Abstract: The disclosed multi-cylinder, poppet-valved engine, has replacement cylinder sleeves larger than the original sleeves, and laterally supported near their upper ends by an aluminum alloy plate having a continuous flange or boss projecting into the cylinder block. The flange has an inner perimeter surface having a profile fittingly engaging upper exterior cylindrical surfaces of the sleeves providing lateral support to the sleeves and heat transfer from the sleeves to coolant and to the block.

Abstract: The disclosed multi-cylinder, poppet-valved engine, has replacement cylinder sleeves larger than the original sleeves, and laterally supported near their upper ends by an aluminum alloy plate having a continuous flange or boss projecting into the cylinder block. The flange has an inner perimeter surface having a profile fittingly engaging upper exterior cylindrical surfaces of the sleeves providing lateral support to the sleeves and heat transfer from the sleeves to coolant and to the block. The flange further provides a coolant groove that circulates coolant around the perimeter of the cylinder sleeves to further the heat transfer from the sleeves to the coolant and to the block. The plate is sealed to the block and head with a spacing and gasketing to accommodate thermal expansion while avoiding combustion gas leakage at the cylinder sleeve tops.