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Jeep V8 Engine Swap Options

Posted in How To: Transmission Drivetrain on June 1, 2011 Comment (0)
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Photographers: General Motors

I had just completed an AX15 swap behind the 2.5L in my ’89 Wrangler. And wouldn’t you know it, shortly afterwards the engine started getting tired and developed sporadic drivability issues that made me question its reliability on any drive more than 20 miles from home. So, rather than rebuilding my stock 117hp, 135lb-ft TBI four-banger, I began searching for a replacement engine to swap in its place. In my opinion, a V-6 or I-6 conversion is just too much work for the power and drivability gains they offer, so I immediately started searching for a complete, running V-8 donor vehicle from which I could yank everything I’d need: engine, fuel system, accessories, exhaust, and sensors. I also searched for complete take-out engines, but was surprised at some of the prices being asked. Still, I soldiered on.

At first, I thought I wanted a dirt-simple TBI Chevy 350. I gave myself a max budget under $1,000 to score my new powerplant (not including adapters or swap components), but you know how things go. First, all of the donor vehicles I found in my price range were either beat to death or had over 200,000 miles on themand all of the take-out engines looked suspect. I would’ve had to crack open any of these engines and perform a valve job, maybe re-ring them, or even do a complete rebuild to get the kind of long-range reliability I was after. That adds time, money, and effort. The TBI search evolved into a TPI search, which evolved into a Vortec search, then on to Chrysler and then Ford V-8s.

Eventually I scrapped my whole search for older engines and moved on to more-modern options, which you’ll read about next month in Part II of this story. In Part III, I’ll introduce you to my choice of engine that’ll actually get swapped in front of my little Wrangler’s AX15 and start the install. Finally, Part IV will wrap up the install and give you a full drivability review, including mileage and acceleration numbers. Until then, here are some good junkyard engine swaptions for any Jeep model.

Chevy TBI 305/350
Years Manufactured: 1987-1996
Found In: GM put the LO5 350 TBI (throttle body injection) engine in just about everything. You’ll find the 210hp/300lb-ft engine in pickups, vans, Blazers, Suburbans, and cars like the Camaro or Caprice sedan and wagon. Most-commonly, you’ll stumble across the pickup models. The 170hp/255lb-ft L03 305 could be found in these chassis as well from ’88-’92, so be sure to check the rear of the block next to the distributor. The 350s will have a 5.7L and the 305s will have a 5.0L cast atop the bellhousing location. In ’93-’95 the 305 got a bump in torque, up to 275lb-ft, but horsepower remained the same at 170.

Pros: The injection system, sensors, and harness are very simple and easy to understand, which can make swapping easy. If you’re starting with a TBI-injected four-cylinder Jeep you’ll be able to use your stock in-tank fuel pump. Also, the low-pressure TBI system doesn’t require expensive high-pressure fittings and lines. And although it doesn’t look like a powerhouse on paper, the 5.7L LO5’s power and torque curves are very linear and come in right off-idle, resulting in an exceptional drivability and slow-speed off-road performance. Even the 305 makes for a nice upgrade that’s not a total gas hog.

Mounting: Advance Adapters and Novak Conversions make a plethora of bolt-in and weld-in motor mounts and/or engine crossmembers to physically get the engine in many Jeep chassis. Removal of the factory motor mounts would be required in any instance.

Mating: With some exceptions (Peugeot for example), if your Jeep came from the factory with a six-cylinder your existing transmission is up to the task of handling a TBI 350 or 305. Just use your head. Advance and Novak offer conversion bellhousings and bellhousing adapters for manual transmissions and adapter plates for autos. If you’re dealing with a four-cylinder, plan on swapping transmissions. You’ll find transmissions ranging from SM465 four-speed manual, TH400, TH350, TH700R4, and the 4L60E behind the TBI V-8s. Any one of these can be mated to a Jeep transfer case and makes for a very good off-road transmission.

