Detroit Clan

LG4
Years: 1980–1988*
The LG4 produced 150 hp (112 kW)-170 hp (127 kW) and 240 lb·ft (325 N·m)-250 lb·ft (339 N·m). The engine saw a series of gradual improvements, increasing reliability, mpg, and power output. In 1978, some GM models were available with the Rochester 4bbl M4ME carburetor, which offered a glimmer of some performance potential. For 1982, GM mandated that Pontiac discontinue their 301 V8 engines, resulting in a massive increase in LG4 production. Chevrolet also added GM's new "Computer Command Control" (CCC) engine management system to most LG4 engines, this included the very-efficient Rochester 4bbl E4ME Quadra-Jet, producing 145 HP @ 4000 RPM, 240 ft/lb @ 2000 RPM in the GM F-Body.145 hp (108 kW). In 1983, Chevrolet replaced the cast iron intake with an aluminum version and utilized either 14014416 ("416") or 14022601("601") heads with int: 1.84/ exh: 1.50 valves, 58cc chambers, 178cc runners. For 1985, the 4-valve-relief, flat top pistons from the L69 were added to the LG4. Also added was a knock sensor to allow the "CCC" engine management system to compensate for the increase in compression and a more aggressive spark timing map in the ECM. As a result power increased for the 1985 models to 165 hp (123 kW) from the 150 hp (112 kW) rating in 1984. For 1986, Chevy changed over to a 1 piece rear main seal engine block design to minimize leaks and warranty claims, however some early '86 blocks retained a 2 piece rear main seal. For 1987, Chevrolet once again made some revisions to increase overall reliability. An all-new electronic distributor design was used. The intake manifold to head bolt pattern was redesigned to improve gasket integrity. Changes to the valve covers were also made. "Ribbing" was added to the top of the valve covers to increase surface area, acting as a heat sink. To improve intake gasket sealing, the mounting bolts were relocated to the valve cover centerline, placing all sealing pressure evenly upon the mounting flange perimeter... thus these became known as "centerbolt valve covers". Another improvement was utilization of a hydraulic lifter/roller camshaft on most '87 LG4's. Some early engines have lifter retainer provisions, but utilize the older, non-roller camshaft. 1987 would also be the last year for the LG4 production, however... a run of LG4 engines was made to supplement the carry-over production for the 1988 Monte Carlo and the 1988 Caprice & Pontiac Pariseinne.

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