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CHAPTER 3

ENGINE SWAPS

Some people can’t leave anything alone and Jeep owners have been swapping engines into their Jeeps since the earliest CJ. Engine swapping has reached a level of sophistication that allows even a relative novice to swap an engine into a CJ with great success. Engine swapping is one of the more popular topics resulting in questions and research by Jeep owners. There are no real limits to the swaps, but there are ones that make most sense, from the ease of installation to the cost of the project. Swapping an engine can snowball into a major project with major expenses, and problems can grow to the point that they can only be resolved with expensive solutions.

Swapping a Chevy small-block into a CJ is by far the most popular swap and has been a project since the earliest CJs. This circa-1980s father and son engine swap resulted in an overpowered and terrifying but fun-to-drive Jeep for my father and me. Aftermarket support for this swap is so great that a Jeep owner can swap in an engine during a weekend with proper parts.

Luckily for 1972–1986 Jeep owners, AMC lengthened the CJ by 3 inches at the rear of the front fenders/hood area. These extra 3 inches allowed AMC to squeeze in the I-6 and 304 V-8, but more important, those extra 3 inches made a world of difference to the art of the engine swap.

A Jeep owner using the logic “I had this engine laying around” as a starting point for the swap usually ends up in a bad situation with a negatively impacted wallet. It is usually recommended to choose a swap candidate based upon what you want to do with your Jeep, research the details of the swap, plan the swap, and do it right. Swaps are not really for the mechanically challenged or inexperienced DIY types. It is so much more than just bolting in an engine and hitting the key. The little details, such as exhaust, fuel lines, cooling, and clearance, are just the tip of the iceberg.

Because the goal here is to build a Jeep that works well on- and off-road, the engine you swap in should provide plenty of low-end torque, good highway driving power, efficient fuel mileage (realizing this thing is still a Jeep), and some extra power just for the heck of it. The swapped engine should match the driveline, including all components such as the transmission, transfer case, and axles. In addition, the engine swap shouldn’t cost a fortune or add a level of complexity to cause potential problems and/or failures. A finicky engine on the trail in the middle of nowhere can ruin anyone’s day.

AMC-era CJs had an extra 3 inches added to the rear of the front clip, increasing the frame, hood, and fender length. Those extra few inches at the bottom of the front flare allowed physically larger engines to fit in the Jeep’s engine compartment.

A souvenir gained from the result of a swapped engine with a little too much horsepower and a young Jeep fan with a lead foot. These Dana 44 spider gears with sheared and broken teeth plus the not-shown repair bill and destroyed ring and pinion are a testament to the need for a well-thought-out engine swap.

In general, having access to the donor vehicle or all the components that made up the engine of the donor vehicle eases the swap and saves hours of parts searching. Missing components, including brackets, alternator, wiring, etc., slow the installation and end up adding to expenses. Swapping modern fuel-injected engines drastically improves the Jeep’s drivability both on- and off-road, but these swaps are complex and carry even more importance to gather all the components before beginning. Take lots of pictures of the donor vehicle, take notes, and label stuff.

This book isn’t big enough to be a comprehensive guide to swapping engines. It’s a broad topic with many variables and options. Tried and true usually results in the best, most reliable swaps for both those new to swapping engines and the experienced. Exotic and strange conversions are best left for the seasoned and deranged Jeep enthusiasts.

You have two choices when swapping an engine into a Jeep: factory and non-factory. Both have advantages and disadvantages, such as larger aftermarket support, ease of replacement parts, and total cost of the swap. Consideration of both options should be thought out before beginning the project, and be careful of the outlying items that escalate the difficulty and expense.

Factory Swap Overview

Swapping a factory Jeep engine into another Jeep is the easiest swap to make. There is a special feeling of satisfaction with just removing the 4-cylinder engine and staring at the empty engine bay. Most swaps can use factory components and take little or no guesswork as to what fits. Swapping a factory engine usually comes in several forms: swapping a factory 4-cylinder with a factory I-6 or V-8, swapping a factory I-6 with a V-8, swapping a factory I-6 with a bigger factory I-6, and swapping a factory V-8 with a bigger factory V-8.

As stated earlier, having access to the donor Jeep makes the job much easier. Items such as engine mounts, radiators, throttle cables, and brackets can be potentially difficult and expensive to locate later.

If the original transmission is to be retained, most factory engines bolt to the transmission by using the donor engine’s factory bellhousing. Much of the factory wiring is usable with some minor modifications. Factory engine mounts specific to the particular engine being swapped should bolt directly to the Jeep’s frame. As with the engine mounts, radiators bolt in and hoses can be readily obtained from parts dealers.

This 1980s CJ is still running the factory AMC 4-cylinder engine. The fan shroud extends several inches from the radiator to meet the little 150-ci engine. Anyone with experience driving a late-model CJ with a 4-cylinder understands why adapters exist.

