BMW automotive engine families listed as M78. Specifications below retain the source's separate family and variant labels.
Family specifications
BMW M78
| Field | Reported value |
|---|
| Production | 1933–1950 |
| Configuration | Straight-six engine |
| Displacement | 1.2 L (1,182 cc) 1.5 L (1,490 cc) 1.9 L (1,911 cc) 2.0 L (1,971 cc) |
| Cylinder bore | 56 mm (2.20 in) 58 mm (2.28 in) 65 mm (2.56 in) 66 mm (2.60 in) |
| Piston stroke | 80 mm (3.15 in) 94 mm (3.70 in) 96 mm (3.78 in) |
| Cylinder block material | Iron |
| Cylinder head material | reverse-flow, iron |
| Valvetrain | OHV |
| Valvetrain drive system | chain |
| Fuel system | 2 × horizontal draught carburettor |
| Fuel type | Petrol |
| Predecessor | None |
| Successor | BMW M337 |
Variant specifications
Models
| Model | Displacement | Power | Year |
|---|
| 303 version | 1,182 cc (72.1 cu in) | 22 kW (30 PS) | 1933-1934 |
| 315 version | 1,490 cc (90.9 cu in) | 25 kW (34 PS) | 1934-1937 |
| 315/1 version | 1,490 cc (90.9 cu in) | 29 kW (40 PS) | 1934-1937 |
| 319 version | 1,911 cc (116.6 cu in) | 33 kW (45 PS) | 1935-1937 |
| 319/1 version | 1,911 cc (116.6 cu in) | 40 kW (55 PS) | 1935-1937 |
| 326 version | 1,971 cc (120.3 cu in) | 37 kW (50 PS) | 1936-1950 |
| 320 version | 1,971 cc (120.3 cu in) | 33 kW (45 PS) | 1937-1938 |
| 327 version | 1,971 cc (120.3 cu in) | 40 kW (55 PS) | 1937-1953 |
| | | |
BMW automotive engine directory
Design, development and variant notes
The M78 was BMW's first automobile straight-six, introduced in the 303. It uses a chain-driven camshaft in the block, pushrods and overhead valves, with an iron block and iron head.
The family grew from the early 303 version into several 315, 319, 326, 320 and 327 versions with different displacement, carburettor and compression specifications. The later M328 was the higher-performance companion.
Data adapted from the cited Wikipedia revision by Wikipedia contributors under CC BY-SA 4.0. Production dates and fitments reflect that revision; verify the exact engine code, market and vehicle before applying a specification.
Sources
Curated reference notes. Applicability follows the cited sources; hardware testing by this wiki is not implied.
Further Wikipedia-sourced details
The following additional information is drawn from the cited Wikipedia revision by Wikipedia contributors, available under CC BY-SA 4.0. An open-ended date reflects the source snapshot, not confirmed current production or fitment.
Additional technical and variant notes
The early 303 version is listed at 56 × 80 mm, 5.6:1 compression, 22 kW and 68 N⋅m. The later 327 version is listed at 1,971 cc, 6.3:1 compression and 40 kW; these figures describe different M78 versions.
Additional recorded applications
| Source version or rating | Vehicle application as recorded |
|---|
| Models / 303 version | 1933-1934 303 |
| Models / 319 version | 1937 329 |
| Models / 326 version | 1936-1946 326 |
| Models / 326 version | 1938-1950 321 |
| Models / 320 version | 1937-1938 320 |
| Models / 320 version | 1938-1941 321 |
| Models / 327 version | 1937-1955 327 |
| Models / 327 version | 1949-1953 340 |
Further specifications from the cited article
Additional facts are adapted from this Wikipedia revision by Wikipedia contributors, under CC BY-SA 4.0.
The M78 has an iron block and reverse-flow iron head, an in-block chain-driven camshaft, and overhead valves operated by pushrods and rockers. The source describes four bearings for both crankshaft and camshaft.
The 315 uses a 58 × 94 mm bore and stroke, 5.6:1 compression and 25 kW at 4,000 rpm. The 315/1 uses three Solex carburettors, 6.8:1 compression and is listed at 29 kW at 4,000 rpm.
The 1,911 cc 319 uses 65 × 96 mm dimensions and is listed at 33 kW at 3,750 rpm; the 319/1 is listed at 40 kW at 4,000 rpm. The UK Frazer Nash version used SU carburettors and the 319/3 code.
The 1,971 cc 326 uses 66 × 96 mm dimensions, two 26 mm Solex carburettors, 6.0:1 compression and 37 kW at 3,750 rpm. The single-carburettor 320 version is listed at 33 kW at 3,750 rpm. The 327 version is listed at 40 kW at 4,500 rpm and 104 N⋅m at 3,750 rpm.