641 Engine Smoke

You could drop in a set of oversized rings and get away with it (fingers crossed). .025 in just shy of 30 over. You'd want find a set of rings that has a solid one piece oil ring (trust me). If you properly gaped them they would do a good enough job to stop smoking and run the machine (for the most part). But it would not be ideal. You would likely have some piston slap (pistons rubbing/banging against cly walls) and may continue to smoke from breather until they get wore in and match up with the out of round issue. Rings alone would be a desperate, got to get it running, real cheap, and fast patch (that I have done before).

Best thing would be a sleeve/piston kit if your just concerned about a little blow by. Because rings alone likely won't have a running tractor running much better in the end. Nor will they solve the real issue (cly wear).

So the answer is, surprisingly, I don"t know.
RAB