I’m sure you could find a video on YouTube but it will have obvious corrosion
on the cylinder walls that are above the piston( dependent on the stroke). I’d take a trip to a machine shop and ask them questions on checking for flatness. I think you’ll be surprised how flat it really needs to be and a straight edge isn’t going to prove much. Assuming there is a a obvious burn through area on the head gasket
, that area would be my guess if the problem area unless the head
bolts where not torqued properly. Did you check the torque of them prior to disassembly? If the head checks out to be ok then it was either a assembly error or the block is warped and will need to be machined. If this is the case then why? Check your coolant
system. Might be worth contacting the previous builder
just to see what they have to say but don’t use them again. Don’t put it back together without a good idea what caused the issue.