by Bruce D. Osborn
- 1.1 Parts Needed and Suppliers
- 1.2 Engine Sources
- 1.3 Engine Removal
- 1.4 Transmission and Transfer Case Removal
- 1.5 Transmission
- 1.6 Transfer Case
- 1.7 Clutch and Bellhousing Information
- Drivetrain Assembly
- 2.1 Clutch and Bellhousing Installation
- 2.2 Assembling the Engine and Transmission
- 2.3 Assembling the Transmission and Transfer Case
- Installing the New Drivetrain
- 3.1 Engine Location
- Finishing Touches
- 4.1 Clutch Linkage
- 4.2 Saginaw Steering
- 4.3 Driveshafts
- 4.4 Brake Pedal
- 4.5 Exhaust
- 4.6 Radiator
- 4.7 Gas Pedal
- 4.8 Wiring
- 4.9 Brakes
- Parts Suppliers
The easiest thing to do would be to find a salvage yard CJ-5 with a V6, buy the entire drivetrain and replace the CJ-3B drivetrain with that of the CJ-5's. Unfortunately, Jeep used a weak T-14 transmission behind the V6. The CJ-3B had a stronger T-90 transmission. Simply swapping the drivetrains would result in a considerable sacrifice in transmission reliability. The best option would be to use the CJ-5 V6 engine with the CJ-3B transmission. But, the transmission bolt patterns are different so it's not possible to bolt the T-90 transmission to the V6 engine.
Advance Adapters Inc. provides the solution to this problem. They manufacture an adapter that allows the T-90 to be bolted to the V6 engine. This offers the best power and reliability possible using the best of two Jeeps. Additionally, it allows the exclusive use of Jeep parts. Buying replacement parts for a Jeep that has a Ford or Chevy motor and a Jeep transmission can be frustrating to say the least.
Note: This manual is not intended to be a stand-alone reference for the V6 engine swap. It is intended to be a supplement covering various problems that are not addressed in the references on the subject. You also need the Universal Jeep Service Manual, the Chilton Jeep 1945 to1987 Repair Guide, and the Advanced Adapters Jeep Engine and Transmission Conversion Guide.
Since your Jeep will now be a mixture of various parts from several different models of Jeeps, you'll need the Chilton guide to cover the new motor and clutch. The factory Service Manual is the best reference regarding the transmission and transfer case but early editions only cover Jeeps with four cylinder motors (hence the need for the Chilton manual to install the clutch). The Advance Adapters Manual covers the various adapter parts that you will need to install. See the Bibliography for sources.
There are pages in those manuals that will be referred to in this manual. It is necessary to have them at hand while reading this manual, and they also include numerous pictures and diagrams.
Here is a rough idea of the work that is required:
More detail on each of these topics is covered below.
1.1 Parts Needed and Suppliers
Mile Hi Jeep Rebuilders:
Republic or Jeeps Unlimited:
1.2 Engine Sources
Jeep used the "Dauntless" 225 V6 in two different vehicles from 1966 to 1970 -- the CJ-5 and the Jeepster Commando. Either engine will work fine. You can find them in the parts-for-sale section of the newspaper, on the parts-for-sale bulletin board at Mile Hi Jeep Rebuilders or at a salvage yard. Try to find the 225 odd fire and not the newer 231 even fire. The 231 does not have as strong a crank or nearly as much power. However, the bellhousing bolt pattern and the engine mount locations are the same. If a 225 cannot be located, a 231 can be used in its place. The 231 was used in Buick Regals from 1976 to 1984.
(Ed. note: Photo taken from the 1966 Jeep CJ-5 brochure. Thanks to Mike Boyink.)
It's preferable to obtain the flywheel with the engine since the engine is balanced with the flywheel at the factory. If this is not possible, you'll have to obtain one. If possible, try to buy the bellhousing with the engine also since they are hard to find (see 1.7 Clutch and Bellhousing Information).
1.3 Engine Removal
Drain the engine of radiator fluid. Remove the fenders, grill and radiator. LABEL all the wires connected to the engine and then disconnect them. If you forget to label the wires, you'll have to trace all of them back to the ignition switch and use a voltmeter to figure out which one is which when you wire the new motor. Willys never used standardized insulation colors on their ignition harnesses so a wiring diagram won't help you to do this. Label the wires carefully. Disconnect the fuel line, exhaust and the battery. Disconnect the clutch linkages. Support the engine and transmission and remove the bolts that secure the bellhousing to the transmission. Remove the engine. This is covered more completely in the Universal Jeep Service Manual (page 60).
