[Trochoidal]

Originally Posted by Kerry

I found number 7 piston with the oil ring stuck to the piston. Number 3 oil ring was slightly sticky. I was able to get the ring unstuck but could find no reason why it was stuck.

What do u guys think I should do?

I’d bet your “sticky” oil rings and those pistons have a clearance issue.

1) The radius in the OD groove is too large and/or the chamfer on the oil ring is too small.

2) The diameter of the OD groove is too large and/or the ID of the oil ring is too small.

3) The OD groove width is too small and/or the oil ring is too thick.

My 40+ years as a machinist says that I’d be checking all of the relevant dimensions and making blueprints of the results. Optical comparator, CMM, OD groove mics, and Johansson (Joh) blocks are minimum to get the dimensions.

Somewhere there’s something that was either engineered wrong or it wasn’t made to the engineering drawing.

The lead time for one offs in our shop is 4-6 weeks. Subcontracted machine shops also have the same lead time.

It’s a long time to wait for shipping and manufacturing. Add your frustration, time and labor into the mix and you have more invested than GPI or Diamond.

I’d present the error to GPI and have them take it all back and give you a refund or replacement parts. Basically a new set of drop-ins and rings that work.

If you learn nothing is dimensionally wrong with the parts you bought, than all of this means nothing.