Northstar engine series

The Northstar engine is a family of high-performance 90° V engines produced by General Motors between 1993 and 2011. 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.

Displacing 4.6 L (4,565 cc; 278.6 cu in) in its basic form, the direct family line transitioned to longitudinal and 4.4 L (4,371 cc; 266.7 cu in) supercharged versions. Variants were used at Oldsmobile (as the Aurora L47 V8 and "Shortstar" LX5 V6), as well as in several top-end 2000s Pontiacs and Buicks.

The related Northstar System was Cadillac's trademarked name for a package of performance features introduced in mid-1992 that coupled the 4T80E transmission, a 100,000 mile service interval, road sensing suspension, variable power steering, and 4-wheel disc brakes to the Division's high-output and high-torque Northstar engines.

GM ceased production of the Northstar in 2011. The final cars to receive it, the Cadillac DTS, Buick Lucerne, and Cadillac STS, rolled off the line in 2011. It was replaced by the GM LS small-block OHV engine, used in newer Cadillac V8 models like the CTS-V, marking a step back to a simpler, more reliable pushrod engine design. These LS V8 engines were the only V8 engines used by Cadillac for the next eight years, until the clean sheet Blackwing V8 was introduced in 2018 in the 2019 Cadillac CT6-V. A Cadillac-exclusive, it was discontinued after just two years in early 2020.

GM initiated what ultimately became the Northstar's design at Oldsmobile R&D^{[citation needed]} some time in 1984 in anticipation of^{[citation needed]} the advanced dual overhead cam V8 engines to be introduced by European and Japanese competitors later in the decade. 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. At the time it was GM's corporate policy not to pass the gas guzzler tax on to the consumer.

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. GM developed a laundry list of items to be included in the Allanté and updated Eldorado and Seville STS, including sophisticated steering, braking, and suspension technologies, and an engine exclusive to "Cadillac" the Division's dealers were clamoring for. This group of features became known as the Northstar System. Central to it was a high-tech V8 with the performance and sophistication to compete with an ever-expanding list of imported challengers.

Capable of producing 300 hp (224 kW) out of its 4.6 L (4,565 cc; 278.6 cu in) 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 lower crankcase assembly supported the crankshaft without conventional main bearing caps. An oil manifold plate with an integrated silicone gasket forms the oil gallery under this. A typical oil change used 7.5–8 US qt (7.1–7.6 L; 6.2–6.7 imp qt) of oil.

GM specified cast-iron cylinder liners and the cast aluminum pistons included valve clearance. Northstar is an interference engine: the valves will strike the pistons if they lose timing. It has bronze piston pin bushings and free-floating piston pins. GM used cast aluminum cylinder heads featuring 4 valves per cylinder. The heads used dual overhead cams driven through the "maintenance-free" cam-drive chain case. 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. The intake valves are inclined at 25°, while the exhaust valves are canted to 7° with center-mounted platinum-tipped spark plugs. The cam covers are magnesium for light weight and sound damping.