Cooling: The radiator inlet/outlets are opposite from a standard AMC or Chrysler-era CJ, Wrangler, XJ, and so on. You could have the inlets and outlets moved at a radiator shop, but the cooling capacity of some factory Jeep radiators would be questionable with a V-8, so it’s usually best to go with an aftermarket conversion radiator as offered through Advance Adapters, Novak, or any one of a dozen radiator companies you can find on the web. Most often there’s a bolt-in solution. The factory GM mechanical fan can often be retained with good results, or a single or dual electric fan is another option.

Fueling: You’ll need either an in-tank or external electric fuel pump regulated at about 9-14psi. Due to the relatively low pressure, you can use injection-rated rubber hose with hose clamps where applicable.

Wiring: If you don’t have the skills or patience to separate the factory GM harness from the donor chassis, there are numerous aftermarket TBI harnesses available that will operate the factory GM computer, including Painless Performance, Rod Francis Wiring, Hotwire Auto, Speed Scene Wiring, Howell, Turbo City, and more.

Cautions: The factory TBI computer is a speed-density system that runs off pre-determined air/fuel tables. If you’re looking to modify your power levels with stuff like aftermarket camshafts, intake manifolds, head swaps, or even major exhaust modifications you’ll probably have to have a new chip burned to prevent the engine from running too lean and having detonation issues. Also, don’t try to run a 305 computer on a 350 and vice-verse. They just won’t perform correctly. If you’re going GM TBI it’s usually best to keep the mods to a minimum, or not mod at all.

Chevy TPI 305/350
Years Manufactured: 1985-1992
Found In: The LB9 305 TPI (tuned port injection) was used in automatic-equipped Camaro and Firebird models from ’85-’92 and in manual-equipped models between ’87-’92. Of the LB9 models, the ’85-’87 years offered 190hp/275lb-ft. The ’88s bumped the power up to 195hp on the auto and 215hp on the manual-equipped vehicles. The power differences were thanks to a different camshaft to keep the auto happy. In 1989 power jumped to 230hp for both transmissions and in 1990 a mod-friendly mass air system replaced the older speed-density system. The output of the LB9 remained at 230hp until the end of the run in 1992. The L98 350 TBI began its run in the ’87 IROC-Z Camaro and Firebird with auto transmission and was rated at 225hp/330lb-ft. In 1988 the L98 got bumped up to 230hp/330lb-ft and then again to 240hp in 1989. The switch from speed density to mass air resulted in no additional power for the ’90 models, but in 1991 the power was bumped again to 245hp/340lb-ft through the end of the L98 in 1992. Corvettes also got the L98 beginning in 1985, but unlike the F-body versions the Corvettes got aluminum cylinder heads in about mid-1986. Power ratings were slightly higher than the F-body models (by about 5hp/10lb-ft) but that’s generally attributed to the Vette’s free-flowing exhaust and marketing hype and not internal engine differences.

Pros: The long runners of the TPI manifold resulted in exceptional port velocity and a table-flat torque curve off-idle up into the 4,000 rpm range. With an overdrive automatic, it’s not uncommon to hear of TPI 305s knocking down mid-20 mpg and even the larger TPI 350s can be fuel misers. The later ’89-up 305s are bargains since their 230hp/275lb-ft rating rivals the early TPI 350’s 225-230hp output, although admittedly it does give up a lot of torque. You’re much more likely to stumble onto a 305-powered F-body than you are a 350-powered car and you’ll pay less to boot.

Mounting: The TPI will mount the same as the TBI 350. The TPI engines feature a small-cap distributor, so firewall clearance often isn’t an issue like with earlier HEI-equipped engines.

Mating: The TPI engines can be mated to the factory six-cylinder manual or automatic transmission with an adapter. Again, ditch the four-cylinder transmissions or early, weaker six-cylinder trannies. The later TPI 350s put out a lot of torque, so use common sense with the throttle if you’re retaining a stock Jeep manual. Most Jeep six-cylinder autos will absorb the TPI 350’s power without issue. If you’re retaining the factory GM transmission, keep in mind the five-speed manual doesn’t make the best swap candidate in a Jeep. If you’re starting with a four-cylinder or Peugeot-equipped six, it may be better to try to score the F-body’s TH700R4 and adapt it to your factory T-case.

