360 Magnum, NV3500 in a P15 build thread

[Smokeybear]

Engine/Transmission swap in a 1948 Plymouth.

 

This is how I did it, the parts/techniques/procedures I will be describing may not be right for you, in fact they might not may be right for me but I did it anyway. These procedures should not be taken as gospel as different people have different needs/skill levels/abilities. Do not try this at home, I am a professional stunt person and I stayed in a Holiday Inn last night.

 

Ok, so the original flat 6 and three speed in my car was lacking the excitement I desired. The only thing that could quench my thirst was a V8 and more gears.  I played with the thoughts of an LS engine, a small block chevy and many other ideas but I really wanted to stay with a Mopar powerplant. So I looked around and found a deal on a 5.9 magnum 360 from a 98 Jeep Grand Cherokee.

 

 

I was told this was a solid engine and from the research I did on the web they seemed to be a reliable engine with good horsepower numbers. Base HP numbers were 319 at 4400 RPM and 424 ftlbs of torque at 3600. Good enough for me. I picked it up and tore into it to see what I’d have to do to get it fresh. I was pleasantly surprised to find it had VERY little mileage showing. The bearings were all in excellent shape, there was no sludge in the pan, the galley or under the rocker covers. There was even crosshatching still showing on the cylinder walls. I decided that it looked good enough to go ahead and run without a rebuild. I did however pop in new core plugs (freeze plugs) and add new gaskets. I also replaced the timing chain with a double roller just to be on the safe side. I bought an Edelbrock carb intake (part # 7577) and an Edelbrock 750 cfm manual choke carb (part # 1411) to get the fuel in.  Also added was a distributor and coil made for an original 360.

 

Once the engine was cleaned and put back together I put it on the stand and went in search of a transmission. Dodge only offered a NV4500 behind a 5.9 and that was in the Ram 2500 and 3500 trucks. Although it would be beefy, it was going to be a challenge getting it under the car with minimal floorpan work. So I started looking at the NV3500. They could handle the torque and were offered behind the 5.2 and the 3.9 magnum engines. Most of the trannys I found were nearly $1000 in used condition and came with no guarantee they were in working order (rebuildable cores is what they called them) so I broadened my search. On Craigslist I found a Dakota that someone had chopped most of the sheetmetal off of and was using it as a “fun buggy” It ran and drove and had the NV3500 I was looking for. I bought it and trailered it home.

 

 

 

 

My plan was to use most everything I could unbolt from the Dakota I saved the radiator, driveshaft, fuel cell (yes they had changed it to a fuel cell for some unknown reason), the wiring harness (even though I wouldn’t be using it I would need a few of the connections), the heater/AC unit from the dash and all the A/C components, The instrument panel and the suspension (It was airbagged and had a 4 link on the rear). 

[Smokeybear]

Now that most of the parts were here, I tore into the 48. I removed the hood and front sheetmetal to gain good access to where I’d be working. The flat 6 and 3 speed came out surprisingly easy. I removed the stock transmission crossmember and the clutch/brake brackets and pedals. While it was easy to get to, I rebuilt the front suspension and dropped the lower control arm bracket to the bottom of the control arms and used new Aerostar springs. At this point I was going to keep the stock steering so everything was cleaned and greased to be reused.

 

 

 

 

I sat the 360 between the frame and made marks where I was going to have to relieve the firewall. A wooden mallet made quick work of the passenger side firewall. Once the engine was set back in place I measured several times before making a set of engine mounts from some 3x2 box tubing and the original transmission mount bushings. Everything seemed to line up nicely, the magnum exhaust manifolds cleared the steering box nicely and had plenty of room on the passenger side. The crank pulley had plenty of room over the front crossmember and the distributor had about an inch of room to the firewall. 

 

 

[Smokeybear]

 

 

 

I pulled the engine back out and mated it to the transmission. I used a flywheel from rockauto that fit a Ram 3500 (The 360 is externally balanced so the one from the 3.9 would not work.) I installed the clutch kit that replaced the original clutch from the Dakota. One part I did have to buy to get it to work is the “pilot bearing housing”. It is a stock part that comes stock behind the automatics (Mopar Performance #312-P4876056AA).

