[rollinhard]

found this info on them on another forum
Quote:
LF9 Diesel

The LF9 was a 350-cubic-inch (5.7 L) Diesel V8 produced from 1978 to 1985.
Applications;

350N 1978-1985 Chevrolet, Buick, Oldsmobile, Pontiac, and Cadillac cars
Early 120 hp (89 kW) 220 ft·lbf (300 N·m) torque
Later 105 hp (78 kW) and 205 ft·lbf (278 N·m) torque
350N 1978-1980 GMC and Chevrolet light trucks "pickups"
125 hp (93 kW) and 225 ft·lbf (305 N·m) torque
Variations;

1978-1980 Early block Identified by "D" cast into both sides of block
Up to 125 bhp (93 kW)
external EGR from 1978-1981(single stud air cleaner)
internal EGR from 1982-1985(2 stud air cleaner)
Rumored that some early main and head bolt holes were not tapped to bottom
Used a conventional flat tappet hydraulic camshaft/flat tappet hydraulic lifters which required 3000 mile oil change intervals.
1981-1985 Improved block Identified by "DX" cast into both sides of block
Up to 105 bhp (78 kW)
Internal EGR
Fully tapped head bolt holes
Longer main bolts with fully tapped holes in block
Newly introduced roller lifters/rollerized camshaft extended oil change intervals.
Diesel differences;
The Oldsmobile diesel is believed by some to be a converted gasoline engine. While they share the same bore and stroke and some external bolt patterns (transmission and exhaust manifolds) they are quite different.
GM began with a substantially different bottom end when compared with its gasoline cousin.

Diesel blocks
3" diameter injection pump mounts are cast into the top of the lifter valley
Camshaft nose modified to incorporate injection pump drive gear
Block castings are much thicker and heavier. It's possible to overbore the cylinders by 0.125in without sonic testing.
Solid heavy cast main webs were used.
Reputedly GM used a higher nickel cast iron alloy for the block and heads.
Diesel crankshafts
Nodular Iron used in all Diesel cranks
Main bearing journals increased to 3.000"
Vibration damper modified to allow eccentric for crank-driven fuel lift pump
Diesel pistons and rods
Diesel rods are shorter at 5.886" long.
Diesel pistons have large valve reliefs and steel inserts behind the first compression ring.
Fuel systems;

No OEM fuel/water separator was factory installed on any Olds Diesel.
Crank eccentric driven fuel lift pump mounted in same location as gasoline fuel pump.
Fuel line heater between lift pump and filter.
Intake mounted 10 micrometre fuel filter.
Stanadyne Roosamaster DB2 mechanical diesel injection pump.
1978-79 Pencil Injectors held in by clamp.
1980-85 Poppet injectors screw into head.
Heads;

The same 10 head bolt pattern as their smallblock gasoline cousins.
The same exhaust manifold bolt pattern as their smallblock gasoline cousins.
Have injector pre-chambers and glowplug bosses.
Valve springs contained a vibration dampener with rotators.
Head variations;
Very early castings were stamped D3 and used 5/16" injector hold down retaining bolts and clamps.
D3A castings were created a little later and used 3/8" injector hold down bolts and clamps.
Both D3 and D3A heads accepted external EGR and pencil injectors.
Some D3A heads accepted poppet injectors as well.
D3B Later heads
All had internal EGR
Pencil or poppet injectors
1 or 2 locating dowels
The Oldsmobile diesel gained a reputation for unreliability and anemic performance that badly damaged the North American passenger diesel market for the next 20 years.[6][7]
[edit] Oldsmobile diesel problems

[edit] Head bolts

GM used "torque to yield", commonly known as "stretch" or "angle torque", head bolts. This allowed the bolt pattern to remain the same as the gas powered counterpart with an increase in clamping load when compared to standard head bolts. A total of 10 bolts per head were used. Four per cylinder with the center three pairs shared. This permitted the use of the same tooling and reduced setup costs. This design did not provide adequate clamping force under the severe conditions these engines were subjected to. Overheating or excessive cylinder pressure can breach the seal of the head gasket and in severe cases break the bolts.
High strength aftermarket head bolt sets are now available to make the engine more reliable in this area.
[edit] Pump timing

The Stanadyne pump was chain driven. With normal use, the chain stretches and the pump delivers fuel too late. The pump timing could be adjusted to return to normal operation.
[edit] Water in fuel

Arguably a major portion of the real problem would have been quite simple to avoid. A water separator was not part of the fuel system on these engines. A diesel run in an automobile will pick up water contaminated fuel.
Water will rust the steel internals of the fuel system. Rust will damage the precision parts in diesel fuel injection pumps and high pressure diesel injectors causing erratic operation. Injecting fuel too much prior to TDC on the compression stroke will cause pressure conditions similar to pre-ignition / detonation in gasoline engines. Water in varying amounts will also be injected with the fuel charge. Any rust in the steel fuel lines, fuel filter, pump etc can damage replacement parts and continue to cause injection cycles out of time.