Re: Cylinder and piston wear

Posted by PackardV8 On 2014/10/1 7:49:07

Remove the rings and keep them in the order and position that they were installed. Look for any conspicuous wear or damage to the rings.
Smoking can be due to rings installed upside down and yes, compression rings installed upside down can cause smoking.

The .010" "taper" (actualy what u describe is bellmouthing wear not taper) is not desireable but not severe either. This becomes a personal judgement call based on future expected service demand from the engine.

At this point i would inspect the rest of the engine to determine condition of bearings, crank etc. Somethingg called plastigauge can be used to measure bearing cleaarence.

For light to moderate service demand i would probably not worry about the bellmouth of the cylinder. Check with a REPUTABLE piston ring manufaturere about how much taper or bellmouthing is allowable for rings. I think u will find that up to .017 taper or bellmouthing is max allowed.
The pistons look ok. I'd run them based on the pics. Unless there is other problems not evident in the pics. I've sure ran worse.

The MAJOR issue of any engine overhaul is INSPECTION and analysis of the existing parts.

Let me put it this way:
Short of any conspicuous bore damage for nearly any gasoline engine it is cylinder bore and pistons that one can be rather sloppy with and still produce a good overhaul. It is THE BEARING FIT AND AND CONDITION of BEARINGS and crank that are critical. Valve seating and stem to guide wear can be critical too.

In this particular case it is a prewar engine anyway???? Which makes it little more than a 40K mile or 60K mile at the max service life engine when it was brand new from the factory.