Cooling: See TBI 305/350

Fueling: The GM TPI requires between 43-45psi of fuel pressure. You can use an internal or external aftermarket pump, or a factory in-tank pump from a HO 4.0L application. Keep in mind, some Jeep pumps don’t regulate in the tank. If your Jeep has a fuel return to the tank, it’s an externally regulated model and will require an external pressure regulator if your donor engine doesn’t have one on the fuel rail. If there is no return line like in many XJ, YJ, and TJ, the in-tank Jeep pumps are internally regulated at about 46psi, which is fine for use with the TPI engine. Because of the higher pressures, you’ll need to use dedicated pressure-rated fittings and hose when building and adapting your fuel lines.

Wiring: If you don’t want to use or can’t find a factory GM computer Painless Performance offers its Perfect Engine Management system complete with MEFI4 computer and plug-in harness. Otherwise, run the GM computer and check the harness companies listed in the TBI 305/350 section.

Cautions: It is said GM designed its TPI system for the 305 engine with a goal of great off-idle torque, mid-range power, and good mileage numbers. They definitely delivered, but when used on the larger 350 engine the long intake runners are out of breath around 4,000rpm. If you want the 350 and plan on engine upgrades like a cam or head swap, plan on replacing the lower intake plenum for one with shorter LT1-style runners. Costs add up fast, so if you want more power than the 350 offers, it’s best to go straight to the Vortec or other later-model engines.

Chevy Vortec 350
Years Manufactured: 1996-1999
Found In: GM phased the L31 Vortec 350 into its ’96 light truck lineup, including Chevy and GMC pickups, Blazers, and Suburbans. The L31 put out a very solid 255hp/350lb-ft, making it more powerful than the best TPI ever offered. And they made millions of em.

Pros: General convention holds the ’96-’99 Vortec cylinder heads as one of the best factory iron heads ever produced for a V-8 engine. The L31 used a hydraulic roller camshaft, low-tension rings, an exceptionally durable bottom end, and has proven to be a very reliable and long-running package.

Mounting: See TBI 305/350.

Mating: See TPI 305/350 for the majority of info. If you’re looking to retain the factory GM transmission, the L31 could be backed by a 4L60E, 4L80E, or NV4500 transmission.

Cooling: See TBI 305/350

Fueling: The Vortec 350 uses a special poppet-style injector arrangement mounted inside a weird spidering plastic intake manifold. The relatively small injector size means fuel pressure is critical. It’s not a high-volume system and really requires at least 55 psi to run correctly. Ideally a L31 is happiest with 60-68 psi, which means running an aftermarket in-tank or external fuel pump or making a factory GM in-tank pump work. Novak Conversions actually makes a nice retrofit Vortec fuel pump that supplies 58psi, or if you run an external regulator you can modify your tank to accept a PN E2065 pump from NAPA, which will deliver a max of 90-95 psi. Just don’t forget to regulate it down!

Wiring: GM itself used to manufacture a wiring harness to convert older TBI-powered light trucks to the L31, but the harness hasn’t been produced for years. No worries, though, as many of the companies offering TBI and TPI harnesses also offer harnesses for the L31 Vortec.

Cautions: The L31 factory computer will support modifications, but if you plan on keeping the poppet-style injectors and manifold in place (and if you’re swapping you probably are) you’ll be limited to about 400hp, which isn’t anything to sneeze at. Cams with more than about .470-inch lift will require new valve springs with special attention paid to coil bind.

Dodge/Jeep 5.2L/5.9L Magnum
Years Manufactured: 1992-2002
Found In: For the ’92 model Ram and Dakota pickups and vans, Dodge introduced a reworked version of its old 318LA engine they dubbed Magnum that put out 220hp/280lb-ft. The new Magnum had multiport fuel injection, different cylinder heads, flywheel, oiling, and other minor differences from the standard Chrysler LA small-block. In 1993 the 5.2L was added to other Chrysler products like the Jeep Grand Cherokee. Power ratings vary widely from model-to-model, but the 5.2L Magnum put out around 220-225hp/285-295lb-ft with a best of 230hp/300lb-ft. Differences in output stemmed mostly from different exhaust packaging. In 1993 Chrysler introduced a larger 5.9L Magnum rated at 230hp/325hp, which grew to 245hp/335lb-ft in 1998. The final year of Magnum production was 2002, although some 5.9L Magnums snuck their way into ’03 Ram chassis early in the production run.

