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To Engine Swap, Or Not To Engine Swap?

The Jeep Grand Wagoneer—built between 1984 to 1991 by the tag-team mix of AMC and Chrysler, and based on the long-standing SJ platform that dated back to the brand's Kaiser years in the early 1960s—is an icon in the SUV world. Known for its rugged chassis, comfortable ride and respectable off-road chops, the stylish Grand Wagoneer represents a bygone era in truck design where wood veneer and Brooks Stevens-penned greenhouses dominated showrooms.

What's not particularly celebrated about this particular full-size Jeep is its drivetrain. Featuring a carbureted 5.9-liter V8 that produces a genteel 140-ish horsepower and 280 lb-ft of torque, backed by a 3-speed 727 automatic transmission, the Grand Wagoneer's forward progress might best be described as 'glacial.'

1987 Jeep Grand Wagoneer

How would I know? I picked up a 1987 Jeep Grand Wagoneer as a project earlier this year. My particular example features an exceptionally rust-free body (a rarity in the northeastern part of the continent), a fairly functional set of features (including ice-cold AC) and a version of the 360 cubic inch engine that runs quite well.

Unfortunately, in addition to being slow as molasses, my Jeep also happens to deliver an astounding 6 miles per gallon regardless of how I happen to drive the vehicle. Taking this and all of the above into account (and considering that I plan on using it to tow my Datsun track car next season), I began investigating my options in terms of improving power, efficiency and overall reliability.

This lead me to a very distinct fork in the road. You see, to fix what the factory has wrought under my hood, there are only two real options: update AMC's original iron, or swap in something much more modern. I spent the entire summer debating the merits of each choice before coming to a decision.

It's Only Original Once

I grew up around classic cars, and as such I have a healthy respect for the arguments for originality when maintaining a survivor like my Jeep. Indeed, 'survivor' is the best word to describe the Grand Wagoneer parked in my driveway, with its patinaed paint, lack of aftermarket modifications and black cat Marchal fog lights dealer-installed on the front bumper.

1987 Jeep Grand Wagoneer

That being said, originality is a moving target when discussing a vehicle built on the SJ chassis. Given that AMC had spent years wandering the financial wilderness prior to producing the Grand Wagoneer, and would change ownership more than once in the interim, Jeeps of the era tend to be a mash-up of gear from a variety of automakers. Whatever AMC could afford to stuff inside its full-size hauler was what you got, which meant Ford, GM, Chrysler and even Renault had a hand in contributing parts to the vehicle.

1987 Jeep Grand Wagoneer engine.

It might be understandable, then, that not all of these components are of the highest quality, nor necessarily do they play nicely together. If your priority is to own a museum-quality, 100-percent original Jeep then you might want to hew to the 'factory' offerings for your given model year, but if you plan to actually drive your Grand Wagoneer on a semi-regular basis you're going to be making reliability modifications that will shake out some of its original (read: terrible) parts.

With that argument out of the way, to my mind 'keeping it original' meant preserving the numbers-matching AMC 360 and doing my utmost to introduce more power and better efficiency into the equation. Research down this path lead me to a few conclusions:

• Swapping in a new intake, exhaust, carburetor and ignition system was a proven route to more power, but not necessarily reduced fuel consumption.
• Moving to an aftermarket fuel injection system, in addition to most of the mods listed above, had the potential to provide a moderate mileage boost.
• Removing the emissions equipment choking the motor was a necessity.
• The 727 transmission's lack of an overdrive gear would continue to haunt me, likely necessitating a swap here in any case.
• The AMC 360 was a fickle beast.

Let me explain that last point. During my research into building the 5.9-liter motor I encountered numerous owners who experienced engine failures a few thousand miles after a complete rebuild—or who upgraded their ignition and fuel delivery systems only to have some other engine component fail and leave them stranded.

1987 Jeep Grand Wagoneer engine.

This drove home the fact that my Jeep's power plant was a 30-year-old design even when it was brand new, and we're now another 30 years past its on-sale date. With 125,000 miles on my vehicle, I was courting disaster nearly every time I turned the key. Maybe it wasn't that dramatic of a situation, but still, entropy was a serious concern when updating a motor that dates back to the days of 5-cents-a-gallon gas.