The stock motor mounts must be cut from the frame. A hand held grinder with a cutting wheel works well for this. Be very careful not to cut off the front brake line brackets that are integral with the bottom of the motor mount. You'll need to carefully cut the mount in half, grind the rivets off the top and knock the top half of the mount off with a hammer. If the grinder bites and slips when you're cutting the mount you'll undoubtedly cut the brake line. Be very careful with the grinder.
1.4 Transmission and Transfer Case Removal
Remove the transmission and transfer case following the instructions listed in the Universal Jeep Service Manual (page 163).
The T-90 will need to have a new input shaft (Advance Adapters kit 716014) installed. Since the transmission must be completely disassembled to install the new input shaft, now is the time to rebuild it. In order to disassemble the transmission, the transfer case must be removed. Follow the directions in the Universal Jeep Service Manual (page 178) when removing the transfer case. The T-90 is not particularly strong and must be in good condition to accept the higher power input of the V6 engine. Rebuild parts are available from Mile Hi Jeep Rebuilders or JC Whitney. The Universal Jeep Service Manual has a very good section on rebuilding transmissions (page 163) -- the only thing that you'll be doing differently is installing the new input shaft instead of the stock one. The replacement of all bearings, seals and the synchronizer ring is the minimum amount of rebuiding you can expect.. Evaluate the gears and replace those that are worn. Pay particular attention to second gear, since it is prone to wear, causing the transmission to fall out of second gear when coasting.
The front input shaft bearing must be replaced. The new input shaft does not come with the bearing installed. Take the new input shaft and a new bearing (don't try and re-use the old one) to a machine shop and have them press it on. It doesn't cost much and it is very easy to damage the bearing if you try to hammer it on yourself. If the bearing is damaged, it will fail in short order. A new front bearing retainer is included with the Advance Adapters kit. Follow the instructions included with the kit when assembling the transmission in order to ensure that the input shaft oil seal is installed correctly.
1.6 Transfer Case
You should inspect the transfer case for wear. The intermediate shaft and its bearings will probably need to be replaced. If it's been awhile since the transfer case was rebuilt, the output shaft endplay should be checked. Endplay is adjusted by changing the number of shims between the case and the output bearing retainer. If the endplay is not adjusted correctly, the transfer case will be extremely noisy and the output bearings will fail prematurely. Again, there is a section in the Universal Jeep Service Manual on transfer case rebuilding (page 179). The transfer case is extremely strong and if rebuilt correctly, will accept the increased power input reliably. Mile Hi Jeep Rebuilders will have all the rebuild parts that you need.
1.7 Clutch and Bellhousing Information
The stock clutch will not work on the V6. You will have to use a GM 10-1/2" clutch. These parts can be purchased at most auto part stores. There are three different types of 10-1/2" clutches that will fit. Any one of them is fine if you can't find the part numbers listed above. Just make sure to buy the pressure plate, disc and throwout bearing at one store so that you get parts that are compatible with each other. Resist the urge to buy rebuilt clutch parts. The demands on a four wheel drive clutch are much greater than most other applications and rebuilt clutch parts aren't of high enough quality to use.
A Jeep 225 bellhousing must be obtained from a 1966 through 1970 V6 equipped Jeep. They are, unfortunately getting quite hard to find. Republic Jeep is a good source for the bellhousing. This will probably be the hardest part to find. You will also need a new flywheel. Jeep used two different ones; a 32 pound and a 53 pound version. The heavier one will yield the best off-road results. These are also available at Republic Jeep.
When the engine and bellhousing are assembled at the factory, they align the transmission bore with the pilot hole in the crankshaft (I didn't know this when I bought my engine). When you replace the bellhousing, you don't know where the pilot tip of the transmission input shaft is going to line up. It may only be off by fractions of an inch but when you consider how long the transmission input shaft is on a V6 conversion, it can end up really out of whack. Bellhousing misalignment is indicated by excessive pilot shaft bushing wear, which I discovered when I replaced the throwout bearing after a really fun romp in sand dunes outside of Pritchert Canyon in Moab. When I used a clutch aligning tool during the reassembly, suddenly a T-18 aligning tool would fit in the old pilot shaft bearing but wouldn't fit in the new bearing. There are really nice offset pins available for Chevy smallblocks that you can use to align the bellhousing, but nothing for the V6. My solution is a TH350 which is my next modification.
You'll need to assemble the V6 engine, transmission and transfer case before installing them in the Jeep. This is necessary in order to correctly locate the assembly in the chassis.
2.1 Clutch and Bellhousing Installation
Use the Chilton manual as a reference to assembling the clutch (page 333).
