Home › Forum › Ask A Member › 1957 Mercury Mark 75…..To bore, or not to bore? › Reply To: 1957 Mercury Mark 75…..To bore, or not to bore?
You are well within spec for standard bore for a Mark 75 unless there are terrible scratches/what not in the bores. Block finish hone for a standard Mark 75 is 2.442, from your numbers your right there. This is a service motor Dock Buster I am assuming. My suggestion hone out the 2 cylinders in question and see where your at I would stick with the standard bore even if your a little over this is a service motor. FYI to go the next step .015 over yes you need pistons and rings to match then Block Finish hone for .015 over is 2.457.
Thank you. I guess my biggest concern was the skirt clearance. I can’t find any specs on what that should be. The manual says i have up to .006″ for wear (oversize or out of round) on the bores themselves, but, as it sits, i have anywhere from .006″-.01″ skirt clearance with the old pistons even though the bores are decent. No major scuffing/scratches on either the skirts or bores. Is this still kosher to run with?