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Wire, Water & Juice - Engine Swap Tips - 4-Wheel & Off-Road Magazine

Fred Williams Brand Manager, Petersen’s 4Wheel & Off Road

In our Mar. ’13 issue we gave you some insight on do-it-yourself engine swaps (“Easy Engine Exchange”). This month we’ll continue with some points on three fundamental parts to making your engine run: wiring, cooling, and fuel. These three components can make or break the enjoyment of your new repowered 4x4.

wire Water And Juice Engine Swap Tips engine And Project Truck Photo 48458082
All the intricate, time-consuming, expensive steps of wiring and plumbing

A lot of 4x4 owners dream of a nice V-8 under the hood of their 4x4 but fear the little things that make it work well. It’s easy to measure and weld in motor mounts, set the engine square in the frame with enough clearance by the firewall and forward enough to have a reasonable rear driveshaft. But then comes all the intricate, time-consuming, expensive steps of wiring and plumbing, and before you know it frustration sets in.

wire Water And Juice Engine Swap Tips radiator Photo 48458085 Having enough cooling for your engine is an issue we engine swappers encounter in garages and on trails across the nation. We went to the experts at Advance Adapters for our radiator. With over 40 years of experience helping wheelers swap parts into their 4x4, these guys have seen it all. In fact, our request for a radiator to put a Chevy V-8 in a Jeep was about as mundane as can be, and the company’s crossflow aluminum radiator fit perfect in our CJ grille. Mounting holes are not drilled, so you can adjust the height in the grille as desired. Note the blue caps on the right side of the radiator; these are fittings for an internal transmission cooler, where we will plumb in our 4L80E transmission.

The secret to wiring and plumbing is to find easy-to-use kits and really take your time installing them. Rushing the little steps will just cause more work down the road, or on the trail. Hopefully these products and pointers will help avoid those pitfalls.

wire Water And Juice Engine Swap Tips cj 10 Grille Photo 43226647 Our CJ is a retired military CJ-10, so it has a goofy grille with no headlights since they are on the fenders. Oddball-looking, but these grilles will allow even more cooling airflow, so you may want to look into one if you’re stuffing a big-block in a ’70s-’80s CJ-5, -7, or -8. PhotosView Slideshow Wiring for late-model, fuel-injected engines can be scary. A lot of sensors are required to make them run so smooth and consistent. Shown here is the factory harness. You could try and sort out the wiring yourself if you had the time and a wiring diagram to determine what wires to keep, but that is something we will save for another article. Because we are swapping in an ’03 GM 6.0L V-8 (a pretty common engine swap due to its good power and simple installation), we opted to source a harness for the swap. Many companies offer harnesses for these GM Gen III and IV LS series engines, but we chose Pacific Fabrication (Pac Fab) because those guys not only do a lot of LS engine swaps at their shop but they are also four-wheelers, so they understand the performance needed off-road. The new harness is cleaner, svelte, and labeled for ease of installation. It has easy-to-read instructions and an included fuse block for the engine. The entire harness can be installed on the engine itself in under 20 minutes by a novice. The powertrain control module (PCM) is another important factor in late-model engine swaps. We sent ours to Pac Fab, where they reflashed it to work with our swap based on a questionnaire about transmission, tire size, gearing, and other details. The PCM controls both the engine and the transmission in a stock application, and because we are using the factory automatic transmission that came behind the 6.0L from our donor vehicle our PCM will keep the transmission control parameters. Without fuel getting to your engine your project is nothing more than a garage ornament. Fuel-injected engines require fuel pumps that put out higher pressure than those of old carbureted engines. We found that the late-model Jeep TJ (’05-’06) in-tank fuel pumps put out about 60 psi of pressure, and we like in-tank pumps because, while they can be harder to replace, being submerged in fuel helps cool and protect the pumps from burning up. We sourced a new fuel sending unit from Rock Auto to go in our GenRight Long Range 24-gallon aluminum fuel tank. The Pac Fab wiring harness has a large-gauge wire that will power the fuel pump when keyed on. We marked the in-tank pump for positive, ground, and the terminals for the fuel gauge. We will find a factory TJ harness plug to make a clean, snap-together wiring connection. The fuel rails of Gen III engines like ours have two fuel lines, a feed and a return (arrows). Gen IV GM engines “dead head,” with a single feed on the rail and no pressure regulator or return at the engine. We sourced a Gen IV fuel rail from Pac Fab to swap onto our 6.0L for easier plumbing. To get the fuel from the in-tank pump to the single feed fuel rail we again called up Pac Fab for the company’s new LS fuel plumbing system. This kit includes hard fuel line, heat shield, some hose, various fittings, and a fuel regulator/filter. It is also available with an external fuel pump if you do not have or want an in-tank pump. The hose fittings in the kit are high-pressure push-lock style. They have -6 couplings to attach to the fuel rail adapters. The fuel rail adapters (also used at the regulator/filter and fuel tank) are a simple push-on locking fittings. These may require a small dab of oil on the fuel rail for ease of assembly. Inline between the fuel pump and the engine is the fuel pressure regulator/filter combo unit. This has an inlet fitting and return fitting on one end and an outlet fitting on the other end. The high-pressure fuel feeds into the unit, where it is regulated to 58 psi. What fuel isn’t needed is returned to the tank, while the regulated fuel feeds through to the fuel rail on the engine. The return line will be plumbed into the fuel tank via a splice in the fuel filler neck. The Pac Fab plumbing kit requires a tubing cutter and bender and a flare tool for the 3⁄8-inch hard line. Running hard line for the fuel has the benefit that if flared and mounted safely, it should have no leaks and not deteriorate or lose pressure, as can happen over time by running hose. Though we did run hose at the engine to allow some movement of the powertrain, and a short section at the fuel tank to allow for easy removal, the rest will be hard line.

Not Done Yet
One aspect of late-model engine swaps that a lot of people forget is tuning. OEMs spend hundreds of thousands of hours tuning engine parameters in late-model vehicles to get them to run perfectly. Though it is possible to get an engine running and driving in your 4x4 with an off-the-shelf PCM tune, there is often room for improvement. Pacific Fabrication reminded us that after we have our project truck up and running we should take it to a qualified local dyno tuner where they can tweak and tune the computer to get optimal performance to our specific needs. Some tuners will even go out four-wheeling with you to get the best running engine for your desired wheeling style, but expect to pay extra for this service.