We should start a thread about all the shade tree stuff we have done in the past but don't recommend. I've used a die grinder to knock down the pop up on the valve relief side of some 340 pistons and used a file to flatten it. We were about 300 miles from a machine shop and had to get the thing running and we needed a minimum of .028 p/h clearance. It was only .024
Thing is the engine wouldn't care if the top of the piston had little dips in it or not it wouldn't cause it to explode like using a drill press to bore and hone your engine, having all the cylinders leaning different directions. Or we can start a thread called 'it'll still run'.
When I was a kid and putting junk together sandpapering journals and cleaning off rust pocks and stuff with a file. Crank journals they can be out around a little bit and still continue on no problem only under some extreme usage would they show their ugly faces and fail. You can put a scratch in a cylinder wall can gouge that ****** .030 if you wanted to and as long as you deburr that scratch, the ring skates right over it and it's equivalent of a ring Gap and you would never know it's there...'talking about a scratch, not a circular trench' . Lapped in valves, worn guides...seals will help limp them along to a point even..though the vj will wear quicker...but out of round cylinders,they do not seal.. and when the Rings don't seal ..you can't squeeze anything and when there's no squeeze/compression... that's like an old man's failed heart.... cannot pump the blood to move the body... its done.
Proper Oiling,Ring seal, valve seal, airflow.
If any one of those is crippled or missing... it's over. Starting that way is like still birth.