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1945-1967 Civilian Power Wagon V8 Conversion

1942-1945 WC 3/4 Ton Weapons Carrier V8 Conversion

Price: $370 plus shipping          

The WDX 318/360 V8 installation kit for use with the NP435/NP420 transmission contains the following:

2 ea. Front engine mounts.

2 ea. Rear engine mounts.

1 ea. Throttle assembly.

1 ea. Throttle cable

4 ea. Rubber vibration isolators.

1 ea. Upper radiator hose and clamps.

1 ea. Lower radiator hose and clamps.

1 ea. Hardware set for installation of these parts.


On your end you will need to buy the following:

1- 318 or 360 engine.

1-1961-1968 hydraulic clutch type bellhousing.

1- 318 or 360 V8 flywheel and pressure plate, (the flywheels are not interchangeable).

1- 1961-1968 318 clutch pressure plate if you are using an early NP435 (65-68).


General information:

Which gearbox should you use?

1. If you have a 1956 or earlier PW and do not have or want a PTO wench get an NP435 tranny from a '65 to '68 truck and install it. It will bolt up to the hydraulic bellhousing without any mods and has full syncros. You will need to get a conversion yoke and U-joint part# 357X ($120) from Spicer to fit the 35 spline NP435 output shaft and the PW intermediate shaft. You can also use the '61-'68 NP420 box and use the original PW output yoke on it.

2. If you have a 1957 or later PW and do not have a PTO wench, find a '61-'68 NP420 tranny and remove the input shaft and install it in your WM300 tranny. Now it will bolt up to the '61-'68 hydraulic bellhousing.

3. If you want a PTO wench you will have to find a short output NP435 tranny with dual PTO windows and purchase a PTO from Chelsea for approx. $550. Quite often used PTOs can be had at swap meets for $20-$50. See tech topics for complete info on NP435 conversion.

These parts will allow you to bolt your new engine into a Power Wagon using the original engine mount points. Your best bet for an economical installation is to find a good low mileage truck that has been totaled and buy the engine, flywheel and bellhousing along with any accessories including the power steering pump, hoses and brackets. If the donor truck is a 1972-1978 Dodge 4X4 with a reverse rotation saganaw steering gearbox, (when you turn the input CW the output should turn CCW) get that too and you will be ready to install your power steering as well. Try to find an engine that has 4 bolt front mount flanges as they are stronger than the 3 bolt ones used on some of the engines.

We have an adapter plate that bolts to the side of the NP435 and allows you to attach your original transfer case and E-brake levers with it.


Read the chapter in your trucks technical manual on power plant removal, the following is only a basic outline of the procedure.

1. Remove your hood, fenders, fender liners and radiator with it's shell.

2. Next disconnect all the plumbing and electrical to the engine.

3. Disconnect the intermediate shaft from the output flange of the transmission.

4. Attach a hoist to the lifting eye on top of the engine and lift the engine and gearbox out as a single unit.

5. Thoroughly clean and inspect everything. This is a good time to replace all of your brake and fuel lines if you haven't done so already.

Flywheel, starter and bellhousing problems and solutions:

Rules to remember:

1. 360 V8s are balanced externally on the flywheel.

2. 318 V8s are balanced internally on the crankshaft.

3. You can not use a 360 flywheel on a 318 or a 318 on a 360 because of 1. & 2.

4. 61-68 flywheels were .375" thicker so that they would clear the front flanges on the hydraulic bellhousing.

5. If you can not find one of these thicker flywheels you will need to install a .400" spacer between the crank and the later 318 flywheel. This is also true if you are installing a 360 V8.

6. It is very difficult to find a 360 flywheel since most of the later 360 engines came with automatic trannies. Because of this it is much less expensive to install a 318 than a 360.

7. 61-68 and the later engines used different starters and ring gears. The 61-68 ring gear had 172 teeth, the LA series engines had 143 teeth. Therefore if you are using a late flywheel you will need to change its ring gear to a 172 tooth one.

8. There are two types of early starters, one has the solenoid mounted on the starter and the other is remotely mounted. The remote mounted version is the one to use since there is less interference with the original steering box. This type was used on Chrysler cars between 61-68.

