Found this to be a good read...
In the fall of 1977, GM introduced its 350-cu.in. diesel engine. The LF9-code mill was the only passenger-car V-8 diesel in the world at that time; Oldsmobile engineered it, but all GM divisions from Chevy to Cadillac used it. Even today it's reputed to be a converted gasoline engine, but it's not: While it shared some things like head-bolt locations and other machining points with gas engines, a consequence of manufacturing efficiencies, the block is a unique high-nickel-content iron casting, with beefier bulkhead and main-bearing sections.
The crank was nodular iron like those used in hi-po 455s, and the connecting rods started as 403 gas-engine pieces but have beefier ends and rods, and are a different length. Pistons were made from special high-strength "diesel piston aluminum" (good thing, since compression was 22.5:1) and cast by Bohn. The basic mechanical fuel-injection package, by the Roosamaster division of Stanadyne Corporation, had been proven some 11 million times on farm tractors. Two batteries were needed, one at each front corner, in part to help power up the glow plugs and for the 10hp starter motor. Power ratings were listed at 120hp at 3,600 RPM and 220-lbs.ft. of torque at 1,800 RPM; the power rating dropped to 105hp in 1981 despite the addition of a roller cam and lifters.
Contemporary reports downplayed it, but the thing rattled like a schoolbus, particularly when heard from outside the car; an extra layer of sound deadening on the firewall helped inside. And it was slow: A typical GM
B-body of the era would do the quarter-mile in the high-16-second range, but a diesel-powered
Delta 88 Royale took more than 20 seconds to trip the beams, at a paltry 69 MPH. Then there was the soot: Spitting out diesel particulate matter (unburned carbon compounds) gave them a reputation for being dirty and smelly; today, it's considered a carcinogen.
But none of this mattered: The second OPEC crisis kicked diesel use into high gear in this country, and Olds was selling as many as it could build, getting as much as 22 MPG on the highway for their 4,200-pound sedans. Eighteen percent of Oldsmobiles sold in 1981 alone were diesels.
Diesel engines have another trick up their sleeve: Reliability. They're overbuilt to take the stress of compression-ignition, operate at lower RPM than most gas engines (the Olds' redline was 4,000 RPM) and there are no distributors, wires or sparkplugs. It was foolproof. Right?
Mmmm...not so much.
GM's 10-head-bolt-per-side arrangement, shared with the gas engines and using torque-to-yield bolts, wasn't enough for the 22.5:1 compression; overheating, blown head gaskets and even broken head bolts were the result. And that was just the start. The chain on the mechanical fuel-injector pump stretched with normal use, making the pump deliver fuel too late. Crank bearings failed because well-meaning owners were putting in the wrong engine oil. A water separator was not included on the early LF9 fuel systems, and the steel guts of the fuel system, from the pumps to the injectors, would rust internally. Some owners added drygas (anhydrous alcohol) to the fuel to absorb the water, but the alcohol reacted with the governor rings inside the injection pump, causing the rings to flake off in chunks, and block the fuel lines. Combine this with dealership mechanics largely unfamiliar with diesel engines despite GM selling hundreds of thousands a year in the late '70s, and you've got some serious issues.
The 1981-up engines (with so-called DX blocks) were improved in many areas, including water filtration and a roller cam, but a class action lawsuit filed with the Federal Trade Commission meant that owners could claim 80 percent of the original cost of the engine in case of a failure. Combine this with the return of cheap gas, and the fact that power and performance were back in vogue by the mid-'80s, it's perhaps not surprising that the LF9 went away in 1985 with more than a million units sold.
This article originally appeared in the September, 2009 issue of Hemmings Motor News. 
