Thread: Deck flatness specification?

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Originally Posted by mr-natural

Thanks DennyW for your quick response. As I mentioned in my post I exceed that .0015" upper limit for out of flatness spec only at the upper front area of #2 cylinder. Do I need a new block, since the existing block has already been milled some years back?

You will need to measure the block deck height (distance from the centerline of the main bearing bore to the flat surface of the block where the heads bolt on). Design deck height of a small block Chevy is 9.025", but I have found them to be off by 0.020" from one end on one side of the block to the other end on the other side of the block. I would never, ever build a motor without decking the block to square it up. Normally, the "stack" of parts that go into the block measure out to 9.000", leaving 0.025" piston deck height above the piston.

So, it depends how much the block has been decked and what the block originally measured when released by the factory. Measure your block.
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