THE 1962-1987 BUICK V-6 STORY

Chopping two cylinders from the Buick Aluminum V-8 may have seemed simple, but it was way more complex than that.

The first Buick V-6 was introduced in 1961 for the 1962 model year Buick Special. It would be 198 CID and became the first V-6 in an American car , though a separate design GMC V-6 was used earlier in trucks. Because it was derived from Buick’s 215 CID aluminum V8, it has a 90° bank between cylinders and an uneven firing pattern due to the crankshaft having only three crank pins set at 120° apart, with opposing cylinders (1-2, 3-4 and 5-6) sharing a crank pin as many V8 engines do. The uneven firing pattern was often perceived as roughness, mostly noticeable at idle.

Later, in 1977, Buick redesigned the crankshaft to a “split-pin” configuration to create an “even-firing” version. The crank pins associated with the opposing cylinders were offset from each other by 30°. The relatively small offset did not require any special design, but 0.12 in thick flange was built in between the offset crank pins to prevent the connecting rod big-ends from “walking” off the crank pin bearing journal and interfering with the adjacent big end.

Otherwise, the engine block remained unchanged compared to the previous odd-fire engine. Since the cylinders center-lines were no longer centralized over the crank pin bearing journals, the connecting rods were re-designed with the big-ends offset from the piston pin ends by 0.059 in.

The off-center design continued up until the 1988 LN3 version of the engine, when the left-hand bank of cylinders was moved forward relative to the right-hand bank. Although the actual bore spacing between cylinders on the same bank remained unchanged at 4.24 in, the LN3 and later engines became known to have “on-center bore spacing”.

The 1962 V-6 cutaway in more detail. While its influence from a design point of view was the aluminum V-8, the 300-340 CID V-8 of 1964-67 owes it design to this engine.

225 CID

In 1964, the bore was increased to 3.75 in, and stroke increased to 3.4 in, increasing the size to 225 CID. Since the engine was similar to the popular small-block Buick V8 — now with a cast-iron block and displacement of 300 cubic inches, both engines could now be made with less expense than the aluminum counterpart, and at the same factory with most of the same tooling. This engine was used in Buick’s intermediate-sized Special and Skylark models from 1964 to 1967 and Oldsmobile’s mid-sized F-85/Cutlass models for 1964 and 1965, including the Oldsmobile Vista Cruiser and Buick Sport Wagon.

The 1964-1965 models featured a single barrel Rochester MonoJet, producing 155 HP. In 1966-1967, the 1-barrel was replaced with a 2-barrel Rochester 2GV, giving the engine a 5-horsepower boost to 160 HP. The V-6 was dropped after the 1967 model year in favor of a conventional 250 CID inline-six cylinder engine built by the Chevrolet division, and the tooling was sold to Kaiser-Jeep.

Kaiser “Dauntless” V-6

In 1965, Kaiser-Jeep began using the Buick 225 in Jeep CJs. It was known as the Dauntless V-6 and used a much heavier flywheel than the Buick version to damp vibrations resulting from the engine’s firing pattern. In 1967, Buick sold the tooling for this engine to Kaiser, as GM management consolidated their six cylinder inventory, a mistake they would later realize. When American Motors (AMC) bought Jeep from Kaiser, the V-6 was replaced with AMC I-6 engines, but the ownership of the V6 tooling remained with AMC.

Kaiser/AMC Applications:
• 1966–1971 Jeep Jeepster & Jeepster Commando
• 1966–1971 CJ-5
• 1966–1971 CJ-6

231 CID

The 1973 oil crisis prompted GM to look for more economical engines than the V-8s of 350, 400 and 454/455 cubic inches that powered most General Motors cars and trucks during that time. At that time, the only “small” engines generally offered by GM were built by the Chevrolet division including the 140 CID Over Head Cam aluminum inline-four engine used in the subcompact Chevy Vega and a 250 CID I-6 used in smaller Chevy, Buick, Oldsmobile and Pontiac models, whose design roots dated back to the 1962 Chevy II.

At that point and knowing their forthcoming chassis sizes might preclude the longer I-6 from use, Buick engineers took an old Fireball V-6 and installed it in a 1974 smaller sized Buick Apollo, built on the older Chevrolet Nova chassis. The solution worked so well that Buick convinced GM to ask AMC to put the engine back into production. However, saw this as a nuisance, and set their cost per unit high, which GM recognized would be too high for profitability.

Instead of buying completed engines, GM offered to buy back the tooling and manufacturing line from AMC in April, 1974. That deal was accepted, and GM began building the engines in August of that year, a move made possible by the fact that foundations for the old V6 machinery were still intact at Buick’s engine assembly plant in Flint, Michigan. This allowed Buick to put the purchased tooling back in place and begin production at least two years ahead of the normal schedule that would have been necessary if they has to recreate all the tooling.

Once production back within GM, Buick re-introduced the V-6 in the fall of 1974 in certain 1975 models The bore was enlarged to 3.8 in, identical to the Buick 350 and Olds 307 V8s, yielding 231 CID. 78,349 units were installed in Buicks for 1975, an amazing feat. Due to difficulties with the new fuel economy and emissions standards, the engine produced 110 SAE HP.

LD5 3.8 L V-6

In 1978, GM began to market the 231 as the “3.8 Liter”. The RPO Engine Code was LD5, though California-emissions versions were called LC6. Starting in 1979, the engine was used in the front-wheel drive Buick Riviera, though still with a longitudinal mounting. Larger valves and better intake and exhaust boosted the power output for 1979.

The 3.8 Turbo V-6 first appeared in the 1978 Regal and LeSabre

The turbo 3.8 liter was used in the following vehicles:

• 1978–1987 Buick Regal Sport Coupe, T-Type, Grand National, Base T, Limited T, Turbo T, and GNX
• 1978–1980 Buick LeSabre Sport Coupe
• 1979–1980 Buick Century Turbo Coupe & Sedan
• 1979–1985 Buick Riviera S-Type, T-Type and less than 100 Convertibles
• 1980–1981 Chevrolet Monte Carlo Turbo
• 1989 Pontiac Trans Am Turbo 20th Anniversary Edition

LC9

A smaller version of this engine was produced in 1978 and 1979 for the Century, Regal and Chevrolet Monza. The bore was reduced to 3.5 in resulting in an engine of 196 CID or 3.2 L. The RPO code was LC9. Initially this engine produced 90 HP SAE Net, but in 1979 it received the same improvements in the cylinder heads as did the LD5, and therefore power increased to 105 HP.

LC4

In response to rising gas prices, a larger 252 CID version of the 3.8 liter LD5 V-6 was produced from 1980 through 1984 and marketed as an alternative to a V8. The bore was enlarged to 3.965 in or 4.1 L, yielding an output of 125 HP and 205 lb⋅ft of torque. This engine was used in many large rear-wheel drive Buicks, and in some models from each of GM’s other divisions, including Cadillac which offered the 4.1 Liter from 1980 to 1982 as a credit option to the troublesome Cadillac V-8-6-4 engine used in 1981 as well as early versions of the aluminum-block Cadillac HT-4100 V8 introduced in 1982.

It was also the standard powerplant in the front-drive Riviera and Oldsmobile Toronado from 1981 to 1984. This was the first naturally aspirated GM V-6 to feature a 4-barrel carburetor.

The Buick V-6 would go through many changes until abandoned in the early 2000s, including even throw crankshaft, supercharging and more. It was hugely versatile, sturdy and reliable, a testament to its original designers and their foresight.