Join Date: Sep 1999
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Re: Diesel swap
The diesel engine that you will want for a Jeep, will greatly depend on what you plan on doing with the Jeep.
It really sucks when you go through all the work of putting a diesel in your Jeep (and it is a lot of work) and you take it out the first time and you have that feeling in your stomach that this is just not what you expected. I have been there twice now.
Back in 1990 when i first built my Jeep, I installed a brand new 4 cylinder Isuzu in my stock CJ7. This engine did not have a turbo on it and was very gutless on the road. It would only do about 55 with a tail wind. Off-road it was acceptable, and it did get 20 mpg consistently.(with 31" tires and 3.54 gears)
After I got sick of that engine i replaced it with a 6.2L diesel. Off-course the 6.2 was better, but it still did not impress me. It would go faster on the road, but it still took it awhile to get there. Off-road it also did very well, and also got close to 20 mpg. (31" tires and 3.07 gears)
After that engine busted a valve, I replaced it with a 4 cylinder Perkins diesel. This is a very tall engine, so that is when i had to go SOA, just to get it to fit. This engine had some issues and I only put about 2000 miles on it before i replace it. It sucked on the road (top speed was 65) and i never tried it off-road. It did get close to 24 mpg though.(31" tires and 4.11 gears)
Next came the current 6.5L turbo diesel. IMHO, this is the best engine to ever put in a SWB Jeep. It weighs about 150 lbs more than a SBC, will so 0-60 in about 10-11 seconds, will do 100+mph, and still gets between 18-24 mpg. It has had the stock axles in it, so it has not went off-road, but I cant see any drawbacks there either.
The problem with the diesels that have already been mentioned. The mercedes and VW-hard to mate a tranny to it. The Cummins and Perkins 4 cylinder is a very heavy engine(close to 800 lbs), a much slower engine (redline 2500-3000) and does not have the hp or torque of the 6.5L diesel.
So if you are planning on only using the Jeep as an off-road vehicle a 4 cylinder diesel would be sufficient. But if you want a Jeep that will be a DD and off roader you would want a higher speed diesel, I would not go with a 4 cylinder, unless it has a turbo on it.