Flywheel installation:

Note: With the flywheel installed you will not be able to install the bellhousing because the front flanges on the bellhousing will hit the two dowel pins at the lower corners of the block. You can either install the bellhousing first and then install the flywheel and clutch or you can modify the dowel pins as follows:

1. Tap the dowel pins out in the flywheel direction.

2. Grind off most of the tapered end so there is only 1/16" of taper left.

3. Check the inside of the holes to make sure there is no ridge that will keep the pin from passing all the way through.

4. Tap the dowel pins back in from the flywheel side with the tapered end out until 3/16 is sticking out.

5. You should now be able to install and remove the bellhousing with the flywheel in place.

For 61-68 flywheel:

Since the starter ring gear is correct and this flywheel was designed for use with the hydraulic bellhousing you can bolt it directly to the crank flange.

For 69 and later flywheels:

1. You will have to remove the 143 tooth ring gear and install a 172 tooth one. If you have an oxy-fuel torch this is easy to do by supporting the flywheel at its center and heating the old ring gear until it drops off. Note that there is a flange on one side of the ring gear if this flange is on the floor side when you heat the ring gear you will be waiting a long time for it to drop off!

2. Flip the flywheel over so the flange is down. Clean the area of the flywheel where the new ring gear will seat. Note that one inner edge of the new ring gear is chamfered, this edge will face down toward the flywheel.

3. Place the new ring gear on the flywheel and heat it until it expands and drops on. Do not get it red hot or you will loose the heat treat that hardens the metal. With gloves on both hands rotate the ring gear as you push down to seat it. If it has already contracted you can use a hammer and drift to seat any places that have a gap.

4. You will need to install the .400" spacer plate between the crank flange and the flywheel as shown below. Be sure to use the 7/16"NF bolts and split-loc washers provided with it and check to make sure that none of the bolt ends stick out far enough to hit the rear of the oil pan.

 Front mount installation:

The mounts are shipped with their rubber pads and spacers attached. It is suggested that you leave them that way to keep them from getting mixed up with each other. After installing the front mounts tighten the two bolts on one flange and measure the gap between the other engine flange and the mount flange if it is greater than .015"you should either cut shims from .010" shim stock or get in touch with us so we can make you a spacer to fit. Chrysler made some special engines for some of their trucks that had nonstandard spacing between the front mount flanges.



For 360 V8:

1. Attach the front mounts as shown below using the four 7/16"NF X 1-1/2" or 1-3/4" long bolts split-locs and nuts that come with them. The right mount flanges will go in front of the engine flanges the reverse of the left side. Tighten the nuts just enough that you can still move the mounts up and down.



For 318 V8:

1. Attach the right mount as shown below with the spacer provided between the front mount flanges.

2. Attach the left mount as shown below placing its spacer between the rear mount flanges.

3. After installing the right and left front mounts lay a straight edge across the bottoms of them and adjust them so that they are on the same plane and level with the engine (the straight edge should make full contact with the underside of both front mounts. You can now tighten the 8 front mount bolts.

4. Next hoist the engine into place using a sling as pictured below.


5. Once the engine is in place install the right and left rear mounts to the frame as shown below. Leaving their bolts loose.


6. Install the 5/16" thick by 2.5" diameter rubber disc between the bellhousing flange and the right rear mount. Install the 5/8" x 3.5" bolt with it's with it's 1/2" thick by 2" diameter rubber disc and 1.750" diameter washer from the bottom and install the lock nut leaving the bolt loose.


7. Place the 3/4" thick by 2.5" diameter rubber disc between the bellhousing flange and the left rear mount. Install the 5/8" x 3.5" bolt with its 1/2" thick by 2" diameter rubber disc and 1.750" diameter washer from the bottom and install the lock nut leaving the bolt loose. You can now go back and tighten the frame to rear mount bolts making sure that the end of the special nut fits up into the 1-1/8" frame mount hole.


8. Place the 3/4" thick by 2.5" rubber disc between the right front mount and the frame and install the 1/2"NF bolt with its 1/2" thick by 2" rubber disc and washer as shown below. Don't tighten it down yet.


9. Place the 3/4" thick by 2.5" rubber disc between the left front mount and the frame and install the 1/2"NF bolt with its 1/2" thick by 2" rubber disc and washer as shown below. Don't tighten it down yet.