Pros: The Magnum engines are anvil-tough and many of the accessory fittings (A/C connectors, alternator, fuel lines) and wiring connectors are the same as similar-year Jeeps (TJs especially). If you’re looking to score a donor engine with its factory-issued transmission still attached, many were offered in 4x4 Dodge and Jeep applications that used the same six-bolt, 23-spline T-case as most modern Wrangler, XJ, ZJ, and even some CJ vehicles.

Mounting: Advance Adapters and Novak both make weld-in motor mounts to install the Magnum engine in many different Jeep chassis. The Magnum is a relatively tight package, especially when the factory exhaust manifolds are retained. Be warned, only the 4x4 Dodge trucks use the required rear-sump oil pan, necessary for axle clearance in a Jeep chassis. The 2WD applications use a center-sump pan that must be swapped. Also, the 5.2L and 5.9L engines (2WD or 4WD) use different oil pans. You can’t fit a 5.2L pan on a 5.9L and vice-versa

Mating: Here’s the sticking point: there really aren’t any adapters to mate the Chrysler V-8s to many Jeep transmissions: especially the desirable late-model years. Normally you’ll be stuck trying to score the Dodge transmission. Early Dakotas came with an AX15 behind the Magnum transmission, but most manual-transmission Dodge trucks used either an NV4500 or NV3500. The NV3500 is basically an NV3550 with an integral bellhousing. Otherwise, most of the vans and many Ram, Dakota, and Cherokee models will have the 42RE or 42RH four-speed auto.

Cooling: The cooling inlet/outlet locations are different on the Magnum V-8 than on a Jeep four- or six-cylinder, so it’s just better to go with an aftermarket radiator and upgrade your cooling system while you’re at it. You can make the Magnum’s mechanical fan fit inside a stock Wrangler’s 4.0L shroud fit, or you can go to aftermarket electric fans.

Fueling: The Magnum V-8 requires the same 45-46 psi as most HO 4.0L and MPI 2.5L Jeep engines. Furthermore, the fuel rails commonly use the same fitting. Often, it’s a case of simply plugging in the fuel line on a newer MPI 4.0L or 2.5L Jeep. If you’re dealing with an off-brand Jeep, chances are you can make a factory YJ or TJ tank and in-tank pump work with your application. Again, use high-pressure hose and fittings if building or modifying your fuel lines.

Wiring: The Magnum computer can be made to talk to all the later-model Jeeps’ gauges and sensors, which can technically make a smog-legal swap easier to realize. If you don’t have the patience to combine the harnesses yourself, Hotwire Auto specializes in Mopar conversions like this and can make it a plug-and-play, smog-legal affair.

Cautions: Be careful when shopping for aftermarket or used Chrysler V-8 parts, as many ’92-up Magnum parts don’t interchange with ’91-earlier LA engines. Some components that come to mind are rocker arms, pushrods, flywheels, intake manifolds, and even some front accessory brackets. Also, the 5.2L and 5.9L engines use different driver-side engine brackets, so make sure you specify which engine you have when ordering installation kits.

Ford HO 5.0L
Years Manufactured:1986-1992
Found In: In 1986 Ford introduced the compact HO 5.0L rocket in its Mustang GT and LX models. The 90-degree V-8 was rated at 225hp/300lb-ft and ran a speed-density MPI injection, rowdy hydraulic-roller camshaft, and remained unchanged through the ’88 model year. In 1989 a mod-friendly mass-airflow EFI was introduced, along with a slightly tamer camshaft. This change is said to have dropped power a bit, but in reality it allowed the engine to better cope with aftermarket and environmental changes. With the exception of the Cobra models, the HO 5.0L in the ’Stang remained unchanged until 1993, when hypereutectic pistons replaced the factory forged jobbies and dropped power to 205hp. In 1988 the HO 5.0L was installed in Lincoln MK VII vehicles and remained unchanged (speed-density EFI included) through the ’92 models. The HO 5.0L also popped up in some ’91-’93 Thunderbird and Cougar models. However, the big score is to find a ’97-’01 Explorer or Mountaineer with the 5.0L engine. These got Ford’s excellent GT-40 heads and Cobra intake, although the blocks and pistons aren’t as durable as the earlier true HO 5.0L engines. A lame-duck cam limited these SUV engines to 215hp, but installing a factory 5.0L Mustang cam bumps that to 300hp easily.

