Morris Minor Owners Club

I've got a standard 1098 moggie engine recently removed from the car for upgrading.
I'm assuming has never been rebored, having the engine plate still attached. It ticks over at 40 psi oil pressure and rubs at 60, both when hot. However it's down on compression at 100 psi on all cylinders.
I'm pretty sure the rings got overheated when on a very hot day it dropped loads of coolant which I simply didn't notice at the time. Since then I've done the head gasket and reground the valves ( which were fine) . Still reads 100 across the board.
With engine out now I'm hoping that the bores are within tolerance for re- ringing the standard pistons and honing I'll rebuild with new standard bearings.
Standard 1098 pistons have a diameter of 64.06 mm. I
Have a dial gauge and bore gauge so I'm wondering what the permissable tolerances would be at top middle and bottom of piston travel. Bores are polished but unmarked with no ring at top.
Thank you

Standard bore is 2.542"/64.56mm so that can be measured. From memory I think more than 0.006" is problem territory for piston to bore clearance. And if the bores are oval of course.

Were you getting signs of blow-by?

No signs of blow by as in excessive fumes from breather. When the engine came out the clutch bell housing had an dark oil coating so perhaps from crankshaft seal. Weeping from timing chain cover but that is not uncommon.

It's a matter of how it's worn rather than how much, steps will break rings and ovality will cause blow by. You can usually get by with a bit of taper (set the ring gap at the tightest point), As a rule of thumb if there is no wear step and no scratches there is a good chance it might live again with a hone, but needs measuring to have a better idea.

It's good there's no step and in a while I can come back with the measurements which will give some data re ovality and wear overall.