double up on em. With the non adj vavletrain you would need shorter pushrods, cause the hydro lifters can only self adjust so far before maxing or in your case botoming out and causeing a valve to stay open. I hope I made sense, and if not there are alot of people on this site who can explain it better than me.Thanx!
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