S22 Firedome 291
1955185 hp / 245 lb-ft
Two-barrel mainstream version
TorqueList Original Technical Art
DeSoto 291 Hemi
V8 · N/A
DeSoto · FireDome / FireFlite Hemi
DeSoto 291 Hemi
The 1955 DeSoto Hemi that enlarged bore and added a 200-hp four-barrel FireFlite version.
291
Cubic inches
The 291 was the one-year bridge between DeSoto's original 276 and the longer-stroke 330/341 engines, while the FireFlite version pushed DeSoto to 200 hp.
Key variants
All variantsS22 Firedome 291S21 Fireflite 291
Displacement
291 ci
Bore
3.72"
Stroke
3.344"
Years
1955
Key Takeaway
The 291 enlarged DeSoto's original Hemi by increasing bore to 3.72 inches while retaining the 3.344-inch stroke. Standard two-barrel and higher-output four-barrel versions gave the one-year engine a useful performance step before the taller-deck family arrived.
Technical Specifications
- Compression
- 7.5:1
- Horsepower
- 185 hp @ 4400 rpm Firedome; 200 hp @ 4400 rpm Fireflite
- Torque
- 245 lb-ft @ 2800 rpm Firedome; 274 lb-ft @ 2800 rpm Fireflite
- 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
- Two- and four-barrel carburetion
- Firing order
- 1-8-4-3-6-5-7-2
- Main bearings
- 5
The 291 enlarged DeSoto's original Hemi by increasing bore to 3.72 inches while retaining the 3.344-inch stroke. Standard two-barrel and higher-output four-barrel versions gave the one-year engine a useful performance step before the taller-deck family arrived.
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
- S21 (1955 Fireflite 291 4-barrel), S22 (1955 Firedome 291 2-barrel)
- Casting numbers
- 1558929 (291 block reference), 1613608 / 1616608 (291 cylinder-head references), 1616833 (291 2-barrel intake reference), 1557141 / 1617178 (291 4-barrel intake references)
- Power rating
- SAE gross (period factory rating)
- Horsepower RPM
- 185 hp @ 4400 rpm Firedome; 200 hp @ 4400 rpm Fireflite
- Torque RPM
- 245 lb-ft @ 2800 rpm Firedome; 274 lb-ft @ 2800 rpm Fireflite
Operating Specs
- Production notes
- For 1955 DeSoto enlarged the 276 bore to 3.72 inches while retaining the 3.344-inch stroke, creating the 291. Firedome used a two-barrel version while Fireflite received a four-barrel calibration.
Compatibility Notes
- The 291 shares the short-deck DeSoto Hemi intake family with the 276; later 330/341/345 tall-deck intakes are wider and do not directly interchange.
- Use the S21/S22 block stamp together with casting/date information because external early-Hemi appearance alone is not sufficient for accurate identification.
Notable Applications
1955 DeSoto Firedome1955 DeSoto FireFlite
Strengths
- Larger bore than 276
- Factory four-barrel performance version
- Compact first-gen Hemi character
Weaknesses / Watch-outs
- One-year displacement
- Original induction parts can be scarce
- No broad interchange with other early Hemi families
Common Upgrades
- Four-barrel induction
- Electronic ignition
- Exhaust improvements
Racing History & Legacy
The 291 was primarily a one-year production evolution of the DeSoto Hemi rather than a dedicated factory competition engine. Its performance role was to move the family toward the larger 330/341 Adventurer combinations that became DeSoto’s headline high-speed engines in 1956.
The 291 expanded the original short-deck DeSoto Hemi and introduced a stronger Fireflite four-barrel performance step immediately before the 1956 tall-deck redesign.
References & Image Credit
Hot Rod — Hemi engine sizes
technical history
Hemmings — 1955 Firedome 291
historical reference
Over-Drive Magazine — AMA/brochure-backed 1955 DeSoto 291 specifications
period spec compilation
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 intake casting numbers
specialist technical reference
Hot Heads — DeSoto short-deck and tall-deck intake compatibility
aftermarket technical reference
Over-Drive Magazine — 1952–1961 DeSoto V8 engine facts
period spec compilation
Key Factory / Build Variants
S21 Fireflite 291
1955200 hp / 274 lb-ft
Four-barrel higher-output version
Engineering Notes Worth Knowing
01
291 cu in / 4.8 L with 3.72 x 3.344-inch bore and stroke.
02
90-degree OHV DeSoto Hemi with dual rocker shafts.
03
Two- and four-barrel carburetion.
04
Factory ratings: 185 hp / 245 lb-ft Firedome and 200 hp / 274 lb-ft Fireflite.
History · context · related reading
The Story Behind DeSoto 291 Hemi
The 291 was a one-year bridge, but an important one. It pushed the original DeSoto Hemi to 200 horsepower and set up the larger, longer-stroke engines that followed.
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