Use thread lock compound on all clutch component bolts. Make sure that you follow the instructions for the 225 and not the stock 134 engine. After you have installed the flywheel, assembled the clutch and installed the bellhousing, make sure that the throwout arm is positioned towards the motor side of the hole in the bellhousing and not the transmission side. The lever moves from front to back when you step on the clutch and it won't have enough travel to disengage the clutch if it's too close to the transmission side. If it turns out that it is in the wrong location, you'll need to install an adjustable throwout lever pivot from Mile Hi Jeep Rebuilders. It's impossible to tell if you'll need an adjustable pivot until you assemble the clutch. Make sure to install a rubber boot (Mile Hi Jeep Rebuilders item) over the throwout lever opening or sand and dirt will get into your clutch.
2.2 Assembling the Engine and Transmission
The transmission needs to have the Advance Adapters transmission-to-bellhousing adapter (712502) bolted onto the front of it. It's made out of aluminum so it's very easy to strip the bolt holes in it. Be sure to torque the bolts to the specifications supplied with the adapter. It's also a good idea to use a thread lock compound on these bolts since they tend to vibrate loose. Insert the transmission input shaft into the bellhousing and slide the transmission in flush with the bellhousing. Bolt the adapter to the bellhousing. Again, use the torque specifications supplied and thread lock compound.
2.3 Assembling the Transmission and Transfer Case
See the section in the Universal Jeep Service Manual (page 181).
3.1 Engine Location
Engine location is critical. There are two major issues to keep in mind:
1) The engine should be as far forward in the Jeep as possible. This results in two benefits; the engine fan is closer to the radiator, cooling the engine better and the rear drive shaft is as long as possible. A longer rear drive shaft turns at angles that are more favorable to the drive shaft Universal joints. This in turn leads to longer Universal joint life. It's not uncommon for short drive shaft Universal joints to fail in six months or less.
2) The engine should be as far to the driver's side of the Jeep as possible. This gives the maximum amount of clearance between the front drive shaft and the bellhousing. When the front axle comes up (picture driving over a rock for example) the front drive shaft comes up also and can rub against the bellhousing. A small amount of rubbing seems to be unavoidable since every V6 conversion examined (including the author's) has it. Excessive rubbing will shear the front drive shaft and they are expensive to replace.
This is how to correctly place the engine:
Remove the stock steering setup. Allthough the Advance Adapters Manual states that it is possible to retain the stock steering, it is incorrect. It is not possible to place the engine properly with it in place (it is possible to do so in a CJ-5 but, they have a little bit more room under the hood than the CJ-3B). Hang the engine, transmission, transfer case and transmission cross member as a unit from an engine hoist. Move the whole assembly into the approximate location where it will be located in the Jeep chassis. Level the drivetrain untill the crossmember is touching the frame. Slide everything towards the front of the Jeep until the crossmember bumps up against the rear of the front axle spring mounts. This is as far forward as the engine will go. Now bolt the motor mounts on to the engine. Move the whole assembly as far to the drivers side as is possible while making sure that the motor mounts are still over the top of the frame. Check the clearance between the drive shaft and the bellhousing. The idea is to maximize clearance but still place the motor mounts in a position that will be strong when they're welded into place.
On offset of about 1" is possible without modifying the crossmember and this should give you enough room for the driveshaft to move freely. When you are absolutely sure that you have the drivetrain in the best spot, weld the motor mounts to the top of the frame. If you are not a good welder, contact a portable welding company and have a qualified welder do the work. It's important to have strong, deep welds on the motor mounts. Drill holes in the frame and bolt the crossmember into it's new location. Be careful -- do not get underneath the drivetrain until you have bolted and welded it into place. It weighs in excess of 500 pounds and it will kill you if it falls on you.
4.1 Clutch Linkage
It is possible to fabricate a clutch linkage using the stock linkage. However, the linkage is very difficult to adjust and goes out of adjustment every time the frame flexes from off-roading. A better solution is to install the Advance Adapters chain clutch controller (part number 716640). It is expensive, but is easy to adjust and maintains adjustment much better than the stock setup.
4.2 Saginaw Steering
Since the stock steering was removed in order to properly place the drivetrain, you'll need to replace it with a Saginaw steering setup. The Advance Adapters Conversion Manual will show you the proper way to install it, as well as provide the source for parts. A salvage yard 1974 CJ-5 is an excellent donor for steering parts. A salvage yard Jeepster Commando is the best source for parts since it is possible to do the conversion without any Advance Adapter parts. Unfortunately, these parts are next to impossible to find since Saginaw steering is a popular modification for all Universal Jeep owners.
