Oldsmobile · Gen I Rocket V8
Oldsmobile 371 Rocket / J-2
The triple-carb Rocket that took Oldsmobile's factory performance program into the late 1950s.
371
Cubic inches
The J-2 package added three Rochester two-barrels, dual exhaust and higher compression to the 371, creating a factory street-and-race package closely tied to NASCAR and drag racing.
Displacement
371 ci
Bore
4"
Stroke
3.6875"
Years
1957–1958
Key Takeaway
The 371 expanded Oldsmobile's first-generation Rocket V8 to a 4.00-inch bore and 3.6875-inch stroke. In J-2 form, three Rochester two-barrels and higher-performance tuning transformed the big V8 into a factory street-and-race package.
Technical Specifications
- Horsepower
- J-2 rated 300 hp in 1957 and 312 hp in 1958
- Torque
- 415 lb-ft @ 2800 rpm in 1957 J-2 specification; 425 lb-ft @ 3200 rpm in J-2R race specification
- Architecture
- 90-degree OHV V8
- Block
- Cast iron
- Cylinder heads
- Cast iron
- Valvetrain
- Pushrod OHV
- Aspiration
- Naturally aspirated
- Fuel delivery
- Four-barrel or J-2 three two-barrel carburetors
- Main bearings
- 5
The 371 expanded Oldsmobile's first-generation Rocket V8 to a 4.00-inch bore and 3.6875-inch stroke. In J-2 form, three Rochester two-barrels and higher-performance tuning transformed the big V8 into a factory street-and-race package.
Internal Specifications
Variant-specific values are labeled. Engine families that span multiple years or RPOs can have different heads, cams, induction and rotating parts, so the exact code/year always takes priority.
Notable Applications
Strengths
- Factory Tri-Power-style J-2 induction
- Strong NASCAR and drag heritage
- Big torque from the enlarged Gen I Rocket
Weaknesses / Watch-outs
- Original J-2 induction is rare and valuable
- Period high-compression tuning requires careful fuel and ignition setup
Common Upgrades
- J-2 induction restoration
- Improved ignition
- Modern internal fasteners and oiling updates
Racing History & Legacy
Oldsmobile remained a major NASCAR force through the Rocket era; the J-2 was explicitly aimed at stock-car and drag-racing performance.
The 371 J-2 is one of Oldsmobile's earliest true factory performance engines.
References & Image Credit
Engine image: Herranderssvensson · CC BY-SA 3.0 · source
Engineering Notes Worth Knowing
371 cu in / 6.1 L with 4.00 x 3.6875-inch bore and stroke.
90-degree OHV V8 with cast-iron block and heads.
J-2 induction used three two-barrel carburetors.
Factory J-2 ratings reached 300 hp in 1957 and 312 hp in 1958.
History · context · related reading
The Story Behind Oldsmobile 371 Rocket / J-2
The J-2 proved Oldsmobile's performance identity did not end with the early Rocket 88. Triple carburetors, big displacement, and a clear competition connection made the 371 one of Detroit's earliest serious factory performance V8 packages.
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