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question about milling cylinder heads

3712 Views 3 Replies 2 Participants Last post by  dana44
I am eventually planning on milling the heads on my 400 big block, and I am considering having them milled a little at that time to bring my compression up. The combo is a '77 block, .030" over, with Keith Black 240-.030 flat tops. They sit ~.025 below deck and give 9.0:1 compression with a .020 gasket, or 8.7 with a .040 gasket. My heads are rebuilt iron 452s. Reducing the combustion chamber volume to 78 cc would get me to 9.8:1 with .020 gaskets, and would require milling maybe .040" off the heads. .060" would get me to about 10.2:1 or so.

My question is this: how much can I mill them without requiring custom length pushrods or adjustable rocker arms?
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Although not a big fan of shaving heads, you can get or even make metal curved shims the same amount you shave the heads. Take .040 off and put .040 thick shims under the pedistals to move the rocker arms back to the proper height. I think Mopar Performance themselves offer them, or at least did. One thing to worry about is the pedistal that has the oil gallery in it, make sure the hole is large enough to prevent it from being blocked off.

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Discussion Starter · #3 ·
Awesome. I did not know there was such a thing, but that makes my life a lot easier. It looks like they come in .010", .015", or .030" thickness, so to get .040 I would have to get a set of .010s and .030s, at like $14 per kit. Not bad.

If I would have known what I know now when i originally built this engine, I would have just milled the block .025 for zero deck clearance and 9.5:1 at the time. Oh, well; we live and learn.
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