Drilling piston skirts

wonder if those scratches are about the piston cocking in the bore a bit, so the lower edge scrapes off the oil film?
Normal course of events is the oil running off the piston and sleeve. Function of time.... after a week or two, there's no (or very little) oil there. Start it and you get metal to metal until oil once again coats everything.

Remember, on average, 70% of engine wear comes from start up. That's one reason a New York or London cabby will easily run a half million miles or more.... they hardly ever shut off.
 
Normal course of events is the oil running off the piston and sleeve. Function of time.... after a week or two, there's no (or very little) oil there. Start it and you get metal to metal until oil once again coats everything.

Remember, on average, 70% of engine wear comes from start up. That's one reason a New York or London cabby will easily run a half million miles or more.... they hardly ever shut off.
I used to run engines for 8000-12000 hrs to age catalyst.
At 230 or so lbs-ft 2500rpm.
Approx. 100hp.
Do the math on how many miles this was.
Change the 12 qt. oil every 200hrs.
About 40-60 start/stops.

On another test, MHEV's start every 30 seconds for 200hrs and were toast.
Think what start/stop is doing to your cars! Coated main bearings are a band-aid.

Jimbo is not wrong on that statement.
 
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