Cast vs Moly Rings

moper said
Yup.
"Moly" rings are iron rings, with a molybdenum coating applied to the wear surface that contacts the cylinder wall. It's only the top ring that gets it, because that's the one that is designed to seal compression. Moly faced rings need a smoother wall finish than iron faced. Much smoother to really do what they are supposed to, which is seat immediately. Moly does nothing else but seat much faster with the right wall finish.

You beat me to it.... moly rings are just a iron ring with a different facing. But I have used them for years to get the benefit of a faster seal. My engines are all street or rally use engines.

Any shop should be able to finish to either type. BTW, Hastings makes very little differentiation in grit fibish between moly faced and plain iron rings. Untitled Document