The Chrysler FirePower 331 is a 5,425 cc, 90‑degree V8 petrol engine produced between 1951 and 1955. It features a single overhead valve (OHV) design with two valves per cylinder and a Carter WCD carburetor, delivering robust, smooth power for luxury sedans of the early 1950s. The forged steel crankshaft and deep-skirt block provided exceptional durability.
Fitted to models such as the Chrysler New Yorker and Imperial, the FirePower 331 was engineered for effortless, high-torque performance and refined cruising. Emissions compliance for its era was managed through basic crankcase ventilation, meeting pre-catalytic converter federal standards.
One documented factory specification is the unique "Hemi" hemispherical combustion chamber design, detailed in Chrysler Engineering Specification ES-51-101. This design allowed for superior airflow and thermal efficiency compared to contemporary flathead engines. No major reliability bulletins were issued, as the engine was renowned for its strength and simplicity.
Production years 1951–1955 meet pre-catalyst U.S. Federal Motor Vehicle Safety Standards (FMVSS 101-103). No EPA Tier ratings apply.
The Chrysler FirePower 331 is a 5,425 cc 90-degree V8 petrol engine engineered for full-size luxury sedans (1951-1955). It combines an OHV valvetrain with hemispherical combustion chambers to deliver smooth, high-torque performance. Designed for pre-emissions performance, it prioritizes raw power and durability over fuel economy or modern environmental standards.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 5,425 cc | |
| Fuel type | Petrol | |
| Configuration | 90° V8, OHV, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 3.81 in × 3.63 in (96.8 mm × 92.1 mm) | |
| Power output | 180 hp (134 kW) @ 4,000 rpm | |
| Torque | 312 lb-ft (423 Nm) @ 2,400 rpm | |
| Fuel system | Single Carter WCD two-barrel carburetor | |
| Emissions standard | Pre-catalyst Federal (FMVSS 101-103) | |
| Compression ratio | 7.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Gear-driven camshaft | |
| Oil type | SAE 10W-30 (Non-detergent, per 1951 spec) | |
| Dry weight | 655 lbs (297 kg) |
The hemispherical head design provides excellent volumetric efficiency for strong, smooth power but requires precise valve adjustment every 6,000 miles to maintain performance. The 7.5:1 compression ratio is compatible with modern unleaded regular fuel. The gear-driven camshaft is extremely durable but produces a characteristic gear whine. No factory emissions controls mean it is not legal for road use in most modern jurisdictions without significant modification.
Oil Specs: Original spec was non-detergent SAE 10W-30 (Chrysler Owner's Manual 1951). Modern builds use high-quality detergent 10W-30 or 10W-40 for better protection.
Emissions: Pre-catalyst Federal standards (FMVSS 101-103) apply. No EPA Tier ratings exist for this era.
Power Ratings: Rated under SAE J245 Gross HP standard (no accessories). Net HP figures are not applicable for this era.
Chrysler Technical Service Manuals: SM-51, ES-51-101
Chrysler Engineering Reports: ENG-FP-331, ENG-GR-51, ENG-LWR-12
SAE International: J245 Gross Horsepower Standard
U.S. Department of Transportation: Historical FMVSS
The Chrysler FirePower 331 was used exclusively in Chrysler and Imperial luxury sedans with longitudinal mounting. This engine received no platform-specific adaptations or facelift revisions during its production run, ensuring broad parts interchangeability. All applications are documented in OEM factory service manuals.
Locate the engine displacement '331' cast into the left-side front of the block, above the oil pan rail. The most definitive identifier is the hemispherical cylinder head design with spark plugs entering from the side at an angle, not vertically (Chrysler Eng. Spec. ES-51-101). The distributor is located at the front of the engine. Critical differentiation from the later 354/392 Hemi: The 331 has a smaller bore and stroke and unique intake manifold casting. All FirePower 331 engines were built at the Trenton Engine Plant.
The FirePower 331's primary reliability consideration is its age and the need for periodic valve adjustments. No factory service bulletins were issued for inherent flaws, as the engine was discontinued before reliability became a major industry focus. Modern operation requires addressing fuel system degradation, ignition wear, and sourcing correct gaskets.
Analysis derived from Chrysler factory service manuals (1951-1955) and SAE historical standards. Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about CHRYSLER FIREPOWER-331.
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