Regarded as GM's most technically complex engine, the original double overhead cam, four valve per cylinder, aluminum block/aluminum head V8 design was developed by Oldsmobile R&D, [citation needed] but is most associated with Cadillac's Northstar series.

At that time, Cadillac was using the aluminum HT Overhead Valve (OHV) V8 which GM pushed hastily into production because the CAFE standards for 1982 would preempt using 1981's V8-6-4.

Cadillac was developing new models which they hoped would compete against the best luxury cars from BMW, Mercedes-Benz, and Asian rivals like Lexus, Acura, and Infiniti.

Capable of producing 300 hp (224 kW) out of its 4.6 L; 278.6 cu in (4,565 cc) displacement, the Northstar featured a cast aluminum 90° V8 block with 4 in (101.6 mm) bore spacing split into unitary upper and lower halves.

The cams act directly on hydraulic lifters on the ends of the valves and are fed with a lubrication passage drilled through the cylinder head lengthwise.

Although this was intended to prolong alternator life, GM reverted to a traditional air-cooled setup for 2001 to eliminate potential leak points and extraneous tubing.

Later developments included direct coil-on-plug ignition, roller lifters, and variable valve timing, which can vary intake by up to 40° and the exhaust by up to 50°.

VVT was devised for the longitudinal LH2 version, and was not used on the transverse front wheel drive engines due to packaging considerations.

The engines were revised for 2000 with coil-on-plug ignition and roller follower valvegear for improved fuel economy and reduced emissions.

For better head gasket sealing between cylinders, the supercharged version is de-bored to 91 mm (3.58 in) for a total displacement of 4.4 L; 266.7 cu in (4,371 cc).

The 4.6L V8 engine found in models from 1995-2005 were notorious for failure due to a design flaw involving the use of torque-to-yield bolts in the head gasket.

The high load of the engine would eventually cause these bolts to weaken and loosen in their threads, rupturing the seal and in turn blowing the head gasket.

The engine topped out at 300 hp (224 kW) from 1996 through 2004 on the STS, DTS and ETC models, making these some of the most powerful domestic front wheel drive cars ever built.

[citation needed] For 2005 the L37 was named "Northstar NHP", and was downrated to 290 hp (216 kW) under the new SAE certified horsepower rating system.

It was modified substantially in 2004 for longitudinal rear- and all-wheel drive use in the STS, SRX, and XLR, as well as receiving continuously variable valve timing on both intake and exhaust sides.

Although most of the Northstar's features, including the coolant loss system, remained intact, the decreased bore increased weight unacceptably.

To reduce it, Oldsmobile used a one-piece glass-filled thermoplastic intake manifold and simplified AC Rochester sequential fuel injection.

A highly modified 650 hp (485 kW) version of this engine was used by General Motors racing division initially for IMSA sports car competition in an Oldsmobile Aurora GTS-1 and Riley&Scott LMP prototypes in 1995, Indy Racing League competition starting in 1997, then was later used in the Cadillac Northstar LMP program in 2000.

It has chain-driven dual overhead cams and four valves per cylinder, but is an even-firing design with a split-pin crankshaft similar to the Buick 3800 engine.

It was said at the time that a family of premium V6s would follow, with displacements ranging from 3.3 L to 3.7 L, but only the LX5 was ever produced before GM discontinued the Shortstar in favor of their current flagship V6, the High Feature engine, in 2004.

The LX5 was entirely different from any other V6 in the GM inventory - the only other DOHC V6 engines ever offered by GM included the Chevrolet Twin Dual Cam produced from 1991-1997, which was made by modifying the traditional Chevy 60-degree OHV block V6 for the dual overhead cams rather than building a DOHC engine from the ground up, and the Cadillac/Holden HFV6 available from 2004 to the present day.

These three designs are completely unrelated and leave two gaps in 1998 and 2003 where no DOHC V6 was available from GM (except for the 54 degree Opel V6 used most notably in the first generation Cadillac CTS at launch as well as the Saturn L Series and Catera).