TorqueList Technical Reference
LA Small-Block
Mopar 273 LA V8
The compact-bore LA that launched Chrysler's lighter small-block era.
273
Cubic inches
Why it matters
Key takeaway
The 273 introduced the LA small-block architecture that evolved into the 318, 340 and 360 and later underpinned the Magnum V8 family.
Key variants
Engineering
Technical specification
- Architecture
- 90-degree OHV V8
- Block
- Cast iron
- Cylinder heads
- Cast iron
- Valvetrain
- Pushrod OHV, 2 valves per cylinder
- Aspiration
- Naturally aspirated
- Fuel delivery
- Carbureted
- Firing order
- 1-8-4-3-6-5-7-2
The 273 launched Chrysler's LA small-block family with a compact 3.625-inch bore, 3.31-inch stroke, and conventional cast-iron pushrod architecture. Its smaller bore kept the engine light and compact, while the basic block design became the foundation for later 318, 340, and 360 engines.
Builder reference
Internal Specifications
Variant-specific values are labeled. For engine families with multiple factory combinations, the exact RPO/code/year takes priority over the family summary.
Identification & Output
- Engine codes / RPO
- A828 (factory development code associated with base 273), A861 (factory development code associated with 273 Power Pak/Commando), E31 (1969 273 2-barrel body-data-tag engine code)
- Casting numbers
- 2463252 (273 LA reference), 2465330 (1964–66 273 LA reference), 2536130 (1965 273 LA reference), 2806030 / 2806130 (1965–69 273 LA references)
- Power rating
- SAE gross (period factory ratings)
- Horsepower RPM
- 180 hp @ 4200 rpm standard; 235 hp @ 5200 rpm Commando/Power Pak
- Torque RPM
- 260 lb-ft @ 1600 rpm standard; 280 lb-ft @ 4000 rpm Commando/Power Pak
Operating Specs
- Production notes
- Introduced for 1964, the 273 was Chrysler’s first production LA-series small-block and established the architecture later expanded into the 318, 340 and 360.
Compatibility Notes
- LA-family small-block parts interchange is broad but not universal; verify crank/flywheel balance, cylinder-head bolt/port details, timing cover, oil pan and accessory drive by exact year.
- Early 273 heads and intake-port sizing differ from later performance LA combinations; verify bore and valve clearance before fitting larger-valve heads.
Factory fitment
Notable applications
Versions that matter
Key factory / build variants
273 2-barrel
Mainstream compact LA small-block version
1964–1969
Application/year dependent
273 Commando / Charger 273
Factory performance version that established the LA family’s sporting reputation
mid-1960s
High-performance 4-barrel versions
Strengths
- Compact dimensions and low weight for a traditional iron V8
- Shared LA-family architecture makes it historically important
Watch-outs
- Smaller bore limits cylinder-head and valve choices compared with later LA engines
- Performance-specific original parts can be harder to find
Common upgrades
- Four-barrel intake and carburetor
- Dual exhaust
- Period-correct camshaft upgrade
Builder notes
Engineering notes worth knowing
273 cu in / 4.5 L with 3.625 x 3.31-inch bore and stroke.
90-degree OHV V8 with cast-iron block and heads.
Carbureted in standard and higher-output four-barrel versions.
The first production member of the LA small-block family.
History & context
The story behind the engine
The 273 matters less because of its displacement than because of what came after it. It introduced the LA architecture that Chrysler would keep developing for decades.
Racing history
The 273 had genuine road-racing credentials in the first SCCA Trans-Am season. A 273-powered 1966 Plymouth Barracuda Formula S campaigned by Chrysler engineer Scott Harvey finished second in the championship, giving the small LA engine an early competition chapter before the 340 became Chrysler’s better-known small-block performance engine.
Legacy
The 273 established the basic LA architecture that became one of Chrysler's longest-lived V8 families.
Verification
Reference sources
Stellantis Mopar brand history
manufacturer history
MaxWedge — Chrysler/Mopar engine bore and stroke reference
specialist technical reference
Mopar Enthusiast Network — 1966–1974 engine specification chart
historical specification
Mopar Performance electronic ignition instructions — Chrysler V8 firing order
manufacturer instruction
Mopar engine block casting-number reference
specialist reference
1969–1974 Mopar body-data-tag engine code reference
historical code reference
Hot Rod — 273 Power Pak factory specifications and development codes
historical technical reference
Hagerty — 1966 Barracuda Formula S Trans-Am competition history
historical motorsport reference
Hagerty — 1966 Barracuda Formula S Trans-Am history
historical motorsport reference
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