The rear driveshaft will need to be lengthened and the front driveshaft will need to be shortened. This has to be done by a qualified driveshaft repair shop. The driveshafts need to be carefully balanced or they will shake themselves to pieces. If this happens, the driveshaft can drop down and wedge between the Jeep and the road, possibly resulting in a roll-over. In order to measure the length of the new driveshafts, measure the distance between the output yoke of the transfer case and the input yoke of the differential. Do this for the front and the rear driveshafts. Write it down and give it to the driveshaft shop when you take them the driveshafts. While the driveshafts are being rebuilt, it's best to have new Universal joints installed. Then the shop can balance the driveshafts with the new Universal joints installed, which gives a better balance and less wear from vibration.
4.4 Brake Pedal
Now that the engine has been offset to the driver's side, the brake pedal will hit the bellhousing when depressed. This prevents full application of the brakes. The pedal can heated with a torch and bent to give clearance. If you have someone step on the pedal while you watch where the pedal hits the bellhousing, you can measure how much and where the pedal needs to be bent. Take it to a welding shop for modification.
It is possible to use the stock V6 exhaust manifolds but it is a difficult and expensive proposition. The exhaust pipes will have to be custom made and the driver's side exhaust manifold will interfere with the placement of the Saginaw steering setup. A cheaper and easier alternative is to use Hedmann Headers for a CJ-5. They will clear the steering gear and drop out behind the front wheels. From there, inexpensive mufflers can be bolted on. Use the smallest ones that Checker Auto parts stocks. Remember that you will have a dual exhaust and will need two of everything. The rear of the muffler needs to be supported or the muffler will crack at the inlet and break off.
It is necessary to trim the fender skirts in order to fit the headers. Also, since the mufflers are outside the frame rails, directly behind the front wheels, they are susceptible to damage from rocks. This setup is also quite loud. But, it does make for good engine power since there is a minimal amount of backpressure. The only other alternative is the most expensive one: the fabrication of a completely custom exhaust system from the cylinder heads back.
The stock radiator is an old fashioned low pressure type. Do not put a newer high pressure cap on it because the increased pressure will cause it to burst. It is possible to use it but it will need to be modified. It is marginally capable of cooling the V6. The lower hose connection on the radiator will need to be moved from the driver's side to the passenger side. Any radiator shop can do this for you. Have them install a 90 degree elbow that spills directly to the passenger side Now is a good time to have the radiator disassembled and cleaned. It costs a little more but it will ensure that the already marginal radiator is performing as well as possible.
The elbow will allow enough room to use a 13 inch engine driven fan. An electric fan will not cool the engine adequately. The combination of an engine fan and an electric fan on the front of the radiator works the best. Your Jeep will have overheating problems in very hot weather after sustained hill climbs. The alternative is to have a radiator shop custom build a four row radiator. If you live in a hot climate, this might be a necessity.
4.7 Gas Pedal
You will not be able to use the stock gas pedal. The linkages from the pedal to the carburetor use the stock engine to support them. Since that engine is gone, it's easier to replace the entire setup than to try and modify it. The gas pedal from a 1975 CJ-5 with a straight six engine will bolt to the firewall from the inside of the body tub. This pedal has a cable linkage that is compatible with the linkages of the V6 carburetor and is about the right length. The only difficult installation item is the drilling of a square hole. The gas pedal end of the cable cover plugs into a square hole in the fire wall. The square hole anchors the cable cover, keeping it from moving with the cable as you step on the pedal. To make the square hole, drill a round hole in firewall and use a small file to square it up. The carburetor end of the cable is a direct bolt in installation.
You can find the pedal by canvassing your local junkyard. This part is fairly easy to find. The cable can be ordered new from most auto part dealers.
The easiest way to wire the engine is to cut the wiring harness at the firewall and install a junction block. You'll need at least a seven terminal block, depending on how you wire the engine. Then wire the engine back to the junction block.
The V6 came with two different kinds of alternators, which do not match the wiring harness of the CJ-3B; the stock motor uses a generator instead of an alternator. JC Whitney carries a GM style one wire alternator wiring kit that makes alternator wiring much easier. It comes with an installation manual so there will be no instructions listed here. You should not have to make any modifications to the wiring harness that supplies the headlights. Make sure you don't cut it instead of the engine wiring harness.
(Ed. note: See also Eric Lawson's description of installing an alternator using the CJ-3B wiring harness.)
An important consideration when installing the alternator is the distance between the alternator and the battery. The Universal Jeep frame is very flexible, which allows the axles to maintain contact with the ground; this way engine power reaches the ground instead of uselessly spinning a wheel that is hanging in the air. Unfortunately, all this flex allows the engine to tip toward the battery, bringing the alternator fan into contact with the battery. After the fan cuts a hole in the battery, acid is sprayed throughout the engine compartment which strips the paint down to bare metal. Also, it's hard to get home with a hole in the battery.
