1978–1988 GM G-Body Engine Identification Guide
When General Motors redesigned its midsize A-Body lineup for 1978, it reclassified them as the new G-Body platform. Lighter, smaller, and more efficient than their predecessors, these cars carried the muscle car torch into the 1980s. Models included the Chevrolet Malibu and Monte Carlo, Pontiac Grand Prix, Oldsmobile Cutlass Supreme, Buick Regal, and later performance trims like the Monte Carlo SS and Buick Grand National.
While the late 1970s and early 1980s were marked by tightening emissions standards, GM still offered a variety of engine options across the G-Body lineup. From the four-cylinder Iron Duke to the revived high-output 305s, these engines provided a range of performance and fuel economy options.
Inline-Four Cylinders
Pontiac Iron Duke 151ci (2.5L) I4
Years: 1978–1984
Output: ~85–90 hp
Applications: Base models, especially in Pontiacs.
Notes: Very rare in G-bodies — most buyers upgraded to at least a V6.
V6 Options
Buick 231ci (3.8L) V6 — Naturally Aspirated
Years: 1978–1987 (various trims)
Output: 110–150 hp depending on year/carburetion/CCC controls
Applications: Base engine in Buick Regal, Olds Cutlass, Chevy Malibu, and Pontiac LeMans/Grand Prix.
Notes: This was the bread-and-butter six-cylinder for the G-body, replacing inline-sixes. By the mid-80s, most base models carried this motor.
Buick 231ci (3.8L) Turbocharged V6
Years: 1978–1987 (in performance Regals)
Output:
Late 70s/early 80s carbureted turbos: ~165–175 hp
1984–87 Sequential Fuel Injection turbos: 200–245 hp (Grand National, T-Type, Turbo-T, GNX)
Applications:
1978–83 Regal Sport Coupe (carbureted turbo)
1984–87 Regal T-Type / Grand National (fuel-injected turbo)
1987 GNX: 276 hp officially (but closer to 300+ hp in reality)
Notes: The Buick Turbo V6 is legendary. By 1987, the Grand National GNX was faster than most V8 muscle cars of the era, running mid-13s stock and often much quicker with light mods.
Chevy 200ci / 229ci (3.3L / 3.8L) V6
Years: 1978–1984
Output: ~95–115 hp
Applications: Entry-level Chevys (Malibu, Monte Carlo).
Notes: These were basically small-blocks with two cylinders lopped off. Simple, durable, but not powerful.
Chevy 4.3L (262ci) V6
Years: 1985–1988
Output: ~130–140 hp
Applications: Monte Carlo, Malibu, El Camino in later years.
Notes: Essentially a 350 small-block with two cylinders removed. This engine became the foundation for later GM trucks and SUVs.
The G-Body Small Block Lineup
267ci Small Block V8 (RPO codes: L39, LG4 in early years)
Years available: 1979–1982
Output: ~120–125 hp, ~190 lb-ft torque
Carburetion: Rochester Dualjet 2-bbl
Application: Entry-level V8 for Chevrolet Malibu, Monte Carlo, Pontiac LeMans, and other base G-bodies.
Notes: The 267 was essentially a downsized small-block meant for fuel economy. Bore size was so small (3.5”) that it limited valve size, choking performance. Identifiable by the smaller Rochester 2-barrel carb and casting marks on heads.
305ci Small Block V8 – Standard Variants
The 305 (5.0L) was the bread-and-butter small-block of the G-Body platform. Offered in multiple configurations, it became the most common small-block found under these hoods.
LG3 – 305ci 2-Barrel
Years available: 1978–1982
Output: ~140–150 hp, 240 lb-ft torque
Carburetion: Rochester Dualjet 2-bbl
Application: Base V8 in Malibu, Monte Carlo, and Pontiac/Oldsmobile/Buick G-body variants when equipped with a Chevy-built small-block.
Notes: Easy to spot by its 2-barrel carb and relatively modest power ratings.
LG4 – 305ci 4-Barrel
Years available: 1978–1988
Output:
150 hp (late 1970s)
165–170 hp (early 1980s)
150–155 hp (mid-1980s, after emissions recalibrations)
Carburetion: Rochester Quadrajet 4-bbl
Application: Found across the board in G-bodies, especially popular in Monte Carlo and El Camino.
Notes: The most common G-body small-block. Typically identified by VIN code “7” for the LG4.
305ci High-Output (HO) Variants
L69 – 305ci HO 4-Barrel
Years available: 1983–1986
Output: 190 hp @ 4800 rpm, 240 lb-ft torque
Carburetion: Rochester Quadrajet 4-bbl (specific calibration for performance)
Application: Monte Carlo SS, Pontiac Grand Prix 2+2, some Cutlass and Regal performance trims.
Notes: This was the top dog small-block of the G-body era. Identified by VIN code “G”. Often paired with 3.73 gears, dual exhaust, and F41 suspension packages.
