Piston Ring Welding.
Commonly know as micro-welding it is a condition where aluminum from a piston is transferred to the bottom of the compression ring of the piston. The welding usually occurs at the ends of the piston ring gaps and happens during an engine’s break-in process.
The way to detect this problem is that when a compression ring sticks from welding an engines blowby will increase and the power level of the engine is reduced drastically. If you haven’t run into this problem yet then you haven’t built enough Hi-HP engines. It is advisable to start checking the bottom of the compression rings when you tear down an engine.
The cause of piston ring welding is due to softening of the piston material because the engine got to hot, the piston has poor ring groove machining for flatness or finish, or there is the wrong piston ring to piston groove clearance.
You can you avoid piston ring welding by coating the bottom of the compression piston ring and the piston ring land with a phosphate dry lubricant during engine assembly, and by keeping the top piston ring gaps away from the exhaust side of the piston.