The Oldsmobile Quad 4 was introduced with high hopes, but the double-overhead cam engine never lived up to expectations.

Introduced on the 1988 Oldsmobile Cutlass Calais and Pontiac Grand Am, the Quad 4 was an ambitious effort to produce an up-to-date four-cylinder engine with four valves per cylinder and double-overhead camshafts—features other global automakers had already adopted. General Motors called the new powerplant “a milestone in engine design,” and for GM it was. Its previous DOHC four was the short-lived Cosworth Vega.

With the promise of greater volumetric efficiency and higher specific output, the Quad 4 was adopted by all the GM car divisions except Cadillac in a host of applications. The hope was that with its greater efficiency, the new four could replace the corporation’s aging V6 and V8 engine lines in passenger cars. In its original LD2 form, the engine was rated at 150 horsepower at 5,200 RPM and 160 lb-ft at 4,000 rpm.

Work on the Quad 4 had actually begun some years earlier, back in 1982, at the Oldsmobile division—this was the last engine developed in-house by Olds personnel. Reportedly, the 92 mm bore and 85 mm stroke dimensions were selected as the largest that could reasonably fit in a transverse, front-wheel drive package, the primary application. Thus the Quad 4 was a bit large for an inline four with an initial  displacement of 2.3 liters (137.9 cubic inches). Larger-displacement fours have a reputation for  roughness due to their greater secondary imbalance forces.

As was the practice, the block was cast iron while the head and other components were aluminum. Noteworthy features included a tuned-length intake manifold, accessory belt drives at both ends of the engine, hydraulic valve followers, and chain-driven camshafts. Under the finned aluminum cover and Quad 4 logo on the top of the engine  was an integrated ignition system with a single coil and no distributor, nestled between the cam towers and directly over the spark plugs,

Included in the ambitious plan was a turbocharged, intercooled Quad 4 (above) with 250 horsepower, as seen in the Cutlass Supreme Convertible concept that paced the 1988 Indy 500. No turbocharged Quad 4 ever made it to production, but there were normally aspirated high-performance versions, including the LG0 of 1989-94 with up to 180 hp and the 1991-93 W41 with 190 hp, later downrated to 185 hp. Conversely, there was also a low-balled L40 variant with a single cam, eight valves, and 120/115 hp that briefly saw production in ’92-’93.

While its production run was a respectable 14 years, the Quad 4 was a qualified success at best. Head gasket, timing chain, ignition, and other troubles persisted. And despite a number of attempts to address them through the years, the engine never overcame its isues with NVH—Noise, Vibration, and Harshness. In contrast to the silky DOHC fours from Japan and Germany at the time, the Quad 4 came off as thrashy and unrefined. The addition of balance shafts in 1995 and a rebranding as the Twin Cam in 1996 didn’t fix it. In 2002, GM replaced the Quad 4 aka Twin Cam with the Ecotec engine family.