Jeep Conversion Engine
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The following information is not meant to be exhuastive of each engine, but only instructive as to which motors have the best histories as Jeep conversion engines. We hope it will be valuable to your planning process.
We've listed engines in general order of popularity, determined by customers' correspondance and order history.
Chevrolet Small Block V8, Generation I-II, 1955-1998+ (265-400, LT1, etc.)
The 1955-2001 Chevy Generation I & II Small Block V8's are very popular for Jeep swaps. Stock Small Block series engines consist of the following displacements: 265, 283, 305, 307, 327, 350, 400. Some of the reasons for the popularity of these engines are: availability, outstanding parts interchangeability, compactness and light weight, plus the fact that these engines fit nicely in most Jeeps. These engines have been popular choices since the mid-sixties, and because they are so familiar, the information and parts required to swap them are more widely available than with any other motor.
The Generation III+ engines are creeping quickly up on the classic Small Block in popularity. However, the Chevy V8 is essentially immortal in reputation and implementation.
GM Small Block V8, Generation III, 1997-2007+ (LSx, Vortec, etc.)
The rise in poularity of the GM Generation III+ Small Block V8's has been meteoric. They feature tremendous power, efficiency, clean-burning, and well supported computer and wiring systems. Like their Small Block predecessors, the Gen. III+ family features availability, outstanding parts interchangeability, compactness and light weight, plus the fact that these engines fit nicely in most Jeeps. We expect them to surpass the Chevrolet Small Block in frequency of conversion before the end of this decade.
Chevrolet Small Block V6, Generation I-III, 1978-2007+ (200-262, 4.3L, etc.)
The Chevy 200, 229 CID and 4.3L V6 are outstanding motors. These engines are essentially a truncated Chevy V8. They make for great Jeep engines. Like the Small Block V8, the 4.3 features excellent advancements through its production span. This motor is being put into Jeeps with frequency due to its size, power, economy and weight. Modern incarnations include the Vortec V6's, which offer unusal torque for a V6 and a neat powertrain control system, in the vein of modern GM powerplants.
The Vortec V6, while short enough to fit into early "low-hood" Jeeps, is too tall for proper fit unless one is willing to do a 3/4" to 1" body lift and possibly modify the 4.3L air intake arrangement. Alternatively for these CJ2, CJ3 and M38 Jeeps, we recommend earlier versions of the Chevy V8, Chevy V6, the Buick V6 or the Ford I4.
Ford Windsor Small Block V8, 1964-1996 (289-351, 5.0L-5.7L, etc.)
The Small Block Ford "Windsor" V8 can be installed in many Jeeps. The Ford Windors are the 260, 289, 302 and 351W. This engine is longer than the Chevy V8, which is an installation challenge CJ's up through 1971. Ford enthusiasts who know these motors and their parts interchange information well, swear by them and install them with good success. They are most popular in the 1972-1995 CJ Universals and YJ Wranglers, and for good reasons. The general lack of OBD-II versions of this motor have discouraged their swaps into TJ & JK Wranglers.
In 1997, Ford left the Windsor behind (in production vehicles, anyway) for its new family of Modular engines, which have not caught on for Jeep conversions.
Buick 90 Degree V6, 1965-1986 (225-252)
A very popular engine for 1972 and earlier Jeep CJ swaps is the Buick V6 as used by all GM divisions. The 1966-71 225 CID was optional in CJ5's of those years. After Buick bought the tooling back from Jeep, the engine was reintroduced in 1975 in GM cars as the 231 CID V6. This was the same as the 225 except for .050 larger bore. In mid-1977 the 231 got a different crankshaft, camshaft, distributor and flywheel, which made it an "even fire" engine. This became the 231 and similar 252 V6. These V6's have some great benefits. Though usually adequate in their stock form, they can be built for excellent torque and outstanding horsepower. These V6's work best in Jeeps weighing less than 3,000 pounds.
Chevrolet Big Block V8, 1965-2007+ (409-454, 7.4L, 8.1L, etc.)
Chevrolet Big Block V8 engines are fantastic engines, but best relegated to wide-frame Jeeps like the FSJ and YJ. With the Small Block V8 and Gen. III+ motors developing such adequate power, having lighter weights and more compact envelopes, one should reallly only choose a Big Block for severe service and ground-splitting power.
Mopar Small Block V8 (318, 360)
The Dodge Small Block 318 and 360 V8's are the best Mopar swaps into Jeeps. These engines are strong, reliable and affordably maintained. They are roughly the size of the Chevrolet Small Block. As Jeep has come under the wing of Chrysler, some are interested in installing these engines in their Jeeps. However, it should not be assumed that becuase Jeep and Chrysler are joined, that it makes their swap any easier or less expensive. Mopar PCM computers (applicable to the more modern Magnum series) are notoriously tricky to program, with very few establishments peforming this service. Chevrolet, GM and Ford Small Block conversions remain far dominant.
