Few modifications can make a bigger difference to the power, torque, and fuel mileage derived from your engine than changing the camshaft. The 4.0L in our '89 Jeep Cherokee had 130,000 miles on the clock, but the venerable six-cylinder engine was still running strong with good compression. All hot-rod owners will tell you a camshaft change really perks up any V-8, but we wondered how a peppier cam would work on the inline-six. After speaking with the tech line folks at COMP Cams, we decided to give the Xtreme 4x4 camshaft (PN 68-232-4) a shot. The increased lift and duration would provide a denser charge into the combustion chamber and, hopefully, result in a more powerful engine. We wanted to enhance the power low in the rpm range. In addition, we knew it would be compatible with the factory fuel injection system. This camshaft would also respond well to an exhaust upgrade if we decided to do so in the future.
Sliding a new camshaft into your engine may seem like a big deal, but it is really easy for any semi-competent weekend off-road enthusiast. However, on a 4.0L engine, the camshaft is positioned in the block and requires removal of the cylinder head, radiator, and several of the front engine accessories. In general, for a first-time installer, a camshaft swap on a 4.0L engine should take the better part of the day with the proper service manual. If you are confused about how to properly install your camshaft, call the COMP Cams tech line.
A stop by Westech Performance with our Cherokee netted a fairly weak but not surprising performance. Peak horsepower was a poor 92.8hp at the tire and torque was barely able to reach the 147 lb-ft mark. Next stop was Bitetto Motorsports where Vince Bitetto installed the cam.
It seems like a lot of work, but the camshaft finally emerges from our engine. Using a long bolt in the end of the camshaft is helpful in leveraging its removal. Avoid banging the camshaft around when pulling it from the engine or you could damage the cam bearings inside the engine. Install the new cam and lifters and put the engine back together as per your service manual. | 
Our '89 Jeep Cherokee came to us with a cracked head, but Bitetto found a new head and had it back on the road in time for our test. Despite 130,000 miles on the odometer, a compression check revealed that the engine was sound and a great test bed for our | 
As with most underhood engine projects, the first thing you do is disconnect the battery cables. In our case, to achieve enough room, we removed the entire battery but left |
You'll also have to remove the distributor and most of the components in front of the engine, including the cooling fan(s), belts, fan shroud, tranny cooler (if equipped), radiator, and grille. You should be able to maneuver the A/C condenser aside without disconnecting the hoses and releasing the pressure. There needs to be enough clearance to slide the long camshaft out the front of the block. | 
Pull the valve cover and remove the rocker arms. Note, on this engine there is no rocker lash adjustment other than differing pushrod or valve stem lengths. The rockers only go on one way and are torqued in place when reinstalled. Very simple. | 
Rocker arms and pushrods wear in a specific way unique to their position. They should be returned to the engine in the same position they came out. Keep them in order to remember their position for reinstallation. Inspect them for damage and clean them before |
Unlike a V-8, you'll need to pull the head to swap the cam on a 4.0L. Replacing the head bolts is not a bad idea if your engine has seen more than 100,000 miles like ours. Lifting off the head can be a struggle, especially when removed with the intake and exhaust manifolds. This total unit weighs around 110 pounds. An engine hoist makes the process much easier. | 
Using a magnet, you can pull the 12 lifters from their bores and discard them. New COMP Cams lifters are slathered with assembly lube and installed in their place once the new cam is installed. | 
The idler pulley, crank pulley, timing-chain cover, timing chain, and timing sprockets are last to come off before |