Any opinions on Molly rings for a new rebuild of a 292 .thanks

You will probably get several different opinions on this, but it's been my experience that chrome molly rings take a lot longer to seat properly that cast rings, but new technologies may have changed that.

  Ron Lane,  Meridian, ID

i used them once and they took to long to seat.the cylinder has to be perfect 

I'm confused.. I thought older tech Chrome rings were entirely different  than Molybdenum face rings. Can someone clarify for me? Thanks


Paul

They do take a bit longer to seat but they also are low friction and therefore do not get as hot, have less blow-by and wear very slowly (providing it gets proper engine maintenance). As an occasional driver cast rings may be fine but the CrM will last 100,000+ miles!


1936 Ford 3W Coupe : 56 T-Bird 312, 47 Packard 3 speed, 40 juice brakes.
1968 Merc Cyclone FB GT 390, Getting a better front clip!
1977 Ford F-250 Supercab RWD Explorer Long box.
1976 Chev Camaro RS LT
Future rebuild : 1949 Ford F-1

Molly rings are not the same as chrome rings, Molly rings are good, I like to run 2 Molly (both rings are Molly faced), cast is just junk, unless you like doing the job over in about 50,000 miles

My preference for a ring package for a street engine is for a moly filled top ring and a cast iron second ring.  I’m not a fan of the chrome rings simply due to them being finicky to seat in.  The Moly rings are much more heat tolerant than the cast iron rings which is why I like them for the top ring groove.  For the second groove I have good luck using a tapered face cast iron ring.  The second ring is more for oil control than compression seal and having a tapered face creates a wiping action which is better for oil control.

Lorena, Texas (South of Waco)

Ted, do you have any advice on ring gap? I find this kind of thing interesting. There is a debate with some on whether the top ring should have a slightly tighter gap than the 2nd ring or, the reverse also has its enthusiasts. There are arguments for both, apparently.

Always use the manufacturers’ recommendations for ring end gaps before experimenting.  As a general rule for stock width rings, I’ll lean towards 0.004” per inch of bore for the top ring.  Older conventional thinking has the second ring end gaps at 0.003” per inch of bore but this thought process has changed in the last twenty years to having the same end gaps as the top ring and in some instances, more.  If there is an expansion groove or a large distance between the top and second ring grooves in the piston, then the second ring gaps being larger than the top ring gaps is not as critical unless it is a high performance application.  In those high performance instances, you’ll want a larger second ring end gap to prevent any unseating of the top compression ring in the event of a pressure build up between the rings.  If the top and second ring grooves are close together and/or there is a very small or no expansion groove present, then it is typically advantageous to have a ‘generous’ second ring end gap regardless of the end use to prevent the aforementioned pressure build ups between the top two rings unseating and thus breaking the ring seal to the cylinder.

Where metric rings are being used and these being much narrower in width than the stock 5/64” or 3/32” width rings, then the top ring gap for a street engine is typically 0.0045” per inch of bore.  The thinner rings typically have a higher expansion rate than the thicker rings.  Second ring end gaps are the same or opened up to 0.005” per inch of bore depending upon the application.

Lorena, Texas (South of Waco)