mercruiser 140 low compression & cracked exhaust manifold

[Grub54891]

I use a machinist straight edge

yes, that is the best route, but when someone is throwing out a good chunk of steel, it's free and flat. I always check the straightedge for flatness every few uses.

 

[SternDriveEd]

Engine rebuilders use a specialized straightedge. It is as long as the cylinder head. They use a specification to check for total warp from one end to the other end of the head. Then another spec for checking the space in between any cylinder to the next. Same checks are made on the deck surface of the block.

 

[todhunter]

I paid $20 for an aluminum straight edge on Amazon. Dead flat. Just don't drop it or bang it into anything and it works well. Good cheap alternative to a steel straight edge.