| Q: Which piston ring goes on top? | 2/26/2025 |
| A: The ring shaped like a keystone or v goes on top. Sometimes there is an o marked on it to indicate which end goes up. You have to be careful, because you might think the ring is too big, if you try to fit it in the slot prior to installation. That is because the slot in the piston is also shaped like a v and putting it in backwards will not tell you if the ring fits or not. | |
Q: What should the piston ring gaps be? | 2/26/2025 |
| A: According to the Cummins Repair Mamual, the top ring gap should be between .40mm and .76mm. The middle ring gap should be between .25mm and .61mm. | |
Q: Why is the middle piston ring marked TOP, when it's the middle piston ring? | 2/26/2025 |
| A: I wonder the same thing. The TOP mark on the middle ring tells you which side is up, as the ring is not congruent like the upper keystone shaped ring. The rings really aren't interchangeable, so most people will generally figure it out on their own. | |