Then there were the costs involved. The above upgrades weren't all that inexpensive, given that the market for AMC engine hop-ups is fairly niche. Sticking with a carburetor wouldn't provide me with the reliability I was looking for, either, especially not towing through the mountains on a hot summer day, so that meant fuel injection would be necessary. This further shifted the costs onto the higher side of the scale—and in the end, unless I did a full rebuild, I'd be dumping significant cash into a high-mileage engine that was never intended to push out more than a couple of hundred horsepower in the first place.

The Dark Side

With its generously-proportioned engine bay and complete lack of electronic drivetrain controls, the Grand Wagoneer is a perfect candidate for almost any swap you might want to attempt. Indeed, even from the factory Jeep wasn't too shy about using someone else's engines, tagging in Buick's 5.7-liter mill for a period in the late 1960s.

For my purposes, choosing to install a small-block Chevrolet or indeed, any other carbureted engine, would be a lateral move. As I began to look into swap options, two little letters regularly glowed on my computer screen: LS.

While it might seem like sacrilege to install a GM motor in a Jeep, keep in mind that back in the Kaiser days this was a regular occurrence. It's also helpful to understand that logic behind the LS suggestion, as these motors are among the most popular swap choices across a startling number of projects for very good reasons. They are relatively lightweight, simple to install and provide a good mix of power and efficiency, all in a modern package.

LS1 Engine.

I did look into a number of different choices, including a modern Mopar motor (such as the 5.7 Hemi V8), Cummins diesel swaps, and even Ford Coyote options. In the end, none had the packaging nor the incredible aftermarket swap support of the LS in the full-size Jeep platform. In fact, a veritable cottage industry has sprung up around the LS-Jeep formula, with companies such as Novak, Flop Shop and BJ's Off-Road all offering packages—some quite comprehensive—for performing the transplant.

The most important take-aways from my swap research were the following:

• The most plentiful, and affordable, LS engine out there—the 5.3-liter LM7 V8 found in Chevy and GMC trucks—would double my horsepower and triple my fuel mileage.
• The LQ4 6.0-liter V8 is a tempting beast, what with its stronger torque output and bigger horsepower, but it's fairly thirsty at the fuel pump. A tune and headers on an LM7 can put you in LQ4 territory real quick.
• Adapters for the existing four-wheel drive transfer case in my Grand Wagoneer are available, but it's much cheaper to bolt in a GM-sourced manual T-case instead.
• Wiring for the swap is relatively simple, but making every gauge work like it should is a bit of a hassle.
• Every LM7 comes with an overdrive transmission, which means I can go to a more aggressive rear gear.

1987 Jeep Grand Wagoneer

Finally, there's the question of cost. Would it surprise you to learn that the cash required to replace my AMC 360 with a Chevrolet-sourced LS were nearly identical to that needed to build the original motor? When viewed from an economic perspective alone, it becomes almost impossible to defend dropping dollars on rebuilding an engine that was never intended to offer big horsepower, instead of moving over to a simple, modern and easy-to-maintain drivetrain.

Heart Transplant, Here We Come

The decision to go with an LS swap in my Grand Wagon was not a quick, nor an easy one. I let the facts percolate in the back of my mind all summer long while I drove the Jeep as often as I could. Strange as it might sound, the more time I spent with the vehicle, and the more of its character I came to admire, the greater the impulse became to move to a newer engine.

1987 Jeep Grand Wagoneer

The reason? I'm so enamored with my Jeep that I want to drive it as often as possible, and currently, I don't trust it nearly enough from a reliability standpoint to take it on longer excursions—and certainly can't tow with it. Rather than roll the dice on a rebuild, I'm going to follow the hundreds of other Grand Wagoneer owners who modernized their rides and never looked back. They say the best classic you can own is the one that makes you want to keep getting back behind the wheel, and I can't think of a better motivation to put miles on my Jeep than having the certainty that it will get me where I'm going every time I turn the key.

Click here to find out what makes the Jeep Grand Wagoneer the ultimate restomod.

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