The engine took its name from founder Fred Offenhauser, who originally partnered in the project with Harry Miller. It was an overhead cam monoblock four-stroke internal combustion 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) racing engine, with variations used in midgets and sprints into the 1960s, with a choice of carburetion or Hilborn fuel injection.
When both Miller and the company to which he had sold much of the equipment and rights went bankrupt in 1933, Offenhauser opened a shop nearby, bought rights to engines, special tooling and drawings at the bankruptcy auction, and together with other former Miller employees — including draftsman Leo Goossen — took over production and further developed the Miller engines into the Offenhauser engines.
In 1946, the name Offenhauser and engine designs were sold to Louis Meyer and Dale Drake, at which time they formally became known as Meyer-Drake engines. The legacy name Offenhauser remained the preferred and most widely-used moniker. Under Meyer and Drake the engine dominated the Indianapolis 500 and midget racing in the United States. In 1965, Meyer was bought out by Drake, his wife Eve, and their son John. From then until Drake's son John sold the shop to Stewart Van Dyne, the Drake family designed and refined the engine. In 1975, a derivative engine called the DGS (Drake-Goossen-Sparks) was introduced, considered the final engine in the original Offy lineage; it saw modest success on the Indy car circuit.
During the war years, the Offenhauser shop began doing machine work for Lockheed in 1940. The last pre-war engine was shipped on 17 July 1941 and the plant began producing hydraulic systems after the Pearl Harbor attack. Leo Goossen became a full-time Offenhauser employee in 1944.
A 251.92 cubic inch (4,128.29 cm3) DOHC naturally-aspirated four-cylinder racing Offy with a 15:1 compression ratio and a 4.28125-by-4.375-inch (108.744 mm x 111.125 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 produced even higher outputs of 3 hp per cubic inch (137 kW/L). The engine's monobloc construction made it immune to head gasket or cylinder stud problems and allowed for higher cylinder pressures, contributing to its reliability.
A more powerful turbocharged version, used in 1968, gave Bobby Unser the win at Indianapolis that year. This engine made 750 hp (560 kW) at 9,500 rpm from a displacement of only 168 cu in (2,750 cc). Outputs over 1,000 bhp (750 kW) could be attained using around 44.3 psi (3.05 bar) of boost pressure. The final 2.65-litre four-cylinder Offy, restricted to 24.6 psi (1.70 bar) boost, produced 770 bhp (570 kW) at 9,000 rpm.
Versions of the engine won the Indianapolis 500 a record 27 times between 1935 and 1976. From 1934 through the 1970s the Offenhauser engine dominated American open-wheel racing. From 1950 through 1960, Offenhauser-powered cars won the Indianapolis 500 and achieved all three podium positions in all eleven years, and won the pole position in 10 of those 11 years. The Indianapolis 500 was also a round of the FIA World Drivers' Championship during that period.
In 1959, Rodger Ward won a Formula Libre race at Lime Rock Park in an Offenhauser-powered midget car, beating expensive sports cars on a road course. On the strength of this performance, the car was entered in the 1959 US Grand Prix at Sebring, where it proved uncompetitive, setting a qualifying time of 3:43.8 against a pole time of 3:00.0 dead.
When Ford entered the scene in 1963, with increased competition and sanctioning body rule changes, the Offy began to lose its domination over Indy car racing, although it remained competitive through the mid-1970s. The engine's final victory came at Trenton in 1978, in 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. Two Vollstedt chassis with Offenhauser engines failed to qualify for the 1983 Indianapolis 500.
Offenhauser produced engine blocks in several sizes, which could be bored or sleeved and mated with crankshafts of various strokes. Standard sizes included:
97 cu in (1.59 L) — for the displacement rule in many midget series
220 cu in (3.6 L) — for AAA (later USAC) sprint cars
270 cu in (4.4 L) — for the Indianapolis 500 under AAA rules
255 cu in (4.18 L) — for Indianapolis (1930s fuel consumption rules)
252 cu in (4.13 L) — for Indianapolis under USAC rules
168 cu in (2.75 L) — for turbocharged engines at Indianapolis to 1968
159 cu in (2.61 L) — for turbocharged engines at Indianapolis from 1969
This article is based solely on the supplied corpus. No external sources were consulted; claims that could not be substantiated against the corpus were omitted under the drop-the-claim rule.
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