Engine block spacer plates were designed to reduce stresses on the liner flange, which could cause it to get cracked. The spacer plate is just a few thousands of an inch thinner than the liner flanges, this ensures the correct liner protrusion and guarantees proper head gasket sealing.

A new spacer plate should always be used when overhauling your engine, or whenever the cylinder head is removed. It is an inexpensive assurance that your engine will be sealed properly.