M20b25 Scuffing on pistons and cylinder Wall HELP pls

[ForcedFirebird]

i think the old school method to repair that is to knurl the pistons, it will swell them out some and hold a bit extra oil

Very, very old school. Those knurl and ream repairs were a band-aid for vehicles back in the day that didn't go over 60mph (still used on tractors, big equip etc), and there wasn't an interstate system even built. Same process was used on valve guides - lucky to see another 15k miles (remember when 100k miles was "a lot"?). There were other odd methods my grandfathers used, like portable boring bars that could be bolted to an engine, bore/hone on site, then use over sized rings, or replaced one piston - repair one crank journal etc. Things that are OK on a tractor/ship/budget mobile, but not in a performance-oriented vehicle.

[Andre3127]

My opinion is that its probably fine. Definitely want to look into rehoning the bores, either by carefully using a flat stone hone or having a shop do it. Measure the pistons, but if its just scuffed in that area they're likely fine even if they're a few thousandths undersize. I never measured my scuffed pistons when I did my rebuild, and it runs really strong. Scuffed bores are much more of a concern than scuffed piston skirts, since they guide the pistons and seal against the rings.