Jeep / AMC I6 (232, 258, 4.0L)
The AMC / Jeep I6 conversion is a less intuitive swap than most individuals assume when planning a swap, and the surprises often weigh down the project, discouragingly. The Jeep I6 has evolved through the years, and with the advent of the newer 4.0L, they are in their best incarnation. However, they've yet to acheive the efficiency and wide torque band that many V6's and V8's offer. A 4.0 swap can be an upgrade from a factory I4 or carbureted 258, but for all of the work, expense and 2/3 the power (and excitement) of a V8, they may not be the best solution. They sometimes present some difficult computer reprogram situations, with very few Chrysler techs willing to recode them for any kind of conversion.
Individuals do stroke and supercharge these motors for more performance, but the costs and work of these procedures are consistently more expensive than a modern V8 conversion. Our customers that have discussed them with us have claimed better satisfaction with their V8 upgrades.
Jeep / AMC V8 (304-401)
AMC V8's have always made good power and have good design built into them, but the increasing obsolescence in their parts and fuel consumption drive their cost of ownership up. Emissions regulations preclude their installation into most modern Jeeps. It should be noted here that the AMC engines are in no way related to the Mopar V8's, even if the CID designation (i.e. 360 vs. 360) may be the same.
Mopar "Hemi", 2002- (5.7L, 6.1L)
Few engines arrive on the scene with as much hype as the redesigned Mopar Hemi V8 did. Big marketing, big talk and pretty decent power figures came forth. Of course, it carried the "Hemi" name, which was more for copyright purposes than a mechanically accurate description of the head design. Whatever the case, it is a good motor and an improvement over the Magnum V8 engines, which the Hemi replaces. Fuel economy on the earlier Hemi versions won't dazzle too much. Later versions with Active Displacement improve on this, primarily at cruising speeds.
Hemi's are installed into Jeeps by a couple of specialty shops that have the cryptic Chrysler computer codes to do it. The engines and installations remain overpriced, and with time, things will shake out as they always do to see if they'll become more affordable and feasable, and if the shadetree installer will pick up on them.
Ford "Pinto", 1970-2001 (1.8L - 2.5L)
The Ford 1800, 2000, 2300 & 2.5L "Pinto" motor has long been a favorite swap into pre-1972 CJ Jeeps with the T90 transmission. They make unusual power for a four-cylinder, and fit very well into the engine bay of a short-hooded Jeep. The motor is avaialble in carburated and injected versions, and is found in Ford cars and small trucks from the early 1970's up through 2001.
GM Atlas I6 & I5, 2002- (4.2L, 3.5L)
The GM Atlas series of engines presented the world with GM's very refreshed view of the straight-six engine. Released in 2002 as the 4.2L Vortec, it took engineers and the automotive press by storm. It may be one of the most efficient truck I6 engines ever made, and it competes handily against other companies V8 offerings. It does, however, remain somewhat in the shadow of the GM LS & Vortec V8 engines.
As the Atlas engineering and tooling is modular from their inception, it has a five and four-cylinder siblings, the 3700 and 2800, respectively. These engines all share the same bellhousing bolt pattern with each other. However, individuals swapping these into Jeeps should understand that they do not share the same 90-degree Chevrolet V6, V8, I6, Iron Duke bolt pattern. The Atlas family can marry to a 4L60E auto with the appropriate bellhousing, as well as the GM AR5 transmission for the I4 & I5 versions. Engine mount availability is not yet there. Computer and wiring support is very good, as with the other GM engines.
Chevrolet I6, 1962-1990 (194-292)
The Chevrolet I6 engine made from 1962-1990, in displacements of 194 - 292 CID, is an installation possibility into many "long hood" Jeeps, including the CJ series, J Series, FSJ, M715/725 and YJ. They are good, solid motors. Individuals researching their installation should know that they have the same block / bellhousing pattern as the Small Block V8 series and therefore share the same transmission compatibilities as listed elsewhere on the Novak website. These engines were also GM equipped with angled engine mounting brackets that emulate the factory Small / Big Block V8 mounting bosses, and thus, will use the same Novak V8 mounts.
As these are longer motors, they do not install well into early CJ Jeeps. Also, the installer should consider that these engines do not generally enjoy the fuel economy or powerband as similarly displaced Chev V8 motors like the 283 through 327 Small Blocks.
Buick V8, 1968-1980 (350)
Buick's final and best V8 engine was the 350. It was introduced in 1966 and remained in production through 1980. This was the engine of choice in the J Truck and Wagoneer from 1968 thru 1971. This engine uses the same engine mounts as the Buick V6, and the same block / bellhousing pattern. It is compatible with popular GM manual transmissions and the GM TH400 and TH350 HydraMatics, granted they have the Buick "valley" block pattern; the Buick V8 does not share the same bolt pattern as the Chevrolet V8's.
