GMC LD5 Specs: 3.799 x 3.402 in

See other engines in this family

The same engine also has a main page: Chevrolet LD5.

GMC LD5 specs: 231 ci (3.8L) 6-cylinder, 3.799 x 3.402 in (96.5 x 86.4 mm) bore and stroke, 8:1 compression. Built 1978–1984. Used in the Oldsmobile Cutlass.

The GMC 231ci (LD5) is oversquare — the 3.7992" bore exceeds the 3.4016" stroke by 11.7% — a layout that favors airflow and RPM over leverage at the crank. The 3.4016" stroke does not reach 4,000 ft/min of mean piston speed until about 7,050 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 38.5 ci (631 cc).

8:1 on iron heads is low by modern standards and generally happy on regular pump fuel.

5 factory variants share these dimensions across 1978–1984.

Dimensions

Displacement	231 ci / 3.8 L
Bore	3.7992"
Stroke	3.4016"
Cylinders	6
Configuration	V6
Compression ratio	8:1
Bore/stroke ratio	1.117

Construction

Block material	cast iron
Head material	cast iron
Valvetrain	OHV
Fuel type	gas
Years	1978–1984

What these numbers mean

Bore/stroke character	1.117 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves
Mean piston speed at 6,000 RPM	3,402 ft/min — conservative for a street engine
Displacement per cylinder	38.5 ci
Static compression	8:1 — low by modern standards, generally happy on regular pump fuel

Run the numbers for this engine

Each link opens the calculator with this engine's specs already filled in.

• Displacement from bore and stroke (calculator)
• Static and dynamic compression ratio calculator
• Piston ring gap for this bore
• Piston speed at any RPM
• What size carburetor (CFM calculator)

Variants sharing these dimensions (5)

These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.

Year	Advertised HP	Code
1978	—	LD5
1979	—	LD5
1981	—	LD5
1983	—	LD5
1984	—	LD5

What cars have the LD5?

23 factory vehicles, 1977–1987. Each year opens that model's engine table.

• Oldsmobile Cutlass: 1977, LD5, 105 hp; 1978, LD5, 105 hp; 1979, LD5, 115 hp; 1980, LD5, 110 hp; 1981, LD5, 110 hp; 1982, LD5, 110–115 hp; 1983, LD5, 110 hp; 1984, LD5, 110 hp; 1985, LD5, 110 hp; 1986, LD5, 110 hp; 1987, LD5, 110 hp
• Pontiac Firebird: 1977, LD5, 105 hp; 1978, LD5, 105 hp; 1979, LD5, 105–115 hp; 1980, LD5, 115 hp; 1981, LD5, 110 hp
• Pontiac LeMans: 1977, LD5, 105 hp; 1978, LD5, 105 hp; 1979, LD5, 115 hp; 1980, LD5, 115 hp; 1981, LD5, 110 hp
• Buick LeSabre: 1977, LD5; 1978, LD5; 1979, LD5; 1980, LD5; 1981, LD5; 1982, LD5; 1983, LD5; 1984, LD5; 1985, LD5
• Oldsmobile Starfire: 1977, LD5; 1978, LD5; 1979, LD5; 1980, LD5
• Pontiac Catalina: 1977, LD5; 1978, LD5; 1979, LD5; 1980, LD5; 1981, LD5
• Pontiac Phoenix: 1977, LD5; 1978, LD5; 1979, LD5
• Pontiac Sunbird: 1977, LD5; 1978, LD5; 1979, LD5; 1980, LD5
• Pontiac Ventura: 1977, LD5
• GMC Sprint / Caballero: 1978, LD5; 1979, LD5; 1981, LD5; 1983, LD5; 1984, LD5
• Buick Regal: 1978, LD5, 105 hp; 1979, LD5, 115 hp; 1980, LD5, 110 hp; 1981, LD5, 110 hp; 1982, LD5, 115 hp; 1983, LD5, 112 hp; 1984, LD5, 110 hp; 1985, LD5, 110 hp; 1986, LD5, 110 hp; 1987, LD5, 110 hp
• Chevrolet El Camino: 1978, LD5, 105 hp; 1979, LD5, 115 hp; 1980, LD5, 110 hp; 1981, LD5, 110 hp; 1984, LD5, 110 hp
• Chevrolet Malibu: 1978, LD5, 105 hp; 1979, LD5 / LC6, 115 hp; 1980, LD5, 110 hp; 1981, LD5, 110 hp; 1982, LD5, 110 hp; 1983, LD5
• Chevrolet Monte Carlo: 1978, LD5, 105 hp; 1979, LD5 / LC6, 115 hp; 1980, LD5, 110 hp; 1981, LD5, 110 hp; 1982, LD5, 110 hp; 1984, LD5, 110 hp
• Chevrolet Monza: 1978, LD5, 105 hp; 1979, LD5, 115 hp; 1980, LD5, 110 hp
• Oldsmobile 88: 1978, LD5; 1979, LD5; 1980, LD5; 1981, LD5; 1982, LD5; 1984, LD5; 1985, LD5
• Buick Skylark: 1978, LD5, 105 hp
• Pontiac Grand Am: 1979, LD5, 115 hp
• Pontiac Grand Prix: 1979, LD5, 105 hp; 1980, LD5, 110 hp; 1981, LD5, 110 hp; 1982, LD5, 110 hp; 1983, LD5, 110 hp; 1984, LD5, 110 hp; 1985, LD5, 110 hp; 1986, LD5, 110 hp; 1987, LD5, 110 hp
• Chevrolet Camaro: 1980, LD5, 110 hp; 1981, LD5, 110 hp
• Chevrolet Caprice: 1980, LD5, 110 hp; 1981, LD5, 110 hp; 1982, LD5, 110 hp; 1983, LD5, 110 hp; 1984, LD5, 110 hp
• Chevrolet Impala: 1980, LD5, 110 hp; 1981, LD5, 110 hp; 1982, LD5, 110 hp; 1984, LD5, 110 hp
• Pontiac Bonneville: 1980, LD5; 1981, LD5; 1982, LD5; 1983, LD5; 1984, LD5; 1985, LD5; 1986, LD5

Similar engines

• GMC 230 — 230 ci
• GMC Chevy Straight-6 (194/230/250/292) (1964) — 230 ci
• GMC LC3 — 229 ci
• GMC 235 — 235 ci
• GMC LLR — 223.9 ci
• GMC LLR — 223.9 ci
• Buick 3800 V6 · 3.799" × 3.402" · 9.4:1 — 231 ci
• Buick L36 — 231 ci

← All GMC 231ci engines