1971 340 Build - Choosing piston rings dilemma
Are these companies all making their own rings or do they all buy generic rings from a couple of manufacturers and put them in their own box with their own advertising?
Also is "Plasma Moly" and just "Moly" the same thing, or is Plasma Moly better?
Lots of questions (maybe too many for one post!?!), hoping for some guys who have knowledge and had experience with different brands of Moly ring sets for the common KB Hypereutectics.
Thanks.
Most make their own but I’m sure like all things some are re-boxed. In a mild application there’s not much you “need”, aside from buying rings that will work with the cylinder wall finish the shop gave you. A picture of the bore might help eyeball it if you don’t know how they left it.
Cast rings are the basis for all types you might be interested in. The coatings and ring design comprise the price swings.
In order of performance (at least imo)
1. Cast top and standard design 2nd with no coatings
2. Cast top and 2nd with moly coated top ring (2a. Is file to fit rings)
3. Cast top and 2nd with plasma moly coated top (3a is file to fit)
4. Cast top with cast Napier design 2nd, with moly or plasma moly coated top ring (4a is file to fit)
You don’t need gapless, chrome, or any other gimmick.
Assuming the bore are prepped right- the cast top and std design 2nd with a moly coated top would be fine (#2a).
If you’re not sure or the bore is too rough, cast top and cast 2nd with no coating is fine (#1). That’s because if the bore is finished right a moly ring will seat fast. If it’s too rough it will just strip the moly off and then break in like a plain iron ring and you paid for moly for nothing...
Last- on the ring gaps: follow the spec sheet for the top ring especially, and add .004” to the 2nd ring gap. I like file to fit but to be honest you should be giving them bigger than the stock part anyway so you could go non file to fit and be fine.
