how much off head
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Senior User
Joined: Jul 2001
Posts: 352
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From: Palatka, FL
how much off head
I am thinking about doing some headwork to my 83 300. I am going to try out the 1.75 ratio chevy rockers on it as well with stock valves. All i want to do to the head is gasket match it and clean up the ports and have the head milled for more compression. What is the maximum I can take off the head and still use the stock valvetrain? What compression will this yield me with stock block and pistons?
Postmaster
Joined: May 2002
Posts: 3,241
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From: Broken Arrow, OK
Milling the head for more compression is a pretty futile exercise. As a general rule, with a 4" bore you remove 1cc of chamber volume for every 0.006" you remove from the head. It takes about 13-15 cc of chamber reduction to increase compression a full point. Even a half point gain would be 0.040-0.050 removed from the head. If you have adjustable valvetrain this shouldn't be an issue. It does reduce the deck thickness of the head and weaken it. There is a point where the engine will start having headgasket problems because of insufficient deck stiffness. Depending on what type of equipment the machine shop has this could also be a pretty costly operation. Another option might be to shop around for a thinner head gasket.
New User
Joined: Feb 2005
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You can go as much as .060 if you like. It will make some difference. You may have to go up on your octane once you do this. Changeing Pistons is the better way. You can also deck your block some and less on the head if you like.
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Enjoy FTE
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Freshman User
Joined: Nov 2001
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From: Phoenix USA
I had .060" removed from my cylinder head, and used .060" undersized pushrods with the stock non-adjustable valve train on my 79. Runs great, no issues except I had to go up to mid-grade (89 Octane) gasoline.
