This modified I-6 provides loads of low-end torque perfect for both on- and off-road driving. The simple setup is easy to maintain and repair, if needed. Specs for the engine include a 258-ci I-6, Clifford manifold and header, Howell TBI, TFI ignition conversion, and Omix-ADA valvecover.
An AMC V-8 has no problem powering a CJ and performance modifications always add to the package. This factory-304-equipped CJ-7 runs that Edelbrock Performer Series combination that works so well. The Holley carb, intake, and cam combination result in extra-low-end torque and mid-range horsepower, which are well suited for an on- and off-road Jeep. The in-frame Hedman headers, dual exhaust, and HEI distributor finish the engine.
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