Offenhauser

Offenhauser was an American engine design that dominated American open wheel racing for more than 50 years and is still popular among vintage sprint and midget car racers.

The Offenhauser engine, familiarly known as the "Offy", was developed by Fred Offenhauser and his employer Harry Arminius Miller, after maintaining and repairing a 1913 Peugeot Grand Prix car of the type which had won the Indianapolis 500. Impressed by the double overhead cam, four-valve-per-cylinder design, which was a great leap forward at the time, they designed an engine on similar principles. Originally, it was sold as a marine engine. In 1930, a four-cylinder 151 cu in (2.47 l) Miller engine installed in a race car set a new international land speed record of 144.895 mph (233.186 km/h). Miller developed this engine into a twin overhead cam, four-cylinder, four-valve-per-cylinder 220 cu in (3.6 l) (3.6 L) racing engine. This would be used in midgets and sprints into the 1960s, with a choice of carburetor or Hilborn fuel injection. When Miller went bankrupt in 1933, Offenhauser bought the shop and the rights to the engine. He and another Miller employee, draftsman Leo Goossen, further developed the Miller into the Offenhauser engine. Then in 1946 the Name and engine designs where sold to Louis Meyer and Dale Drake. Meyer was bought out by Dale, wife Eve and son John in 1965. From then until Dale Drake's son John Drake sold the shop to Stuart Van Dyne, the Drake Family designed and refined the engine until its final race days. It was under Meyer and Drake that the engine dominated the Indy 500 and midget racing in the United States.

One of the keys to the Offenhauser engine's success was power. A 251.92 cubic inch (4,128.29 cm³) twin-cam four-cylinder racing Offy with a 15:1 compression ratio and a 4.28125-by-4.375-inch (108.744 mm × 111.1 mm) bore and stroke, could produce 420 hp (310 kW) at 6,600 rpm (1.77 hp per cubic inch (81 kW/L). Other variants of the engine produced up to 3 hp per cubic inch (137 kW/L). Another reason for the engine's success was reliability; unit construction (no separate cylinder head) meant the engine was not vulnerable to head gasket or cylinder stud problems and allowed for higher cylinder pressures.

From 1934, through the 1970s, the Offenhauser engine dominated American open wheel racing, winning the Indianapolis 500 27 times. By then, the company had already been sold, right after World War II, to Meyer-Drake, who continued to build the engines. From 1950 through 1960, Offenhauser-powered cars won the Indy 500 and achieved all three podium positions, winning the pole position in 10 of the 11 years. In 1959 Lime Rock Park held a famous Formula Libre race, where Rodger Ward shocked the expensive and exotic sports car contingent by beating them on the road course in an Offenhauser powered midget car, which was normally considered competitive for oval tracks only.

When Ford came on to the scene in 1963, the Offy lost its dominion over Indy car racing, although it remained a competitive winner through the mid 1970s even with the advent of turbocharging. Before turbo boost limits, over 1,000 bhp (750 kW) could be attained using around 120 in Hg (44.3 psi (3.05 bar)) boost. The final 2.65-litre 4 cyl Offy, restricted to 80 in Hg (24.6 psi (1.70 bar)) boost pressure, gave 770 bhp (570 kW) at 9,000 rpm. However, the Cosworth DFX soon proved to be unbeatable and the Offy's last victory came at Trenton in 1978, in the hands of Gordon Johncock's Wildcat. The last time an Offy-powered car raced was at Pocono in 1982 for the Domino's Pizza Pocono 500, in an Eagle chassis driven by Jim McElreath, although two Vollstedt chassis with Offenhauser engines failed to qualify for the 1983 Indianapolis 500.