1935 Senior Eight 320
1935130 hp @ 3200 rpm
Aluminum-head, dual-downdraft senior Packard straight-eight
Packard 320 Senior Straight-Eight enginePhoto: Pseudopanax · Public domain
Packard · Senior Straight-Eight
Packard 320 Senior Straight-Eight
The nine-main-bearing senior Packard eight with a massive five-inch stroke.
320
Cubic inches
The 320 represented Packard's old-school senior engineering: nine main bearings, an enormous five-inch stroke and effortless low-speed torque.
Key variants
All variants1935 Senior Eight 320
Displacement
320 ci
Bore
3.1875"
Stroke
5"
Years
1929–1939 family era; 1935 specification featured here
Key Takeaway
The senior 320 used a dramatic 5.00-inch stroke, nine-main-bearing support, and traditional L-head construction. Its architecture emphasized exceptional smoothness, low-speed pulling power, and durability in Packard’s premium Eight models.
Technical Specifications
- Compression
- 6.5:1 in documented 1935 specification
- Horsepower
- 130 hp in documented 1935 specification
- Torque
- No single verified factory torque figure is retained for the broad 1929–1939 320 family in the current source set
- Architecture
- L-head inline eight
- Block
- Cast iron
- Cylinder heads
- Aluminum in documented 1935 senior specification
- Valvetrain
- Side-valve L-head
- Aspiration
- Naturally aspirated
- Fuel delivery
- Dual-downdraft carburetion in documented 1935 specification
- Firing order
- 1-6-2-5-8-3-7-4
- Main bearings
- 9
The senior 320 used a dramatic 5.00-inch stroke, nine-main-bearing support, and traditional L-head construction. Its architecture emphasized exceptional smoothness, low-speed pulling power, and durability in Packard’s premium Eight models.
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.
Identification & Output
- Engine codes / RPO
- Senior Eight motor-number ranges vary by series; representative 1935 320 motor range 385001–390301
- Casting numbers
- No single universal 320 Senior casting is retained across the 1929–1939 family; identify by motor number, 3.1875 x 5.00-inch bore/stroke, nine-main-bearing architecture and series.
- Power rating
- Period brake horsepower / SAE gross-era rating
- Horsepower RPM
- 130 hp @ 3200 rpm in documented 1935 specification
- Torque RPM
- No verified single torque/RPM figure retained for the full 320 Senior family
Operating Specs
- Production notes
- The senior 320 family used a long 5.00-inch stroke and nine main bearings. For 1935 Packard standardized an aluminum cylinder head, 6.5:1 compression and 130 hp.
Compatibility Notes
- The senior 320 is not interchangeable as a unit with the later junior 282/288/327 engines simply because they are all Packard straight-eights; dimensions, main-bearing architecture and external hardware differ.
- Use motor-number range and exact series when sourcing cylinder heads, carburetors, ignition, clutch and internal parts.
Notable Applications
Packard Eight senior modelsPackard 1200/1201/1202 series
Strengths
- Nine-main-bearing crank support
- Exceptional low-speed smoothness
- Prestige senior Packard heritage
Weaknesses / Watch-outs
- Very long stroke
- Heavy and physically long
- Restoration parts can be specialized
Common Upgrades
- Preservation-oriented rebuild
- Cooling-system restoration
- Period ignition and carburetor service
Racing History & Legacy
The 320 was a senior luxury-car engine, not a factory racing program. Its engineering emphasis was smoothness, long-stroke torque and refinement in Packard’s premium Eight models.
The 320 embodied Packard's traditional senior straight-eight philosophy before the lighter 356 arrived.
References & Image Credit
Engine image: Pseudopanax · Public domain · source
Packard Club 1935 Eight reference data
club reference
Classic Car Database 1935 Packard Eight specs
technical reference
Packard straight-eight firing-order reference
technical reference
1935 Packard Eight 320 specifications
historical specification
Packard Club — year/model/motor-number identification reference
club identification reference
Key Factory / Build Variants
Engineering Notes Worth Knowing
01
3.1875 x 5.00-inch bore and stroke; 320 cu in / 5.2 L.
02
Senior L-head straight-eight with nine-main-bearing crank support.
03
Documented 1935 output: 130 hp.
04
Used in senior Packard Eight 1200/1201/1202-series models.
History · context · related reading
The Story Behind Packard 320 Senior Straight-Eight
Before Packard’s later 356, the 320 represented the company’s classic senior-engine philosophy: long stroke, many main bearings, and effortless power delivery for large luxury cars.
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