What’s the best way to break in a new engine?
This topic is a compilation of several XLFORUM threads on heat cycling:
Manufacturers and Industries alike condone the practice of Heat Cycling as a deterrent against micro-welding. Micro-Welding between rings and pistons are not a myth. 31) It is defined as adherence of sporadic particles of aluminum from the piston to the bottom side of the piston ring by SAE (Society of Automotive Engineers). 32)) Several other things can also cause micro welding, such as improper taper on face of ring, improper ring tension, improper ring material, improper clearance, improper assembly procedures/specs and clearances, improper assembly lube, improper initial tuning, improper initial break in. Too much surface contact between a new ring and perfectly smooth bore can cause excessive friction and heat. 33) piston lands too high on pistons on HP engine, improper clearance between ring and groove in cylinder, or incompatible materials with different coefficient of expansions. Piston and or rings got too hot from lean AF mixtures, timing too advanced, getting them too hot too soon can also cause it. 34) The variables are so vast, even SAE concedes that because of the variables at large in normal settings, it is difficult to find the proof needed to get a better handle on the subject. 35) So, SAE did a lab test and produced micro welding in a six cylinder high output 2 stroke water cooled engine in 30 minutes with silicon aluminum pistons and treated ductile iron rings running at 5,200 RPM and no break in time using an accelerated bench test in 1996. 36) No other evidence of testing for micro welding of rings has been found to be done by SAE. Obviously, proper heat cycling will not prevent micro welded rings when a multitude of other problems exist. 37)