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**kwmech** · 07-08-2018, 04:41 PM

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...

07-08-2018, 04:41 PM	#9
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,387	Re: 427 SBC & 4L80e build 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...