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Old 07-09-2018, 09:02 PM   #13
72K5CSTDarkOlive
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Join Date: Aug 2013
Location: Central Coast, CA
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Re: 427 SBC & 4L80e build

Quote:
Originally Posted by kwmech View Post
An issue I've had with a couple of factory 400 blocks. One block was 30 over and the other was 40. Even after having the block decked and the heads surfaced with compression over 10-1, I've had the head gaskets pop between the cylinders. Removing the cyl head and looking at the block, it looks like somebody took a hacksaw and cut a line down the cylinder walls. So that is why I'm considering the 80 over 350 bore with the 350 gasket. Might give it a bit more meat for sealing between. The 400 gaskets are pretty thin between the cylinders. And with the aluminum heads with the difference in expansion...
The wall thickness with a 4.125 will be over .2500"... The specs on Darts webpage says that minimum thickness at 4.165 is .230" so even at 4.200 you're still at .190" and most OEM blocks are around .120 at .060 overbore. We'll be using a multi layer steel head gasket
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My Build Thread 72 K5 http://67-72chevytrucks.com/vboard/s...d.php?t=628612

Build version 2.0: 72 K5
6.0 LQ9, 4L80e, NP205
http://67-72chevytrucks.com/vboard/s...d.php?t=793192
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1972 CST K5 Blazer Dark Olive
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