SD-220 R-Line truck engine
early 1950s100 hp gross / 90 hp net in 1953 manual
Entry Silver Diamond postwar truck six
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International Harvester SD-220 Six enginePhoto: Greg Gjerdingen · CC BY 2.0
International Harvester · Silver Diamond Inline-Six
International Harvester SD-220 Six
The compact Silver Diamond truck six used across International's postwar light and medium truck lines.
220.5
Cubic inches
The SD-220 was part of International's new postwar Silver Diamond family and became a common light-truck six before later Black Diamond/BG revisions.
Key variants
All variantsSD-220 R-Line truck engine
Displacement
220.5 ci
Bore
3.5625"
Stroke
3.6875"
Years
1949–1950s core Silver Diamond era
Key Takeaway
The SD-220 was part of International’s postwar Silver Diamond inline-six family. With a 3.5625-inch bore and 3.6875-inch stroke, it combined conservative dimensions, low compression, and cast-iron pushrod construction for dependable commercial-truck operation.
Technical Specifications
- Compression
- 6.5:1 in the 1953 R-Line factory service manual; later service/vehicle specifications reached about 7.0:1
- Horsepower
- 108 hp @ 3800 rpm in documented 1955 form
- Torque
- 173.5 lb-ft @ 2000 rpm maximum in the R-Line factory manual; 167 lb-ft net @ 1200 rpm
- Architecture
- OHV inline six
- Block
- Cast iron
- Cylinder heads
- Cast iron
- Valvetrain
- Pushrod OHV
- Aspiration
- Naturally aspirated
- Fuel delivery
- Carbureted
- Firing order
- 1-5-3-6-2-4
- Main bearings
- 4
The SD-220 was part of International’s postwar Silver Diamond inline-six family. With a 3.5625-inch bore and 3.6875-inch stroke, it combined conservative dimensions, low compression, and cast-iron pushrod construction for dependable commercial-truck operation.
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
- SD-220 (Silver Diamond 220)
- Casting numbers
- No single block/head casting is treated as universal across all SD-220 service production; verify SD-220 stamping, 3.5625 x 3.6875-inch bore/stroke and casting/date together.
- Power rating
- Factory manual lists both maximum brake horsepower and net brake horsepower
- Horsepower RPM
- 100 hp @ 3600 rpm maximum; 90 hp @ 3600 rpm net in the 1953 R-Line factory manual
- Torque RPM
- 173.5 lb-ft @ 2000 rpm maximum; 167 lb-ft @ 1200 rpm net
Operating Specs
- Production notes
- International’s R-Line factory manual lists the SD-220 at 220.5 cid with a 3.5625-inch bore, 3.6875-inch stroke, 6.5:1 compression and both gross and net output figures.
Compatibility Notes
- SD and later BD inline-sixes are related truck families, but displacement, crank/stroke, head and accessory details must be matched to the exact model.
- Commercial-truck governors, carburetors, bellhousings and accessories vary by chassis/application; use the engine model and truck model together when ordering parts.
Notable Applications
International L-series trucksInternational R-series trucksInternational S-series trucks
Strengths
- Simple durable truck design
- Good parts-family continuity
- Strong low-rpm manners
Weaknesses / Watch-outs
- Low specific output
- Four-main-bearing crank
- Limited modern performance aftermarket
Common Upgrades
- Carburetor restoration
- Electronic ignition
- Cooling-system refresh
Racing History & Legacy
The SD-220 was engineered for commercial-truck durability, not a factory racing campaign. Its significance is as a foundational postwar International gasoline truck engine.
The SD-220 helped define International’s postwar gasoline truck engine lineup and laid groundwork for the larger Silver Diamond and later Black Diamond families.
References & Image Credit
Engine image: Greg Gjerdingen · CC BY 2.0 · source
Key Factory / Build Variants
Engineering Notes Worth Knowing
01
3.5625 x 3.6875-inch bore and stroke; 220.5 cu in / 3.6 L.
02
Cast-iron OHV inline-six with pushrod valvetrain.
03
Factory-era output reached about 108 hp, with maximum torque around 173.5 lb-ft in R-Line service data.
04
Used in L-, R-, and S-series International trucks.
History · context · related reading
The Story Behind International Harvester SD-220 Six
After World War II, International needed modern gasoline sixes for its expanding light- and medium-truck lineup. The Silver Diamond family answered with straightforward overhead-valve engines designed around fleet durability and low-rpm drivability.
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