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  4. LS1 V-8 Jeep TJ Swap Part 2: The Running Details

LS1 V-8 Jeep TJ Swap Part 2: The Running Details

TJ LS1 V-8 Conversion: Part II

Bruce W. SmithPhotographer, Writer

Engine swaps have been a part of the Jeep community since the first flatfenders landed in civilian hands. That’s because Jeepers are consummate gearheads and hot rodders, and seldom settle for “stock,” especially when their beloved rides have a lot of years and hard miles under their wheels.

Such is the case with our 16-year-old TJ with a well-used factory 4.0L and manual transmission. The old Wrangler had seen a decade on the street and another six years on the rocks. Although the stock engine, transmission, and transfer case were adequate for such use, all needed rebuilding. However, instead of spending the money to get back the same level of performance, we decided it was time to ditch the stock six for a V-8 so we could hold our head high when hitting the sand, mud, or playing on the rocks. We also wanted bulletproof performance on a budget—a Jeepers version of having one’s cake and eating it too. It’s not an easy undertaking, so we turned to the Jeep experts at Dunks Performance in Springfield, Oregon, to help with the transplant.

Quick Refresh

In our first installment (“TJ LS1 V-8 Swap”), shop owner Mike Dunks and his crew outlined the critical hard parts and showed us the steps needed to slip a junkyard ’02 Camaro LS1 V-8 into the tight confines of the TJ’s engine bay.

We relied heavily on Advance Adapters for the proper engine mounts to make the LS1 fit properly on the frame rails while fitting in the space the 4.0L had vacated. We also bit the bullet and slid in its Atlas 2 transfer case behind the used TH400.

We skirted the biggest roadblock with such swaps by yanking out the 4.0L EFI’s engine wiring and replacing it with Holley Performance’s plug-and-play standalone EFI system that’s carefully engineered and packaged for GM LS1/LS6 engine swaps.

Another hurdle to overcome with a 4.0L-to-LS1 transplant is engine cooling. That was easily handled using a Flex-a-lite LS Conversion radiator, a direct bolt-in unit with a 15-inch Black Magic electric fan that flows 3,000 cfm through the custom aluminum radiator.

Holley Connection

Older wrench turners who weren’t weaned on bytes might be intimidated by the idea of trying to get a standalone engine control system and LS1 talking to each other. Don’t sweat it. If you can turn on a laptop, your can fire up this engine swap without a single call to a “help” desk.

Holley’s kit includes very detailed step-by-step instructions on paper and CD that makes the electronic connection between its engine control module (ECM) and the LS1 simple for even a novice. The kit really is as close to plug-and-play as one will find today.

“The ‘Help’ section on the Holley CD walks you through the steps needed to make the ECM connect to the sensors on the LS1,” says Eric Dunks, an ASE-certified master technician. “This is very similar to other EFI systems we’ve used. It’s very user friendly, and all the connections are tagged so it completely takes the guesswork out of the wiring.

“What makes the Holley unit convenient is it already has preprograming for the LS1, so all you do is check the box on the drop-down menu that applies to your engine,” said Dunks. “Holley has one pull-down menu that allows you to select which cam is being used. Our engine’s cam is a mild off-road cam, and its specs are within the parameters of the Holley stock configuration, so we didn’t need to change anything. If we had a bigger camshaft, then there are check boxes in the menu that would have made the correct programming.”

It took less than 10 minutes for Dunks to fire up the engine from the time he plugged his laptop into the Holley ECM, and it was his first time using the Holley LS1 EFI wiring kit. “This is a nice wiring package for the do-it-yourselfer. It’s simple and easy to understand. At the same time, if you’re a seasoned tuner and want to do a lot more in-depth stuff, it has all the capabilities to edit the parameters for any tune needed.”

Finishing Touches

Like with any engine swap, there are a lot of small details that need to be addressed before this TJ hits the trails. We ditched the stock TJ dash cluster for an Auto Meter gauge cluster, but we still have to finish connecting the A/C hoses, and we’re waiting for the LS1/TH400 locking dipstick to arrive from Goat Built (the stock GM dipstick tube doesn’t work in this setup).

The exhaust and driveshafts will be easy to hook up. We know what cable shifter we want to run with the transmission, but we haven’t decided on whether or not to make mods to the stock TJ center console, make a custom console, or just mount the Atlas 2 sticks and shifter flat on the Jeep’s floor. Those will all be handled in due time.

For now, we accomplished what we set out to do: swap out the 4.0L for a dependable, strong-running EFI GM V-8 and minimize time and money on the engine swap. In the process, as is common with most mods of this type, we splurged here and there to make the total package even more bulletproof for our particular off-road needs and interests. We hope some of what we learned will be helpful should you take your rig in the same direction.