Resurfacing

A precision machine process in which the cylinder head has a thin layer of metal machined off
the surface.
Cylinder heads are designed to have a small extra layer of metal, often called ‘resurfacing
allowance.’ It is an intentional few thousandths of an inch of extra metal on sealing surfaces
since manufacturers are aware that engines can overheat, gaskets can fail, heads may warp over
time, and repair may require machining. Oftentimes, the head allows for at least once, or often
multiple times, to be resurfaced.
The process helps make the head perfectly flat, smooth enough for the head gasket, and free of
warping, damage, or corrosion.