Replacing a tired 304 with a rebuilt AMC 360 is just the trick in this CJ-5, which runs an Edelbrock Performer camshaft and manifold topped off with a Holley Truck Avenger 4-barrel carburetor. The smooth operation of the V-8 with its low-end torque has made this combination a favorite.

Engine mounts, among other items, degrade over time and should be inspected and replaced if needed during a swap. Polyurethane mounts are a popular replacement for the factory-style rubber mounts.

To Swap or Not

The highly popular Chevy small-block V-8 swaps can result in a Jeep with a reliable powerplant with proper power and that cool V-8 sound. Some swaps can have a high-horsepower engine with a lopey cam that sounds wonderful and scares the wits out of you; others have more reasonable daily-driver V-8s that are perfect for a CJ. Similar results from other make engines can be found. If this sounds good, you should also consider the added work and expense that follows a swap to a non-factory engine.

It’s well known that the AMC V-8 can’t match the aftermarket performance parts availability and the less expensive prices that separate the same part from the two manufacturers. For example, an Edelbrock Performer manifold for a small-block Chevy is about 40 percent cheaper than the same manifold for an AMC. This difference can accumulate when adding performance parts to an AMC V-8, but the price of adapters and the complexity of a swap often wash it away.

In addition, it’s very convenient to be able to walk into an automotive parts store and get a part for an AMC V-8 or I-6 CJ. Fan belts, hoses, alternators, starters, etc., are simple to obtain without the guesswork encountered with other swaps. Try explaining to the teen at the counter of your local parts store that your Jeep has a Chevy 350.

Perhaps as AMC replacement parts and engines become harder and more expensive to find, swapping may be a necessary and more cost-effective solution. For now, though, sticking with AMC for the kind of Jeep you are building provides for the simplest, least expense project. ■

Swapping a Chevy small-block into a CJ is by far the most popular non-factory swap, and a balanced-power engine results in good performance on- and off-road. This CJ has a later-model Chevy V-8 (indicated by the center bolt valvecovers) running a Holley 600 4-barrel carburetor and fenderwell headers.

A factory swap offers a fair amount of ease compared to swapping a non-factory engine. This crate AMC 360 is taking the place of an I-6 in this 1984 CJ-7. Using factory-style motor mounts, radiator, hoses, and more is possible with a Jeep-to-Jeep swap. After a short time mated to the factory transmission, a TF727 automatic was swapped in for strength and drivability.

Consider replacing some possibly old and worn items when swapping a factory engine. Throttle cables, engine mounts, radiators, and other general tune-up items may benefit the Jeep by being replaced. Old engine mounts tend to get brittle or separate completely. Aftermarket replacement and upgraded solid mounts are readily available. Replace any worn-out or brittle wiring with proper-size wire, perhaps even adding a secondary circuit block to distribute the power load better and make the wiring safer.

Non-Factory Swap Overview

There is technically no limit to what engine can be swapped into a Jeep, but most swaps just don’t make sense from both practical and budget points of view. Novak Conversions in Cache Valley, Utah, is probably the best-known expert shop for Jeep engine, transmission, and transfer case swaps and conversions. Due to the vast amount of information about non-factory swaps, some high-level discussion is all there is space for within this chapter. Consider researching your conversion by starting with Novak and the many online Jeep websites and tech forums.

For the inexperienced, a swap may seem simple. However, a snowball effect often occurs when the list of incompatible components grows. The following items are just the obvious components that a swap can potentially impact.

Radiator

Most V-8 swaps require a highercapacity radiator to properly cool the engine and to match up to the inlet/outlet ports on the engine. A Jeep that sees trail use puts extra stress on the cooling system because of the continual slow speeds often experienced. Using a good fan, electric or engine driven, and fan shroud in addition to the proper radiator ensures that the Jeep stays cool. The small grille opening and narrow radiator space limits the radiator size; often three- and four-core radiators are used. A few companies make bolt-in swap radiators that are properly set up for the Jeep and provide proper cooling.

Electric fans can pull a large volume of air to keep the Jeep’s engine cool; aftermarket support created the availability of bolt-in dual fans that include a proper-size shroud. Electric fans should be controlled by a thermostat and mounted to the rear of the radiator.

In recent years swap radiators are all-aluminum cross-flow styles, replacing the older copper/bronze construction, providing extra cooling power and good looks. Novak’s KryoFlow HD radiators are properly sized cross-flow aluminum versions that are a direct bolt-in, designed to match the port needs of a swapped engine. Cooling problems are not something to take lightly and “going cheap” here usually has costly or big hassle results.

Mounts

Mounting the donor engine is likely the first big step in the installation. Locating the engine is often accomplished either by matching the engine to the original transmission location or by ensuring front (radiator) and rear (firewall) engine clearance. Altering the engine location that requires the transmission/transfer case to be moved requires modifications to the transmission mount or skid plate. Typically, a Jeep engine is mounted slightly offset to the driver’s side to make room for the front driveshaft and differential.