The Novak Guide to
Installing Chevrolet & GM Engines
Jeep CJ Universals, 1980-1986
There is hardly a powertrain conversion more exciting, enjoyable, beneficial and well-documented as with these, the last era of the CJ Series Jeeps. Individuals are swapping for reasons as varied as the uses of the Jeeps themselves, and the results are invariably among the greatest of improvements owners will make. The move to a cleaner, stronger, reliable, efficient, serviceable GM engine (typically Chevrolet) is one that makes its own good case.
A Little History
A "little" history is a difficult thing when discussing the Jeep CJ, but essentially, the CJ's of the 1980-1986 era were nearly identical to the CJ's of the 1974-1979 era. Based heavily still on the Bantam/Willys/Ford military Universal, these CJ's feature a compact design; narrow track and short wheelbase for weaving up, through and around obstacles.
Sales were still strong for AMC's stalwart CJ and they were outfitted with a variety of options for buyers. The rest of the pertinent history is largely mechanical, as discussed below.
For 1980, the AMC 258 I6 was now the largest engine available in the CJ platform. AMC left behind the thirsty AMC V8s formerly available, as fuel economy standards and increasingly complicated emissions controls took their tolls.
And, new for 1980 was a four-cylinder, not seen in the Jeep CJ since 1971. This time around, it would be the GM 151 CID "Iron Duke". This engine remained available through 1981. However, AMC had it in use just as a stop-gap, and in 1982 they released an entirely new I4 engine. This was the AMC 2.5L, carbureted four-cylinder with 105 hp. Both engines were offered with fuel economy in mind, but they both were comparatively meager in their output; a four-cylinder in a quarter-ton truck is just that, and the efficiency and longevity problems with operating their engines past their abilities has been fully experienced by too many for too long.
Little argument need be made about why an individual with one of these smaller engines in their Jeep may feel the impetus to upgrade.
As for the 258, it was always a good motor, though never wholly exciting due to core design drawbacks, including those of long-stroking I6 and the effects that has on power and economy, vis a vis the broader revving power ranges achieved by other fundamentally different platforms like the V6's & V8's.
It might be said that the 1980's did not treat Jeep very well in transmissions. Transmissions for the 1980 and later CJs were all new, comprising:
- The Borg Warner SR4 Transmission was the base four-speed available with both the 151 and 258 engines through 1981. This light-duty transmission was short lived, in durability and production. In 1982, Jeep introduced the Borg Warner T4 & T5 Transmissions. respectively four and five-speed gearboxes, the latter featuring an overdriven final gear.
The above transmissions are not appropriate to retain in a V6 or V8 conversion. Novak made a bellhousing adapter for them for a short time,
but the futility of adapting an engine to a gearbox that just would not last became self-explanatory. Because of these transmissions' weak service records behind stock Jeep powerplants, we do not offer any conversion to V6 or V8 power. This is essentially a small car transmission in a truck. The customer's time and efforts are best spent converting to a stronger transmission.
- A factory option available with the 258 I6 was the Tremec T176 Transmission. rated as medium-duty. Though a rarer option, individuals with this transmission available may retain it in their conversion. Our #G176 adapter assembly allows the adaptation of a conventional Chevy and other GM bellhousings to the T176. An even rarer option than the T176 was the TorqueFlite 999 as introduced in the CJ in 1982 with the 258. This transmission evidenced AMC's increasing courtship of Chrysler. The transmission was similar to previous 999's but had a dedicated case for the 258's bolt-pattern and a 4wd tailhousing.
New for 1980 was a history making transfer case, provided by Dana Spicer as had been its Dana 18 & Dana 20 predecessors since 1941. The pinnacle of quality, gear-to-gear transfer cases was reached with the advent of this Dana 300. The Model 300 was, by a long shot, the strongest link in the Jeep powertrain chain in the 1980 through 1986 CJ's. The most successful conversions retain the gear-driven Dana 300 due to its strength, compact design, refined operation and serviceability. More on this later.
Planning the Powertrain Conversion
It is crucial to discuss transmissions early on. They are sometimes more central to the conversion than the engine.
In the entire production run of these last CJ Jeeps, all transmissions except one should be ruled out when performing a GM engine swap. The SR4, T4 & T5 transmissions were hardly durable behind the lackluster factory engines. GM power can spell their demise within days to months. Though the 999 automatic available with these Jeeps is a more durable automatic, its strength and features are so far eclipsed by the GM HydraMatic variants (discussed below), that we do not offer an adapter for its retention in a GM engine upgrade. The T176 manual transmission, however, can be successfully retained in a GM engine conversion. Details, below.
Though some of these following transmissions do not offer overdrive, many CJ Jeeps with larger tire sizes and proper axle ratios will still allow for a respectable freeway cruising RPM. An individual is best to perform some gearing calculations as part of this stage of the planning.
Automatic Transmission Options
Many CJ swaps are likely destined to have automatic transmissions. As discussed above, the 999 is not really a good option.
No adapters are generally needed to marry the following GM automatic transmissions to their usually matching Chevrolet engines.
TH350. Swappers should surely consider the GM TH350 automatic. The Turbo 350 is strong, compact, widely available and affordable to buy, service and build.
•The Dana 300 is adaptable to the TH350 with our #135 series adapter kits .Source: www.novak-adapt.com