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Swap a 4.0L in for your 258

I figure if you're reading this you must have an older CJ or YJ and have grown to hate your carburetor. I have had four Jeeps with the good old 258 inline six in them. The motor itself is great off road because of its low-end torque and durability. My first '87 YJ had 230,000 miles on it when I sold it. I swore that I would never buy another carburated jeep. But as luck would have it, one day I stumbled upon an '87 Wrangler for sale for $2250. The jeep had 206,000 miles on it when I got it. I figured I could drive it until it died and then do an engine swap. Unfortunately, the thing just would not die. I even tried to force it a bit by not changing the oil, etc. At 250,000 miles I was tired of waiting and decided to do the swap.

But you could have had a V8!

Cole FordWhy swap in another six instead of a V8? I asked myself this question for about 18 months and here is my answer. I figured that the V8 would have been a fun swap but I would have to do a lot more modifications to my vehicle to handle it and to pass my local emissions laws. Upgrading to a newer 4.0L Jeep engine has tons of advantages. It is pretty much a straight bolt in project and with the fuel injection you gain power, driveability, gas mileage and off-road performance. (Not to mention that it starts and idles on very cold days; something my 258 just refused to do).

The Engine

There are basically two versions of the 4.0L Jeep motor. The engines made before '92 have a different interior head design than the later 4.0L. The 92 and up 4.0L s have a higher flowing head design that gives you just a tad bit more power. If you have a choice get the newer motor. If you find a steal on an older one I would take it just the same. I found it easier to get a motor out of a Cherokee than a Wrangler. (There are simply more of them in the salvage yards).

There is often a huge price difference between "Jeep" salvage places and "general" type salvage yards. Some of the Jeep places wanted upwards of $3000 for a 4.0L. I found 3 pre-'92 4.0Ls in regular salvage yards for around $500 including harness, computer, sensors and accessories. The '92+ engines cost a bit more but they were just as easy to find. I bought a '92 Cherokee 4.0L with computer, harness, sensors, and all the accessories for $850 with 78K on the motor. (I figured this is a pretty good deal, since it would have cost me about $2000 just to add the Multi Port Injection alone).

There are a few differences between the Cherokee and Wrangler 4.0L motors. The water-cooling fan setup in a Cherokee is offset. So if you want to run a mechanical fan you need to swap some pulleys and a water pump from a Wrangler. The Power steering reservoir is remote mounted on a Wrangler and it is part of the pump on a Cherokee. Either one will work, but the Cherokee set up is easier. The swap will be much easier if you have as much of the original motor as possible. You will need the COMPLETE harness. The flywheel is also mandatory, as the crank sensor on the flywheel determines your timing. After you have found a good motor, you are half the way there.




By Line Photo Courtesy of Claudine Cauori

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