<VV> Re: ring face materials

[djtcz at comcast.net]

>..........put chrome molly on the top ring, so could be 
awhile before broken in, maybe ............
I think chrome or moly refers to the material that is on the face of the top ring.  It is either one or the other.  It used to be that the moly was sprayed into a channel machined into the ring face, mechanically supporting the moly when sliding, because the moly>iron bond was not strong enough by itself.  Not sure if the plasma moly bond is good enough to survive on its own.
The TRW sales and tech literature of the 70s stated the rails of cast iron on each side of the moly provided nearly immediate ring sealing.
The modern  Sealed Power site recommends chrome faced rings for offroad and dirt applications, and a somewhat rougher cylinder finish.

http://www.21cgt.com/FMWebCatalog/default.htm
http://engineparts.com/p_pistonrings.asp
"Premium ring sets contain either moly-or chrome-faced top compression rings for long life under severe operating conditions. "