Pros: It’s a super-compact, lightweight powerhouse with incredible durability. With roller camshafts, forged pistons, and high-nickel blocks, the 5.0L could rev to the stratosphere and would last well past 200K miles. Even today it’s not uncommon to see high-mileage blocks exhibiting very, very little cylinder wear.

Mounting: For starters, if you’re working with a ’87-’95 2.5L YJ, Advance Adapters has a set of bolt-in motor mounts that utilize your factory frame brackets. No cutting is required. Otherwise, Advance Adapters and Novak both offer myriad weld-in engine mounts for specific and universal Jeep chassisMating: Both Advance Adapters and Novak offer a number of different methods of adapting the Ford engine to the factory Jeep transmission including conversion bellhousings, bellhousing-to-transmission adapter plates, and automatic adapter plates and flexplate spacers. We haven’t really been fans of the Ford auto transmissions off-road and the Mustang T5 isn’t easily adapted to the Jeep T-case, but you could use a Ford T-18 or NP435 or a NV4500 with a conversion bellhousing if you can’t or don’t want to retain a Jeep transmission.

Cooling: The Ford 5.0L shares the same cooling hose inlet/outlet location sides as the Jeep 2.5L and 4.0L engines. We’d recommend adding a heavy-duty replacement Jeep radiator if your old radiator is in poor shape, but you should be able to retain your factory Jeep radiator in most instances. Electric fans will make your life a lot easier.

Fueling: The HO 5.0L requires around 42-50 psi fuel pressure with an external regulator and fuel return line. The factory externally-regulated 4.0L Jeep pump will fuel the 5.0L just fine and even the factory in-tank, internally-regulated pump can be made to work in a pinch. However, many Ford vehicles used an externally-mounted fuel pump, so it’s often easier to just purchase the factory Ford pump and mate it to your fuel tank. Remember, high-pressure fuel lines require dedicated high-pressure fittings and hoses.

Wiring: The earlier speed density systems are admittedly easier to work with when swapping. As long as you plan on leaving the engine mostly-stock, the speed-density won’t need to make major changes to the air/fuel tables and all will be well. Otherwise, Painless Performance, Summit Racing, and a host of other companies offer wiring harnesses for the mass airflow systems. The speed-density and massi air systems use different computers, harnesses, and some sensors, and converting systems isn’t exactly cheap, so pick your poison before you buy your swap candidate. Also, you’ll need the correct ECU for a manual or auto. RJM Injection Technologies offers trouble-free harnesses, wiring, and ECU conversion components that’ll make the swap a lot easier.

Cautions: Most Mustang and other Ford applications use a front-sump oil pan that will require swapping out. Use a rear-sump oil pan and pickup, which you can purchase through Summit Racing.

Sources

Summit Racing
Akron, OH
800-230-3030
SummitRacing.com
Advance Adapters
Paso Robles, CA 93446
800-350-2223
www.advanceadapters.com
Hotwire Auto
Mena, AR
479-243-9115
www.hotwireauto.com
Howell Engine Developments
Marine City, MI 48039
810-765-5100
www.howellefi.com
Ron Francis Wiring
Chester, PA 19013
800-292-1940
http://www.ronfrancis.com
Turbo City
Orange, CA
714-639-4933
www.turbocity.com
Novak Conversions
Logan, UT 84321
435-753-2513
http://www.novak-adapt.com
RJM Injection Technologies
517-455-7352
http://www.rjminjectiontech.com
Speed Scene Wiring
210-834-1360
http://www.speedscenewiring.com

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