Piston Ring Install Guide: Clocking and Gap Orientation
How Do Piston Rings Work?
As Total Seal’s Lake Speed Jr. explains in the above video, air, fuel, and spark will make combustion, but it’s not going to make any power without ring seal. Piston rings consist of a top ring, a second ring, and an oil ring, all working together as a team to create the ring seal. This not only seals up the combustion happening above the piston, but also keeps the oil where it belongs in the crankcase.
Each of the three rings serves a different function. The oil ring is handling the bulk of the oil control, scraping the oil off the cylinder wall and feeding it back into the crankcase though drainback holes in the piston. The second ring has a small role in sealing compression, but the main job of the second ring is fine oil control, leaving a thin layer of oil on the cylinder wall to both lubricate and provide the sealing gasket between the cylinder wall and the rings. This leaves the top ring to primarily seal compression.
Do Piston Rings Rotate?
Do piston rings rotate in the cylinder? The short answer is yes, they do. How much will depend on a variety of factors like the amount of crosshatch in the cylinder bore and engine speed. Knowing how to install rings on a piston and how to clock piston rings will allow the rings to rotate without lining up the end gaps and causing excessive blow-by and loss of performance. Starting with the proper ring gap and proper ring gap position on the piston will allow them to rotate while staying in the proper orientation.
Does Piston Ring Orientation Matter?
The ring gap position on the piston is a critical thing to pay attention to when assembling an engine. Properly clocking piston rings when they are installed will keep things running and sealing as they should.
It’s critical that the gap in all three rings does not align to form a clear path between the crank case and the combustion chamber. This will result in blow-by, which has many negative side effects. Many of us have experienced blow-by in worn-out engines, often revealing itself as excess oil coming out of the breather or through the PCV. But blow-by makes more than just a mess on your valve covers. As the critical seal between the piston rings and the cylinder bore is compromised, engine performance will decrease due to the loss of compression. The engine’s oil will have a shorter life and perform poorly as it is diluted by fuel, and the oil that makes it into the combustion chamber will have a lower octane value and can cause detonation.
How to Clock Piston Rings
So now that we know how important it is, just how do you align piston rings? Start by installing the oil ring first, installing the bottom scraper rail, then the expander, and then the top scraper. Once installed, the gaps in the scrapers need to be 180-degrees from each other, with the bottom scraper’s gap on the anti-thrust side and the top scraper’s gap on the thrust side. Which side of the piston is the thrust side? The thrust side of a piston is the side that is being forced against the cylinder wall on the power stroke. On an engine that rotates clockwise, the thrust side is the left side.
With the oil ring done, move on to the second ring. This gap should be 90-degrees from the oil ring scrapers, on the exhaust side. Finally, the top ring needs to be 180-degrees from the second ring, on the intake side. With the rings installed, the piston and rod is ready to be installed in the engine. Speedway Motors has a variety of tools like ring compressors, piston ring filers, and other installation tools to help with this process.
Total Seal's Lake Speed Jr. does a great job of explaining how to stagger piston rings and the proper 4-stroke piston ring orientation in the above video.
