1977 850 piston ring confusion

[mprtech]

Hey guys, I'm in need of standard rings for my 850 overhaul. The problem lies in the fact I have 2 ring Pistons yet all I see listings for is 3 ring sets? Then I get in the keystone versus rectangle cut and I get more confused. What I appear to have is two rectangle cut rings on each piston. Why does every catalog offer a 12 ring set? What rings do I actually need, thanks in advance

 

[Chris1956]

I think the 2 ring pistons are replacements, and have keystone rings. A Merc Dealer should have the correct rings. You will need to determine if they are oversize pistons or standard.

Original pistons would have been 3 rectangular-shaped rings, I would think, in your motor.

 

[mprtech]

Thanks Chris, the rings in question are Sierra, they come in three ring sets. From what I can gather they are the same part number for the inline 6's and that would explain the 12 ring sets offered. So far pleased with the sierra's they all needed .006 trimming to get .018 end gaps, there also stamped VIP which must be the manufacturer.