There are two solutions: 1) The battery can be clad in a 1/8" steel plate shod which prevents the alternator fan from chewing a hole in the battery. This modification doesn't seem to affect the alternator reliability. 2) The battery can be relocated to the passenger side firewall. This will interfere with the stock heater hoses, indicating major heater modifications, but is probably the best solution.
(Ed. note: Photo shows a Buick 231 with battery on the firewall,
in Jon Paulsen's CJ-3B.)
Now that your Jeep has twice as much horsepower, you should consider installing bigger brakes. The 11" drum brakes off any 1976 or later CJ will replace the stock 9" brakes. The brake conversion is a direct bolt on swap with the exception of the brake lines. You may need to use a pipe fitting adapter in order to bolt the flexible brake line to the solid brake line.
Since the front brakes do most of the stopping, it is adequate to upgrade them only. If 31" or larger tires are installed, it is desirable to upgrade the rear brakes also. You will need to have the stock hubs pressed out of the original brake drums in order to install larger brakes from a CJ-7. The 10" brakes off a V6 equipped CJ-5 are direct bolt in replacement.
(Ed. note: See also Jon Paulsen's Tech Tip on converting to 11" brakes.)
If this manual has made an engine conversion sound easy, don't be misled. It is hard work and not for the faint-hearted. Plan on spending weeks preparing for and weeks actually doing the work. Then plan on spending weeks ironing out all the problems that you'll find as you drive the Jeep. Every conversion takes on a character of its own and it's impossible to predict what problems will crop up in the process. However, if you follow this guide, you'll avoid the most frustrating (and expensive) problems that challenge most people.
Probably the most valuable information resource when it comes to a Jeep engine conversion is the staff at Mile Hi Jeep Rebuilders. If you're stumped by a problem, go down and ask the staff about it. They don't mind spending time with their customers explaining what needs to be done and what parts you'll need (it also helps if you buy those parts from them). They have an amazing inventory of Jeep parts as well as an profound understanding of Jeeps.
Finally, it has to be considered whether it's worth the effort to install a V6 in a CJ-3B. The answer is absolutely yes. The V6 transforms a temperamental, anemic Jeep into a consumate off-road vehicle. There simply is no contemporary alternative that performs as well off-road, irrespective of sticker price.
-- Bruce D. Osborn
Advance Adapters, 800-350-2223, P.O. Box 247, 1645 Commerce Way, Paso Robles, CA 93447
JC Whitney, 312-431-6129, 2319 S Throop Street, P.O. Box 8410, Chicago, Il 60680
Jeeps Unlimited, 303-666-9020, 4245 Weld County Road 6, Erie, CO 80516
Mile Hi Jeep Rebuilders, 303-629-0378, 724 Federal Boulevard, Denver, Colorado 80204
Republic Jeep, 303-279-9209, 17169 So. Golden Road, Golden, CO 80401
CHILTON Repair and Tune-Up Guide: Jeep 1945 to 1987 (1987), Radnor, PA: Chilton Book Company (ISBN 0-8019-7675-8)
Instruction Manual: Jeep Vehicles 1941-1990 Engine and Transmission Conversion Kits (1994), Paso Robles, CA: Advance Adapters, Booklet No. JP001
Service Manual, Jeep Universal Series (1965), Newport Beach, CA: Original Reproductions, Form SM-1002-R6
Return to Tech Tips on The CJ3B Page.
Also on The CJ3B Page, see Parts Illustrations, Technical Information Sources, and Links to parts sources on the web.
Note: Peter Bauer wrote to say, "I did the Buick conversion with my CJ/MB mixture last year. One suggestion: I had to use the Buick 231 V6 instead of the 225 because here in Europe these engines are hard to find. You are right, that these engines, due to their low compression, are not very powerful. But I changed this with a set of TRW pistons with 10.5:1 comp. ratio. (PAW $350, forged aluminum.) We tested this against a 225 Dauntless and there's no difference in the output. (The 225 has 9.5:1 comp. ratio.) I used a BOP adapter plate like is used for adapting Chevy auto.trans. to BOP engines. The bellhousing and the transmission (B&W T5, five speed) is from an Iron Duke-equipped CJ (hydraulic clutch linkage, Chevy bolt pattern!) The biggest advantage of the Buick 231 is the availability of spare and performance parts."
Jeff Burch mentions that Buick V6's are available from Remanufactured.Com.
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