5.7L Oldsmobile Diesel
350 ci Olds Diesel Specs & Info
designed and built the 5.7L Olds diesel in response to the oil crisis of the late 70's. First appearing in 1978, the 350 ci diesel promised the creature comforts of a large vehicle with the fuel mileage of a compact. Officially named the LF9 diesel, the Olds diesel found its way into Chevrolet, Buick, Pontiac, Oldsmobile, & Cadillac car lineups, as well as light duty Chevrolet & GMC trucks. The engine proved unreliable & problematic overall. Coupled with a generation of consumers who were unfamiliar with diesel engines, the engine was removed from production despite majority of the flaws being addressed. The 350 ci Olds diesel is responsible, in part, for giving diesel engines a poor reputation & setting a grim image for diesels that would last long into the future. Aftermarket solutions have since proven that the 5.7L can be transformed into a very capable, fuel efficient engine.
5.7L Olds Diesel Specs
Chevrolet, Buick, Pontiac, Oldsmobile, & Cadillac cars. GMC & Chevy light duty trucks.
350 cubic inches, 5.7 Liters
indirect injection (IDI)
naturally aspirated, non-turbo
125 HP @ 3,600 RPM
225 lb-ft. @ 1,800 RPM
Unreliable, problematic. Regardless, the engines do have a following of fans/enthusiasts and most problems can be eliminated with upgrades.
Common Olds Diesel Problems
• Torque to yield (TTY) head bolts provide poor mounting of the cylinder heads. As a result, head gaskets can wear & fail. Head bolts were even known to sheer under the extreme cylinder pressures (the Olds diesel had a very high compression ratio, which didn't help).
• The fuel system lacks a fuel-water seperator. Any water that enters the injection pump can cause parts to corrode & fail. This can result in extensive engine damage.
• Main bolts were too short, often resulting in bottom end failure & crankshaft damage. Crankshafts were not dynamically balanced, further contributing to crankshaft failures.
• GM was in a rush to offer their diesel and be the automaker to "pioneer" the industry. As a result, production of the engine blocks for the 5.7L Olds was rushed. After casting, the "green" (green is a term used to describe a casting that has not had proper time to cure) engine blocks were rushed to assembly before the internal stresses could be relieved. This caused problems with the engines once they were run, as the heat cycles caused engine blocks to flex, often causing misalignment of the main bores. Misaligned main bores contributed to the common crankshaft failures.
Additional Olds Diesel Information
• Though the Olds diesel shares many design similarities with the 350 ci gasoline engine, they are completely different engines. They do not use the same block, and the internals are completely different. Because they share the same bore & stroke as the 350 gasser, people commonly assume the 2 engines share a uniform design. They could, however, be manufactured with pre-existing tooling. Various GM publications have stated that "All of the major parts: block, crankshaft, rods, pistons, and lifters have been strengthened to handle the higher compression ratio."
• The 350 diesel Olds made Popular Hot Rodding's "Worst Automobile Engines of All Time".
• The 5.7L diesel was designed to increase fuel mileage in GM's product line, and was estimated to provide up to 30 mpg in certain applications.
• Some drag racers have been known to use 350 diesel blocks as their platform for a 350 ci gasoline engine build, because the blocks are much stronger in high horsepower applications.