Other GM V8's (Olds, Pontiac, Cad)
GM's Cadillac, Pontiac, Oldsmobile and Buick divisions have made some of the worlds greatest V8 engines, and many have been installed into Jeeps. They can be made to fit in many Jeep models - the Buick V8 being chief among them. The Chevrolet V8 is vastly more popular. While these all can often use the same bellhousing-to-transmission adapters or GM standard transmission as the Chevy V8, they do not enjoy the wide parts interchangeability of the Chevy V8. Some have oil filters or starters in inconvenient locations. Other factors usually related to physical shape or size make these a greater problem for installation than the Chevy V8, but for the Jeep owner who understands and prefers these good engines, they can make a good swap.
Other Four-Cylinder Engines (general)
There are a handful of great four-cylinder engines. The GM Iron Duke 150, Toyota 22R, AMC I4 and others come to mind. However, as a community of installers and aftermarket swap companies have to put their eggs into the baskets they do. We get occasional requests for these various installations and we recommend the installer going with good, standard solutions as much as possible. Additionally, as Jeeps continue to get larger and heavier, these motors do become less relevant.
As discussed elsewhere in the Novak Knowledge Base, most four-cylinders will disappoint in terms of power as well as economy.
Diesel Engines (general)
Diesel engines are a great idea for Jeep swaps. However, they haven't often materialized successfully past the idea stage. The lack of applicable, light-duty domestic diesel engines makes these swaps a discouragingly difficult process. Foreign diesels are usually quite advanced, but are difficult to find and maintain. We have researched this topic enough to be hopeful that these swaps will one day be more feasable than they currently are.
If you are considering a diesel engine for the sake of novelty, you may find that it requires more commitment and cash than novelty is worth. If you are seeking them for fuel economy or efficiency, you may consider a modern, clean burning fuel-injected gas engine set up against a properly geared drivetrain. We are totally aware that diesel fuel is inherently more powerful than gasoline by about 15%. However, converting all that power to mechanical energy is not easy. Conventional diesel engines do generate more heat than a similar gas engine, and their increased weight affects the Jeep's performance.
Also, the rush towards diesel engines in these domestic F-ohmyhell, C-blowyouaway and D-thumpin full-size-trucks, has driven the cost of diesel 8% past that of gasoline. Individuals wishing to install a diesel motor in a Jeep should add up the increased expense (time + cash) of the installation, in addition to the actual potential savings during usage.
This is our long way of saying "we're not there yet."
General Principles to Consider
There are two popular misconceptions about engine size that should be brought to light. The first mistake many make is in thinking that a small displacement engine will invariably give better gas mileage. This is only true if the small engine is in a lightweight, properly geared, and semi-aerodynamic vehicle. A small engine in a heavy vehicle with "tall" gears will perform poorly and give bad gas mileage. Any engine, when worked to the point where vacuum drops low enough to operate the power jets in the carburetor, or to lug, will give poor gas mileage. If too small an engine is used for the work to be done, it will operate at low vacuum for longer periods and use more gas than a larger engine that would not be working as hard. The added benefit of the larger engine is its reserve power.
The second most common error swappers make is to convert to an engine that is too large, from both size and displacement, for the vehicle. While a Small Block V8 is a great engine, there are sometimes better choices for smaller Jeeps, such as Buick and Chevrolet V6's, Ford 2000cc and 2300cc's, GM "Iron Duke" Fours and the like. Big Block V8's and heavy old I6's should hardly be considered in short wheelbase Jeeps! When planning a conversion into a CJ2A up through the CJ5's, remember that you are dealing with a 2500lb. vehicle. This, by all standards, is light, and that is one reason why these vehicles prove to be the most agile in the world. Adding an overburdening block of iron to smaller Jeeps will give disappointing results in terms of handling, braking and of course, breaking – of several components directly and indirectly between the block and the vehicle. Besides, fit into the engine bay is usually so poor that the work soon looks as poorly as it was thought out in such situations.
The trick is to match engine size to the load, then only use the reserve power when needed. Engine torque output is essentially related to cubic inch displacement of any engine. The RPM that maximum torque is produced at is related to the length of the stroke of any engine. A 230 CID "under-square" engine will make about the same torque as a 230 CID "over-square" engine but will do so at lower RPM due to its longer stroke. (An under-square engine has a bore that's smaller than its stroke.) Many swappers and engine enthusiasts prefer the challenge of running an optimum V6 to the power levels of V8's, and then reaping the weight and fit benefits both on and off-road.
Computers, Wiring and Fuel Injection
Some speak nostalgically about the days when engine electrical and fuel systems were about the simplest parts of an engine swap. Engine and vehicle management computers are now a major part of modern automotive systems, and therefore, a significant consideration when doing a conversion. Some don't gravitate towards fuel-injection, but most individuals embrace them now. Fuel injected engines are, by a long shot, the most common for Jeep conversions now. As the engine computer and the engine wiring harness are largely tied together, and should essentially be regarded as a unit. Connecting in the vehicle harness and relays is not that hard, especially if the installer will take some time with the engine wiring diagram and pinouts, and the Jeep wiring diagram. It becomes quickly apparent which wires to join.