An examination of all of the years of the CJ will conclude that the 1978 and 1979 CJ-5 and CJ-7 were the epitome of the CJ. These two years offered a V-8, strong reliable transmissions such as the T18 and GM TH400 automatic, large front disc brakes, and 11-inch rear drum brakes. One little exception to this is the somewhat rare 1980 CJ-7 with a V-8 and an automatic. This combination included the Chrysler TorqueFlite automatic (TF999) and a Dana 300 transfer case, a formidable off-road package.
Putting It All Together
In truth, any year and any model CJ makes a perfect Jeep for on- and off-road use. Even a stock CJ is a blast to drive off-road and is very capable. In the following chapters, building and modifying a CJ from top to bottom for maximizing performance on- and off-road is discussed in depth. Jeep owners tend to tinker with their Jeeps continuously. From engine modifications, lift kits, lockers, and more, it’s common for CJs to see many changes and phases. Not surprisingly, CJs still remain a favorite Jeep for many, even with modern Wranglers everywhere.
Considered the best years of the CJ, the 1978 and 1979 CJs offered strong I-6 and V-8 engines, tough transmissions, and usable gear ratios. After 1980, the CJ became less off-road friendly out of the box due to fuel mileage and exhaust emissions requirements.
A small number of 1980 CJs were available with a 304 V-8 until the 304 was discontinued. This, combined with the newer Chrysler automatic and Dana 300 transfer case, made this Jeep extra special and extra rare. This 1980 CJ-7 is perfectly modified to perform well both on- and off-road.
CHAPTER 2
ENGINE
Engine performance modifications in the Jeep community are rather different from most other forms of automotive enthusiast engine modifications. A Jeep engine is most often modified to provide increased low-end torque rather than increased high-end horsepower because the needs of the trail are different from those of the dragstrip. Jeep engines tend to run at slow speeds and slow vehicle movement on the trail, which puts extra stress on the cooling system. High-compression, high-horsepower engines usually do not tolerate the kind of driving conditions Jeep owners might expose their Jeeps to.
This 1977 CJ-7 was a factory V-8 equipped Jeep with a TH400 automatic and Quadra-Trac transfer case. Of all the modifications, upgrades, and enhancements, the V-8 has remained stable with just enough performance modifications to perform well on- and off-road.
Even though the CJ series was discontinued years ago, it is possible that local and federal emissions laws are still applicable. Research into emissions laws should be done before digging into modifying your Jeep’s engine to avoid violating laws and rules, which could result in the inability to pass a smog test. Many aftermarket parts are smog legal and many do not alter emissions systems at all. Typically, swapping an engine of a newer model year is permissible by emissions laws, as long as comparable emissions equipment is retained. With the advanced age of the AMC-era CJ, it’s hard to imagine swapping an older model year engine into the Jeep.
Factory Engines
Factory Jeep engines were briefly discussed in Chapter 1, so here I dig more into “actually useable” Jeep engines, including the advantages and disadvantages of each. Two 4-cylinder engines were offered in the CJ during the AMC era. Although both were functional engines, their lack of power and torque make them poor choices in a modified CJ, so they should be avoided and/or swapped. In the following few paragraphs, I discuss the I-6 and V-8.
AMC I-6
The 232 and 258 I-6 engines are similar in design and use many of the same components. The 258 was a far more popular engine in the AMC-era CJ than the 232. The engine is well known as reliable and provided a significant amount of torque for its size, thanks to its long compression stroke. The 258 has proven itself as a workhorse engine in a CJ and can provide years of reliable service to its owner. The low-end torque of this engine and the low gears of a CJ is a near-perfect combination. However, there are some gotchas with this engine, and perhaps the biggest one deals with the horrific carburetor system found on 1981 and later CJs.
The AMC In-line 6-cylinder powered the CJ and so many other Jeep vehicles reliably and effectively for more than 30 years. This Jeep’s 258 is showing its age and use from all the years of mud, grime, and dirt present on it. These engines were true workhorses that were capable of 250,000 miles from brand new to totally abused.
AMC V-8
The AMC 304 V-8 is a fun engine for a CJ and even in totally stock form can provide plenty of power and torque to throw a CJ around on the street and trail. Although the 1970s smog-laden V-8s weren’t known for their performance, with a little help they can come alive. AMC V-8 engines were popular in the AMC muscle cars they came in, such as the Javelin and AMX. Thanks to those cars, a space was created in the performance aftermarket for the AMC V-8, and many upgrades and modifications are available. V-8–powered CJs running fenderwell headers and glasspack mufflers are an icon of the late 1970s.
The AMC Tall Deck V-8 engines were often accused of being copies of other manufacturers’ engines when in reality the engine was its own creation. The thing that separates the Jeep from other types of automotive enthusiast crowds is that a dirty, muddy engine is considered more attractive than shiny parts. Evidence that the Jeep is used the way it is intended only makes onlookers more interested.
Modify, Rebuild or Swap?
Before modifying your factory Jeep engine, consider its condition. Is it worth modifying, is it too far gone and not worth rebuilding, or even further swapping? Some inspection and a few tests should be performed on your Jeep’s engine before making this decision. A good-condition engine that is ready to modify should stand up to the added performance from the modifications. A rebuild candidate may be a fair-running engine but due to maintenance neglect or excess wear, this engine would benefit from a rebuild, along with modifications. A freshly rebuilt engine can be as good as new and can revitalize a Jeep. In the case that the engine may cost too much to rebuild or is beyond rebuildable condition, a replacement or swap should be considered.
Inspection and Testing
An engine in running condition is a good start, but how well it runs and how well it was maintained are just a couple of items that need further examination. Starting on the outside, inspect the cleanliness of the engine. Excess grease and gunk on the outside of the engine can mean there were unfixed leaks from old gaskets or worse, cracks. This grime hides problems and can cause the engine to run hot or possibly even catch fire. This book doesn’t focus on the specifics of rebuilding engines; consult an appropriate guide specific to your engine for more detail.
Finding grime like this inside your engine may mean a rebuild is in order. Grime in the rocker arm area usually means it’s everywhere. Changing oil and filter according the manufacturer’s specifications prevents this, even on an old engine. Complete disassembly and professional cleaning is the only real way of removing the contamination.
Compression
Compression testing can indicate