Taking a Four-Cylinder TJ to V-8 Power
Preaching the Converted
Driving an underpowered Jeep on the trail or down the road is something that people have been doing since the first army prototypes were tested. Even though V-8 power was made an option for some Jeeps in the early '70s, there are still plenty of underpowered wheezers out on the road today. Even Jeep's latest version of those first military Jeeps, the TJ, has been determined by some to be gutless enough to need a V-8 engine under the hood. This is especially true if your TJ is equipped with the 2.5L four-cylinder. If your base-model four-banger TJ needs more fire under the tires, or your 4.0L fuel-injected six can't muster up the strength to run the dunes, a V-8 swap may be just the ticket for you. Sounds complicated and expensive, huh? Well, don't worry--there are plenty of people who have walked the line in search of more Jeep power, and they've done it all, despite the difficulties of modern emission controls, for a lot less money than it takes to make a Dodge Durango as capable off-road as an almost stock Wrangler. We recently got the opportunity to follow along as the Jeep V-8 conversion experts at Advance Adapters converted a '97 2.5L TJ into a fire-breathing Chrysler 5.2L V-8-powered beast. Here are some of the details, a few tips and, of course, some helpful tricks.
To start out, you've got to have a Jeep in need of a V-8, and the Jeep we had was in serious need of more power. The factory 2.5L was just barely able to spin 35-inch Mickey Thompson tires. A TJ is a good candidate for a V-8 because of its super-sturdy boxed frame, multi-linked coil suspension, and plenty of room under that round, bulging hood. Knowing a V-8 was in order, there was still lots of research to be done and many things to be considered before any wrenches were turned. Our TJ is a California car, so emissions mandated that we find a '97-or-newer V-8 donor vehicle. The people at Advance Adapters decided to use a DaimlerChrysler-based V-8 for a few reasons. One: The wiring between Dodge and Jeep V-8s is similar to our Wrangler. Two: The bolt pattern and spline count on the back of a Dodge or Jeep manual or automatic transmission behind a 5.2L or 5.9L matches up to a NV231J or, in our case, a 4.3:1 Atlas II that had been previously swapped in.
The last stipulation was that the owner of the Jeep wanted a manual transmission behind his V-8, and Grand Cherokees with a V-8 and a manual transmission are rare, if not non-existent. The search began for a '97-or-newer wrecked, preferably hit from behind, manual-transmissioned 4x4 Dodge Dakota, Durango or 1500-3500 truck with a 5.2L or a 5.9L V-8. What we found was an '01 Dodge 1500 4x4 with an NV3500 transmission.
Computers, Gismos and Widgets
Once you locate a possible donor truck, you need to make sure that you can get a few things from it:
* First and most obviously, we wanted the engine and transmission, but we also needed the engine accessories, pulleys, pumps, shifters and all of the emissions equipment and electronics. This means charcoal canisters, leak detection pumps, wiring and computers. Getting these parts now will be much easier, and much less expensive, than if you try to obtain them piece by piece later on.
* Even if emissions is not a concern of yours, the computer may go berserk if it does not have all of the emissions equipment hooked up at the end of the swap.
* Another thing to look into is if your auto dismantler will not unplug the wiring connectors on the donor vehicle for you; offer to do it yourself. The connectors are very important because the wiring schematics of the factory service manuals reference the plugs, not hacked-up wires.
* If the V-8's automatic overdrive transmission is to be used, make sure you have an automatic overdrive computer, but if you want to use a manual or a non-computerized automatic transmission, then you should use the manual transmission's V-8 computer.
* Grab the Dodge Y-pipe and catalytic converter. They are good pieces to start with when fabricating the exhaust once the engine is in your Jeep.
Getting Air In and Out
An air intake system was fabricated using a combination of Dodge Durango and Wrangler parts. The Durango parts, one PN 4883598AA (bonnet, throttle-body air inlet), one PN 4883599AA (hose, from air cleaner to throttle body), one PN 53031572AB (air cleaner bracket) and one PN 6504488 (nut) were used along with the stock TJ air box and a reducer. You could also use an aftermarket conical air filter in place of the TJ air box.
Lastly, the stock Dodge Y-pipe was modified for front driveshaft clearance and bolted to the stock Dodge exhaust manifolds. Then the Dodge catalytic converter and a new muffler were added along with a custom coffee-can tailpipe that finishes the system.
Despite the fact that almost any modern Jeep to modern V-8 conversion is always going to be a bit of a chore, the folks at Advance Adapters feel that this is one of the simpler swaps, and it should be doable in a driveway by any competent Jeep nut. In the end, the benefits of such a conversion include a factory-like install with readily available parts. Taking the little bitty 2.5L four-cylinder out of a Jeep Wrangler and swapping it for 5.2L of American V-8 power sounds good to us--can anyone say "Vrrrrooom?"