TorqueList Original Technical Art
GMC 228 Inline-Six
Inline6 · N/A
GMC · GMC Low-Deck Inline-Six
GMC 228 Inline-Six
GMC's own light-truck six that replaced the earlier Pontiac-sourced engine and anchored prewar/postwar pickups.
228
Cubic inches
The 228 marked GMC's move to an in-house light-truck six and established the low-deck architecture shared with the 248.
Displacement
228 ci
Bore
3.5625"
Stroke
3.8125"
Years
1939–1953
Key Takeaway
The 228 used GMC’s early low-deck OHV straight-six layout with a 3.5625-inch bore and 3.8125-inch stroke. Its undersquare geometry, cast-iron construction, pushrod valvetrain, and carbureted induction were aimed at dependable low-speed truck service rather than high-rpm power.
Technical Specifications
- Horsepower
- About 95 hp in 1949 truck specification; later ratings around 100 hp
- Torque
- About 182 lb-ft in commonly cited late specification
- Architecture
- OHV inline six, low-deck GMC family
- Block
- Cast iron
- Cylinder heads
- Cast iron
- Valvetrain
- Pushrod OHV
- Aspiration
- Naturally aspirated
- Fuel delivery
- Carbureted
The 228 used GMC’s early low-deck OHV straight-six layout with a 3.5625-inch bore and 3.8125-inch stroke. Its undersquare geometry, cast-iron construction, pushrod valvetrain, and carbureted induction were aimed at dependable low-speed truck service rather than high-rpm power.
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
- Simple durable truck architecture
- Good low-speed torque
- Strong period GMC identity
Weaknesses / Watch-outs
- Four-main-bearing low-deck design
- Limited modern performance aftermarket
- Lower displacement than later GMC sixes
Common Upgrades
- Electronic ignition conversion
- Carburetor restoration
- Dual exhaust or period intake upgrades
Racing History & Legacy
The 228 became the starting point for GMC’s low-deck inline-six family and directly set the pattern for the larger 248. Its importance is less about headline horsepower than about establishing the durable GMC truck-six formula that followed.
References & Image Credit
Engineering Notes Worth Knowing
3.5625 x 3.8125-inch bore and stroke; 228 cu in / 3.7 L.
Low-deck GMC OHV inline-six architecture with cast-iron block and head.
Period output was roughly 95–100 hp depending on year, with about 182 lb-ft commonly cited for later specifications.
Used across GMC light-duty pickups and 100–250 series commercial trucks.
History · context · related reading
The Story Behind GMC 228 Inline-Six
Introduced before World War II and carried well into the postwar truck boom, the 228 helped establish GMC’s own six-cylinder identity. It was sized for light and commercial truck work, with simple construction and torque-focused manners that fit the job GMC expected it to do.
TorqueList Garage Reference Series
See this engine inside the full GMC reference catalog.
The same Engine Library data now powers a more detailed mobile-friendly catalog with technical specs, variants, engineering notes, history and related stories.