307ci Oldsmobile Small Block (Note)
Although technically not a Chevrolet small-block, many G-bodies came equipped with the Oldsmobile 307 (VIN code “Y” or “9”) in Cutlass, Regal, and Grand Prix models. It’s worth mentioning because enthusiasts often swap them for Chevy 305/350s.
350ci Small Block V8 (RPO LM1)
Years available: 1978–1980 (very limited in G-bodies)
Output: 170–185 hp depending on year and emissions equipment
Carburetion: Rochester Quadrajet 4-bbl
Application: Rare in G-bodies, mainly in early Malibus and wagons, plus fleet/police packages.
Notes: After 1980, the 350 was phased out of G-bodies due to emissions and fuel economy targets. VIN code “L” identifies LM1 cars.
Identification Tips
Engine pad stampings: On Chevy small-blocks, look at the passenger-side front pad below the cylinder head. This shows suffix codes tied to RPO options.
Intake & carb: Dualjet = 2-bbl 305/267, Quadrajet = 4-bbl LG4/L69/LM1.
VIN codes: The 8th digit of the VIN quickly narrows down which engine your G-body left the factory with.
Emissions equipment: Air pumps, EGR, and catalytic converters were common—especially after 1981, when Computer Command Control (CCC) systems were introduced.
Quick Facts
The L69 305 HO was the most performance-oriented small-block G-body engine (Monte Carlo SS, Grand Prix 2+2).
The LM1 350 was rare and only offered very early (’78–’80), often in wagons or fleet/police packages.
After 1981, most engines were tied into CCC (Computer Command Control) emissions systems, easily spotted by electronic Q-Jet carbs and feedback wiring.
GM G-Body Engine Reference Chart (1978–1988)
VIN Code Guide (8th Digit of VIN)
| Engine (CID / L) | Type | RPO Code | Years | VIN Code | HP Range | Notes / Applications |
|---|---|---|---|---|---|---|
| 151ci (2.5L) I4 “Iron Duke” | Inline-4 | LQ9 | 1978–1984 | A | 85–90 hp | Rare base engine, mostly Pontiac models |
| 200ci (3.3L) V6 | Chevy V6 | LC3 | 1978–1979 | U | ~95 hp | Short-lived entry-level V6 |
| 229ci (3.8L) V6 | Chevy V6 | LC3 | 1980–1984 | A | 110–115 hp | Monte Carlo/Malibu base engines |
| 231ci (3.8L) V6 NA | Buick V6 | LC2 (var.) | 1978–1987 | 3, A | 110–150 hp | Most common base G-body engine |
| 231ci (3.8L) Turbo V6 | Buick V6 Turbo | LC8 (carb), LC2 (EFI) | 1978–1987 | 3, 9 | 165–245 hp | Regal Sport Coupe, T-Type, Grand National, GNX |
| 262ci (4.3L) V6 | Chevy V6 | LB4 | 1985–1988 | Z | 130–140 hp | Successor to 229 V6, based on SBC architecture |
| 260ci (4.3L) Diesel V8 | Olds Diesel | LF9 | 1979–1981 | N | 90–105 hp | Rare; Cutlass/Regal economy option |
| 267ci (4.4L) V8 | Chevy Small Block | L39 | 1979–1982 | X | 120–125 hp | Economy small-block; very limited |
| 305ci (5.0L) V8 2-bbl | Chevy Small Block | LG3 | 1978–1982 | Y | 140–150 hp | Common base small-block |
| 305ci (5.0L) V8 4-bbl | Chevy Small Block | LG4 | 1978–1988 | 7 | 150–170 hp | Most common G-body V8 |
| 305ci (5.0L) HO V8 | Chevy Small Block | L69 | 1983–1986 | G | ~190 hp | Monte Carlo SS, Grand Prix 2+2 |
| 307ci (5.0L) V8 | Olds Small Block | LV2 | 1980–1988 | Y (std), 9 (HO) | 140–180 hp | Common in Cutlass/Regal; HO in 442, Hurst/Olds |
| 350ci (5.7L) V8 | Chevy Small Block | LM1 | 1978–1980 | L | 170–185 hp | Very rare in G-bodies; police/wagons |
| 350ci (5.7L) Diesel V8 | Olds Diesel | LF9 | 1978–1985 | N | 105–120 hp | Cutlass, Regal, GP — poor reputation |
Big Picture by Brand
Chevrolet → 267, 305s, rare 350, 200/229/262 V6s.
Buick → 231 V6 (NA + Turbo), Olds 307, Olds Diesel options.
Oldsmobile → 260/307 gas V8s, 260/350 diesels.
Pontiac → Iron Duke 4, Chevy/Olds engines by the 80s.
The G-body platform was truly diverse, spanning from the wheezy 2.5L Iron Duke four to the Buick GNX Turbo V6 monster. By the late 1980s, the spotlight shifted from small-block V8s to the turbocharged sixes and special trims like the 442, GNX, and Monte Carlo SS.
If you need any parts for your GM G-Body, hop on SS396.com or give our friendly techs a call at (203) 235-1200!
