S26A 345 Adventurer
1957345 hp / 355 lb-ft
Dual-quad one-horsepower-per-cubic-inch standard-production DeSoto flagship
.jpg)
DeSoto 345 Adventurer Hemi enginePhoto: Greg Gjerdingen · CC BY 2.0
DeSoto · Adventurer Hemi
DeSoto 345 Adventurer Hemi
The final and most powerful factory DeSoto Hemi: 345 cubic inches and 345 horsepower with dual quads.
345
Cubic inches
The 345 Adventurer reached one horsepower per cubic inch with its standard production engine, making the 1957 Adventurer a landmark American performance car before DeSoto moved to wedge engines.
Key variants
All variantsS26A 345 Adventurer
Displacement
345 ci
Bore
3.8"
Stroke
3.8"
Years
1957
Key Takeaway
The 345 used square 3.80 x 3.80-inch dimensions, 9.25:1 compression, dual four-barrels, and DeSoto's mature tall-deck Hemi heads. The combination delivered an advertised one horsepower per cubic inch in regular production form.
Technical Specifications
- Compression
- 9.25:1
- Horsepower
- 345 hp @ 5200 rpm
- Torque
- 355 lb-ft @ 3600 rpm
- Architecture
- 90-degree OHV Hemi V8
- Block
- Cast iron
- Cylinder heads
- Cast iron
- Valvetrain
- Pushrod OHV with dual rocker shafts
- Aspiration
- Naturally aspirated
- Fuel delivery
- Dual four-barrel carburetion
- Firing order
- 1-8-4-3-6-5-7-2
- Main bearings
- 5
The 345 used square 3.80 x 3.80-inch dimensions, 9.25:1 compression, dual four-barrels, and DeSoto's mature tall-deck Hemi heads. The combination delivered an advertised one horsepower per cubic inch in regular production form.
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
- S26A (1957 Adventurer 345 dual four-barrel)
- Casting numbers
- 1635779 (345 cylinder-head reference), 1735785 / 1736044 (345 crankshaft references); S26A block stamp is the primary displacement/application identifier
- Power rating
- SAE gross (period factory rating)
- Horsepower RPM
- 345 hp @ 5200 rpm
- Torque RPM
- 355 lb-ft @ 3600 rpm
Operating Specs
- Production notes
- For 1957 DeSoto bored the tall-deck Adventurer Hemi to a square 3.80 x 3.80-inch combination. Dual Carter WCFB four-barrels, a high-lift cam, larger valves, stiffer springs, modified pistons and strengthened rotating components supported the 345-hp rating.
Compatibility Notes
- The 345 belongs to the tall-deck 330/341/345 DeSoto Hemi group; use tall-deck-specific intake and swap hardware rather than 276/291 short-deck pieces.
- S26A identification is important because 1957 DeSoto also used 341 Hemi and Dodge-derived 325 engines; valve covers or general external appearance alone are not sufficient identification.
Notable Applications
1957 DeSoto Adventurer
Strengths
- 345 hp factory rating
- Dual-quad induction
- Square 3.80 x 3.80 dimensions
- Top DeSoto performance pedigree
Weaknesses / Watch-outs
- Extremely scarce original parts
- Complex dual-rocker Hemi valvetrain
- Collector pricing
Common Upgrades
- Preservation-focused rebuild
- Modern internal materials
- Careful carburetor synchronization
Racing History & Legacy
The 345’s significance is a production-performance milestone rather than a famous sanctioned-race victory: the 1957 Adventurer delivered an advertised 345 hp from 345 cid as standard equipment, placing DeSoto among the earliest American production cars to offer one advertised horsepower per cubic inch as standard.
The 345 was the largest and final first-generation DeSoto Hemi. It capped the division’s five-year Hemi development arc before DeSoto switched to Chrysler’s corporate B-series wedge architecture for 1958.
References & Image Credit
Engine image: Greg Gjerdingen · CC BY 2.0 · source
Hemmings — 1957 Adventurer 345/345
historical reference
Hot Rod — Hemi engine sizes
technical history
Over-Drive Magazine — AMA/brochure-backed 1957 DeSoto 345 specifications
period spec compilation
National DeSoto Club — 1957 Adventurer one-horsepower-per-cubic-inch history
club history
Quality Engineered Components — DeSoto early Hemi engine ID codes
specialist identification reference
Quality Engineered Components — DeSoto Hemi cylinder-head casting numbers
specialist technical reference
Quality Engineered Components — DeSoto Hemi crankshaft references
specialist technical reference
Hot Heads — DeSoto short-deck and tall-deck intake compatibility
aftermarket technical reference
National DeSoto Club — 1957 Adventurer and engine history
club history
Over-Drive Magazine — 1957 DeSoto AMA/brochure-backed specifications
period spec compilation
Over-Drive Magazine — 1952–1961 DeSoto V8 engine facts
period spec compilation
Key Factory / Build Variants
Engineering Notes Worth Knowing
01
345 cu in / 5.7 L with square 3.80 x 3.80-inch bore and stroke.
02
Tall-deck DeSoto OHV Hemi with dual rocker shafts.
03
Dual four-barrel carburetion.
04
Factory rating: 345 hp and 355 lb-ft.
History · context · related reading
The Story Behind DeSoto 345 Adventurer Hemi
The 1957 Adventurer 345 was DeSoto's Hemi program at its peak. One advertised horsepower per cubic inch made it a landmark engine just before the division abandoned its unique Hemi family for corporate wedge power.
TorqueList Garage Reference Series
See this engine inside the full DeSoto 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.