piston ring side-clearance

40,000 mile Commando with what looks like stock big-slot pistons. Ring side clearance ~.007" Wonder if new rings on the pistons would be acceptable. Had some blow-by but not smoking out the exhaust. Not deposit build up in the head on piston tops. No ridge on the jugs tops
Doug

Probably not, The groove will not have warn evenly. It will have a taper. The aluminum piston's groove is what takes the hit as far as wear is concerned. However, automotive machine shops can cut the top groove square again and insert a thin steel spacer, similarly looking like an oil control ring's scraper (but much thinner). The groove cut and the insert used will bring the piston groove back to the specifications required, with the added benefit of that groove never wearing again.

Douglass Harroun said:

40,000 mile Commando with what looks like stock big-slot pistons. Ring side clearance ~.007" Wonder if new rings on the pistons would be acceptable. Had some blow-by but not smoking out the exhaust. Not deposit build up in the head on piston tops. No ridge on the jugs tops
Doug

Click to expand...

Original side clearance was less than .001.

.007 is shot. Jim

Its cheaper and better to renew the piston assemblies. I had a similar problem to you, but no obvious blow by symptoms except heaps of crank case compression pushing oil out everywhere. The engine died one day [ the result of badly worn pistons and rings which had turned into broken top rings and ring lands. ]. I don't recommend machining pistons to square up the ring grooves. So long as the bore wear is well within specs, just fit new pistons. Never hone or even de-glaze the bore. Just remember honing in particular and deglazing just remove precious metal from the bore. Rebuild the engine and ride it hard.

Dereck