This 1/4 scale Offenhauser 270 4-cylinder racing engine was built by Jack Randall using plans by Ron Colonna. Mr. Colonna, who was recognized as the 2008 Craftsman of the Year, has written an entire book of plans and instructions for making the 1/4 scale Offy 270 engine. The full-size Offy engine gained fame in the US oval track racing circuits in the early days due to its power and reliability.
Part of that reliability is due to the fact that the design uses a one-piece engine block and head. This makes it extremely strong, and there is no possibility of a head gasket leak. However, making this possible required some very fancy work deep inside the block and head to machine the valve openings. On a model of size, that work would be virtually impossible, so Ron redesigned the engine in upper and lower halves. However, the joint between the two valves is almost impossible to see, and with the stresses on a small engine being much less, its strength was never in question.
Jack Randall bead blasted some of the parts on his scale model Offy engine to make them look like castings, but in reality no castings were used. Each part was machined from solid aluminum or steel. The engine uses a “dry sump” oiling system where the oil is pumped from a tank below the engine and fed to lubrication points under pressure. The oil migrates back down into the crankcase where it is picked up and pumped back through the tank. This reduces the possibility of oil starvation during hard cornering or acceleration where the oil might be displaced away from the pump pickup in a conventional engine. It also allows for a larger volume of oil to be used to both cool and lubricate the engine.
Length: 11 inches
Height: 7 inches
Stroke: 1.094 inches
Displacement: 60cc (3.66 cubic inches)
Compression Ratio: 9.5:1
Ignition: Solid state spark ignition with Hall Effect dual magnets.