The Rocket, along with the 1949 Cadillac V8, were the first post-war OHV crossflow cylinder head V8 engines produced by General Motors.

The first Oldsmobile V8 was of a flathead design that was developed by Northway Engine Works before GM assumed operations.

The 303-cubic-inch (5.0 L) engine had hydraulic lifters, an oversquare bore:stroke ratio, a counterweighted forged crankshaft, aluminum pistons, floating wristpins, and a dual-plane intake manifold.

Cadillac used a distantly related engine which appeared in three different sizes through to the 1962 model year; though the Oldsmobile and Cadillac motors were not physically related, many lessons learned by one division were incorporated into the other's design, and the result were two engines known for their excellent power-to-weight ratio, fuel economy, and smooth, strong, reliable running.

Instead, influenced by the Space Race between the United States and the USSR, the legendary Rocket was born, available in Oldsmobile's 88, Super 88, and 98 models.

A 1958 2-barrel version produced 265 hp (198 kW) and 390 lb⋅ft (530 N⋅m), but had problems with early camshaft failures due to the high preload valve spring forces.

[citation needed] Applications: Introduced in the middle of the 1957 model year,[6] the 1957 and 1958 J-2 Golden Rocket had three two-barrel (twin choke) carburetors with a vacuum-operated linkage.

Power for the base engine was up to 315 hp (235 kW), even though compression was down a quarter point, to 9.75:1.

From 1961-1963, Oldsmobile manufactured its own version of the Buick-designed, all-aluminum 215 cubic inch (3.5L) V8 engine for the F-85 compact.

[11] The Oldsmobile engine was very similar to the Buick engine, but not identical: it had larger wedge combustion chambers with flat-topped (rather than domed) pistons, six bolts rather than five per cylinder head, and slightly larger intake valves; the valves were actuated by shaft-mounted rocker arms like the Buick and Pontiac versions, but the shafts and rockers were unique to Oldsmobile.

In the mid-1980s, hot rodders discovered the 215 could be stretched to as much as 305 cu in (5 L), using the Buick 300 crankshaft, new cylinder sleeves, and an assortment of non-GM parts.

In development, the high compression ratio combined with the charged load created problems with spark knock on hard throttle applications, which led Olds to develop and utilize a novel water-injection system that sprayed metered amounts of distilled water and methyl alcohol (dubbed "Turbo-Rocket Fluid") into the intake manifold air-stream to cool the intake charge.

If the fluid reservoir was empty, a complex double-float and valve assembly in the Turbo-Rocket Fluid path would set a second butterfly (positioned between the throttle butterfly and the turbocharger) into the closed position, limiting the amount of boost pressure.

The big-block engines initially used a forged crankshaft with a stroke of 3.975" for the 1965-1967 425 and 400 CID versions; starting in 1968, both the 400 cu in (6.6 L) and the 455 cu in (7.5 L) big blocks used a stroke of 4.25 in (108 mm), with crankshaft material changed to cast iron except in a few rare cases.

This very open and flat chamber was fuel efficient and had lower than average emissions output.

The 4-barrel versions had a larger diameter harmonic damper, the 2 barrel only a balancer hub without the rubberized outer ring.

Two distinct versions of the 400 CID engine were made: The 1966-1967 4-4-2 400 cu in (6.6 L) V8 was a short stroke engine which featured B and C cast large-valve cylinder heads and hydraulic lifters of larger diameter, as well as push-rods of different length and diameter than the standard Olds Rocket V8.

A nominal 360 hp was claimed in 1967 when equipped with a W30 camshaft, 4-barrel, and outside air induction, 502 of which were factory produced.

The standard 1965-1967 425 cu in (7.0 L) was called the Super Rocket, and was the most powerful engine option for the Oldsmobile 88 and 98 of 1965-1967.

This engine was only available in the Oldsmobile Starfire, delta 88 and a performance economy model called the Jetstar I.

The "Rocket" name disappeared from the air cleaner decal in 1975, the same year that the catalytic converter was added to the emissions control system.

Additionally, the 403 had windowed main webs, which reduced the internal strength of the block in the crankcase area.

A popular modification made to the 403 to increase power was to swap on early Oldsmobile 350 heads to boost compression.

The 403 Oldsmobile was generally painted "Corporate GM Blue" on every model line it was equipped in.

Applications: A smaller 260.5 cu in (4.3 L; 4,269 cc) V8 was created for the new Oldsmobile Omega in 1975 by decreasing the bore to 3.5 in (89 mm).

The 260 was designed for economy, and was the first engine option above the Chevrolet 250 straight-six, then later the 3.8 L Buick V6, which was standard fitment in many Oldsmobile models by the late 1970s.

The combination of good torque at low engine speeds, the Quadrajet four-barrel carburetor, and the THM-200-4R three-speed plus overdrive automatic transmission having a lockup torque converter allowed for decent performance, and fuel economy considered reasonable for the era, even in the larger and heavier model cars.

In 1985, roller lifters, floating piston wrist pins, and swirl port intake runners were added.

Performance modifications included a "hot" camshaft (in reality, just a camshaft used in various applications during the '70s with .440"/.440" lift and 196°/208° duration at .050"), stiffer valve springs, a larger vibration damper (same as all '73-'79 350s, 403s, and 455s), a Y-pipe dual-outlet exhaust system, and richer secondary metering rods in the carburetor.

Revisions to the engine for 1986 included roller lifters with a slightly smaller camshaft (.435"/.438" lift and 194°/210° duration at .050"), new heads with smaller, swirl-port intake runners, floating piston pins, and larger piston dishes for lower compression (8.0:1 v. 8.4:1).