Reciprocating Engine Overhaul Practice Test

Spalling describes chipping or material loss on a lifter face due to fatigue cracks in the hardened surface being driven to fracture by repeated cam contact. The surface fatigue causes tiny cracks that propagate until pieces of metal break off, forming chips or flakes. This is a specific wear mode tied to brittle fracture of the surface layers under load, and it’s different from other wear or damage modes: pitting is the formation of small pits from corrosion or micro-wear; galling is adhesive transfer and tearing of material between surfaces under high load; and flaking is a more general peeling of surface layers or coatings. Seeing spalling on a lifter face usually signals excessive wear or lubrication issues and often warrants inspecting and potentially replacing the lifter and cam, as well as addressing any break-in or oiling problems.