10. Place a spirit level across the frame in front of the engine and level the frame from side to side. Then place the level across the rocker covers and level the engine from side to side. Once the engine is level you can tighten the mount bolts down. Do not over tighten at this time and remember to check them after 200 miles as the rubber will have settled and the bolts will have loosened.

11. Install your gearbox and clutch slave cylinder.

You will have to notch the tunnel as shown below for the NP435.



12. Bolt your clutch pedal assembly to the left mount bracket and install your clutch master cylinder as shown below.  Notice that there are two washers on each bolt between the clutch MC mount and the tranny mount ears. Refer also to the photo in step 6.



Throttle installation:

1. Drill out the spot welds and remove the pedal hinge and pedal where it attaches to the tunnel cover.

2. Drill out the spot welds on the pedal pushrod brackets and remove them.


3. Install the throttle assembly on the firewall as shown below by inserting the lower left bolt through the lower left starter pedal mounting hole. Note that the left upper edge lines up with the right edge of the oval hole in the firewall. It also lines up with the vertical right edge of the embossed area at the bottom.

4. Next drill a 25/64" hole through the firewall in the same position as the upper hole on the bracket.

5. Cut the ball off the end of the throttle cable and pull the cable out of the housing.

6. Push the end of the housing into the 25/64" hole you drilled in the firewall up to its flange.

7. Determine the length of housing you will need for your type of carburetor and cut the housing off at that point with a hacksaw.

8. Reinsert the end of the housing through the firewall and the throttle mounting plate and secure it with the clip and shim    washers provided.

9. Feed the cable into the housing, out the firewall end and through the small hole in the upper end of the throttle.

10. Replace the throttle return spring with wire to keep it from moving and install the cable stop (1/4"X1/2" setscrew with 2 nuts and a 1/16" hole) on the cable from inside the cab.

11. With the cable pulled tight and the stop against the throttle linkage, tighten the 2 nuts on the stop to lock the cable in position.

12. Determine the most comfortable position for the accelerator pedal. The throttle arm with the roller on it has been left a little long so that you can put a shallow "Z" bend in it if you want to move the pedal sideways. When everything is the way you want it secure the pedal with a couple of 1/4" bolts as shown below. This will get you 3" of extra leg room or will let you move the seat forward a notch or so for a more comfortable back cushion angle.

Waterpump, fan and pulleys:


Pictured below are an early steel waterpump ('61-'68, left) and a late aluminum waterpump ('69-, right).

The early steel one is .700" shorter than the later one but the outlet is on the wrong side. The aluminum one has the outlet on the correct side but is too long. There are two ways to get around this. You can either move the lower radiator outlet to the left side or you can purchase an aluminum pump from us that has had .600" machined off its nose then a new shaft and seal installed.

      If the V8 is going into a WM300 that has a 251 engine you can use the stock unmodified aluminum waterpump since your truck has an extra 2" of radiator clearance.

Below is a photo of the crankshaft pulley you will need to find off of an early '58-'68 Chrysler car with power steering. These also came on 273 V8s. These can be used with the shortened aluminum waterpump or the early steel one and will let you mount a power steering pump.

      If you don't want power steering you can use one of the easier to find single groove pulleys that came on most of the cars and all of the trucks. 

     If your truck had a 251 flathead you can install the late model pulleys that come on the modern truck engines using the unmodified aluminum waterpump.


Radiator and fan:

You will need to remove your lower radiator mount bracket and elongate the two holes to within 1/8" of the edge so that you can slide the radiator forward to get more clearance between your fan and radiator.

The original six blade fan does an excellent job of cooling and can be installed on the V8 even though the center hole is a different diameter.


If your V8 has not been bored more than .030" oversize and your radiator is in good condition your engine should run the same temperature as its thermostat. I would suggest starting with a 170 deg. Our most recent conversion ran for hours in 107 deg. weather with a 160 thermostat and never got over 175 deg. So if you have overheating problems it is probably your radiator that is at fault. Don't install the fan shroud unless you really need it, it's a pain to work around.


Battery installation:

You will have to move your battery tray outward a couple of inches to get it away from the exhaust manifold. As shown below and build a sheet metal enclosure for it. Other mounting locations include under the bed or on the upper right part of the firewall above the heater. There are some high tech batteries that are much smaller than standard ones but have the same amp ratings that are easier to fit into tight places, unfortunately they are 2-3 times more expensive.


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