Cadillac · Early OHV Cadillac V8
Cadillac 365 V8
The 4.00-inch-bore evolution of Cadillac's early OHV V8 and the engine behind late-1950s Eldorado performance.
365
Cubic inches
Cadillac retained the 331's stroke but increased bore to four inches, creating 365 cubic inches and giving Eldorado models factory dual-quad performance during the horsepower race.
Displacement
365 ci
Bore
4"
Stroke
3.625"
Years
1956–1958
Key Takeaway
The 365 retained the 331's 3.625-inch stroke but increased bore to 4.00 inches. Higher compression and four-barrel or dual-four-barrel induction let Cadillac push output much higher without changing the basic first-generation OHV architecture.
Technical Specifications
- Compression
- 9.75:1 in documented 1956 specification
- Horsepower
- 285 hp standard in 1956; 305 hp dual-quad Eldorado in documented 1956 form; later output varied
- Torque
- 400 lb-ft @ 2800 rpm in 1956 285 hp Cadillac 365 specification
- Architecture
- 90-degree OHV V8
- Block
- Cast iron
- Cylinder heads
- Cast iron
- Valvetrain
- Pushrod OHV with hydraulic lifters
- Aspiration
- Naturally aspirated
- Fuel delivery
- Four-barrel carburetion; dual four-barrels on selected Eldorado versions
The 365 retained the 331's 3.625-inch stroke but increased bore to 4.00 inches. Higher compression and four-barrel or dual-four-barrel induction let Cadillac push output much higher without changing the basic first-generation OHV architecture.
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
- Large 4.00-inch bore
- Strong torque and luxury-car performance
- Factory dual-quad heritage
Weaknesses / Watch-outs
- Original dual-quad hardware is rare
- High-compression restorations require modern-fuel planning
Common Upgrades
- Dual-quad restoration
- Modern ignition
- Cooling-system improvements
Racing History & Legacy
The 365 was the immediate bridge between the original 331 and the 390 that followed.
References & Image Credit
Engine image: Vic Brincat · CC BY 2.0 · source
Engineering Notes Worth Knowing
365 cu in / 6.0 L with 4.00 x 3.625-inch bore and stroke.
90-degree OHV V8 with hydraulic lifters.
1956 factory output reached 285 hp standard and 305 hp in dual-quad Eldorado form.
Used across mainstream Cadillac and Eldorado models.
History · context · related reading
The Story Behind Cadillac 365 V8
The 365 arrived as Cadillac joined the 1950s horsepower race. The bigger bore and available dual-quad induction gave the Eldorado genuine performance credentials without sacrificing the smoothness expected from the brand.
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