Quote Originally Posted by Powerabout View Post
whats the reason not to go with a keystone ring?

I personally do not like keystone rings. After having owned and operated a Marine Sales and Service business for 13 years I saw a lot of broken rings. Most in OMC engines. Why, because they were keystone rings. That is MY LONE opinion. They are as advertised a pressure backed ring, I guess. However think about what happens in a cylinder with ring and cylinder wear. Put to Dixie cups together and then pull apart. How much do you have to pull before you have a lot of clearance.
As that ring and cylinder wear you have a ring that has lost control of groove clearance. Mercurys with a straight cut groove could wear a lot out of cylinder and ring and still be tight in the groove clearance. If the ring is under constant pressure maybe, however once across the exhaust port, that pressure is lost and the ring becomes drag and goes to the top of the groove and then back as the piston changes direction. Again MY OPINION.

The number 2 ring in this reworked piston is a keystone ring, the standard Wiseco production, Mercury ring. Why did I leave the keystone ring in. Three reasons: 1, I set the bore on the engine at 2.867 which tightens the ring in the groove. 2. The engine runs cooler and has better lubricating oil with the caster oil. 3. The engine will not be run the many hours that a family weekend motor that rusts the cylinder walls between weekend runs.

The Dykes ( L ring ) has near zero wall tension and is normally setup with zero end gap. The ring seats so fast that it has its clearance run in. I turned the new ring with an OD of 2.877 and when the ring was complete I parted the ring with a .04 Dremmel cut off wheel. Placed in the cylinder it had zero end clearance. I set them at .003 end gap just to be safe. The wider ring will carry better over the port than the Keystone ring. The anti-rotation pins are 180 degrees apart. I will put the end gap of the Dykes ring on the land between the exhaust ports.