A 350 Diesel Swap..In a Jeep Cherokee

Heres some info sent to me from Tom Karnowka, a man who has sucessfully converted a Jeep Cherokee with a 2.8 V6 to a 350 Diesel..he is from Littleton Colorado. If anyone is interested in doing a conversion like this here is all the info you will need!...he Writes: I want to tell you about my 1985 Jeep Cherokee. I'm an electrical engineer, and my father (a mechanical engineer) has a machine shop that enabled us to do a very clean conversion of putting a 1984 Olds 350 into the Cherokee. This project took 3 months to complete, but went quite smoothly. The Cherokee is a very light car (about 2500lb) and the front suspension was designed to handle the weight of a 2.8L V6. We had to rebuild much of the front suspension (with larger coil springs) to withstand the weight of the 350, and the overall suspension was raised by 3" to accommodate decent clearance between the engine starter and front differential. We engineered a way to maintain proper steering geometry so the car is actually very stable at 75MPH even with the 31"-diameter 10"-wide tires. Here's a summary of the items we had to address in doing the conversion: (1) Bell housing adapter from Advanced Adapters in California - designed to use a Buick 3.8L V6 in place of the Chevy 2.8L originally used by Jeep - was a direct bolt-up match to the 350 diesel, with the exception of the location of the starter. The Olds 350 has the starter on the driver side, while the Buick 3.8L has it on the passenger side. But a little creative aluminum cutting and welding enabled us to move the non critical "hump" in the bell housing to the other side. The transmission is the Toyota AX5 5-speed manual that Jeep originally used in this car (2) Custom-made radiator to provide 6-layer efficiency in very small space. The fiberglass front clip was hollowed-out from the inside and reinforced with metal frame to allow the radiator to fit snuggly within the front clip. Another metal frame was built to hold the front grill about 1.5" forward of its original position - it actually looks better than the original Jeep placement of the grill. (3) Brake booster was changed to GM hyrdro-boost type, since there is no useable vacuum on the diesel engine, besides the low volume coming from the little pump. That low volume pump is just used to actuate the heater/vent flappers. Brake master cylinder was also changed to GM type to mate with the hydro-boost unit. (4) Two Subaru electric fans were mounted side-by-side between the front of the engine and the radiator, with no fan mounted to the water pump pulley. The Subaru fans seemed to be the only ones with the motor embedded into the hub of the fan, giving minimum thickness of the overall fan unit - a requirement to fit in this tight conversion. (5) In conjunction with using the oversized tires, the front and rear axle ratios were changed to 3.07:1 type to prevent overrevving the 350 diesel at highway speeds. (6) A Gates (now known as Optima) battery is used to start the engine. For decent starts in cold weather, the 350 needs two "normal" parallel-plate batteries to be connected in parallel to give enough cranking power for sufficiently fast compression change to promote combustion. One Gates battery does the job equally well. The only problem is that this overstresses the battery beyond its design specs, and I have to replace the battery every three years. (7) The cast iron exhaust manifolds of the 350 were used, but had to be cut and welded to provide different location of the exit fittings. Nickel rod arc welding provides excellent strength on the cast iron, and no cracking has ever occurred. A well known exhaust shop fabricated a fully custom single 2" exhaust system for the car, together with a junction to bring the pipes from each individual manifold. The workmanship on the exhaust was first-rate and definitely looks factory installed. A very large, oversized, muffler was used to allow quite operation while maintaining good flow through. (8) Removed nylon/plastic fuel screen inside the fuel tank and fabricated a similar screen out of brass mesh. The nylon/plastic/whatever could have dissolved with diesel fuel. This warning came from a diesel-head friend of ours. (9) We added a large (3.5" x 6") primary fuel filter/water separator under the hood connected after the fuel pump but before the input to the secondary (originally with the engine) filter. We installed a Carter electric fuel pump in place of the original mechanical pump, to facilitate easier priming and improve fuel delivery when 4-wheeling. Another small diesel-grade fuel filter was installed at the fuel tank. This car has been in full day-to-day use since we completed the conversion in September 1992. The engine now has 180K miles on it, and the car has 223K miles on it. We've taken it 4-wheeling about a dozen times or so, and have pulled a very small trailer a few times, but basically the workload has been very light. Since the total stress on the engine is extremely light due to the light weight of the car, we expect this engine to last well past 250K miles. It has passed diesel emissions tests effortlessly each year. About the biggest problem we've had is that the transmission can't withstand the torque of the diesel engine. We've had to replace/rebuild it every 50K miles. First of all, the 350 diesel didn't have the crank shaft bored out for a pilot bearing (needed for manual transmission). So we rigged up a jig that bolted up to the engine mounts (where the transmission would normally be fastened) and supported a precision X/Y cutting tool holder from a metal lathe. We then ran the engine on a frame and used the engine's own power to cut a true-to-center hole and snap ring groove in the end of the crank shaft for the pilot bearing. The first flywheel we attempted was from an AMC eagle or something like that (found at junk yard - it was about the right size). We machined the outside of the flywheel to fit the ring gear from a 350-diesel automatic transmission flywheel. We then cut the ring gear off the automatic flywheel and removed all weld marks that existed. The flywheel went into the freezer for a couple of hours, and we heated the ring gear in the oven. This allowed a precision fit of the two, and when the temperature equalized, there was no way of separating the two (this is how most ring gears are attached to manual transmission flywheels). We then had to drill new holes in the center of the flywheel to match the pattern of the 350 diesel crank. This flywheel worked, but was too far out of balance and caused major chassis vibrations at several different RPMs. We then found a flywheel from the 260 V8 diesel (which was sold with a 5-speed) and this offered excellent balance for the 350 with no vibrations. Tom Karnowka Littleton, CO

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