 

 

I cut up the Dakota transmission crossmember and fitted it to the tranny and frame. I used the hydraulic clutch master cylinder and slave cylinder from the Dakota. The floor pan was a bit tight near where the shifter was to come up through the floor. After making the measurements for the shifter I cut the hole and again used the mallet to massage the sheetmetal where it needed to be.

 

 

I had pulled the brake master cylinder and pedal mounts from the Dakota so I installed them into the 48 after I had cut off the pedal ends and welded on tabs to mount the 48’s pedal pads to. I also used the starter from the Dakota. I then sat the engine and tranny in place for the last time. 

 

[Smokeybear]

At this point I started looking at the steering and decided I wanted the convenience of the modern power steering found on the Dakota. So out came the steering box and column. I ordered a cavalier power rack and pinion from rockauto and followed the instructions found on the web for the placement. I made up some rack mounts from the 3x2 tubing and installed it.

 

I also installed the steering column in the 48 by mocking it up where it looked and felt right and used the firewall mount I had saved from the Dakota.  Since I had the pedal mounts already in, it was just a matter of cutting the column strap off and repositioning it to get the correct angle. I used the Dakota lower shaft to connect the column to the rack and pinion. But I had to turn it “upside down” to get a tight connection on the rack side. The rack input shaft has a 17mm DD connection and the Dakota has a spline connection. 

 

 

I then fabbed a bracket that allowed me to reuse the 48’s original tie rods and connect them to the rack and pinion. I used a few pieces of flat stock, some bracing and cut off the end of the pitman arm from the 48 steering box.

 

[Smokeybear]

The spark that was the beginning of this project was a wiring kit from rebel wiring that my wife gave me for… Christmas… in…October. Since most of the fab work was done I started on the wiring. This was actually easier than I thought it was going to be since all the wires are marked ever 6 inches or so. I started at the rear and moved toward the front. I mocked up the Dakota Heat/AC box in the 48 and it seemed to fit rather nicely. So I decided to add it to the list of things to do. The only real modification I had to do to fit the box was to drill a few holes in the firewall to mount the box, remove a little of the bracing on the passenger side cowl area and drill a hole for the drain hose.

 

 

I then finished up placing the wiring. I soldered and shrink tubed every joint and end I made.  By the time I had them all in place the only thing remaining that hadn’t been replaced was the headlights. So I switched them to their 12v siblings.

I had some sheetmetal work to do on the doghouse where the battery once sat so I widened the inner fenders to clear the 360. I also had to relieve the bottoms of the inner fenders to clear the upper control arm mounts. I mounted the Dakota radiator and condenser in front of the 48’s radiator bracket. I made two lower mounts out of some scrap 3x2 and some flat stock. I then made a hole in the passenger side inner fender to route the A/C lines. I then sat the doghouse back in place.

 

 

[Smokeybear]

Wiring continued on the engine and front lights. Again it was very easy. I did reuse the Dakota’s main relay box. I rerouted a couple of wires in the back of the box to utilize all the relays. I used relays on the headlights, horn, fuel pump, A/C compressor, and fan. I still have an unused relay left over in case I add something in the future. I was going to use the Dakota gauges but I decided to go with the originals instead. I bought a 12v to 5v converter to use for the speedometer but instead used it to make the 48’s fuel gauge work. I’ve made a piece to go under the dash to house the heat A/C controls and mounted a set of aftermarket gauges. The ammeter, temp and oil gauge in the dash cluster were working when I pulled the 6 but they are ornamental now.

 

http://s210.photobucket.com/user/Smokeybear31/media/1948%20Plymouth%20Special%20Deluxe%20Business%20Coupe/IMG_0554.mp4.html?sort=3&o=2

 

http://s210.photobucket.com/user/Smokeybear31/media/1948%20Plymouth%20Special%20Deluxe%20Business%20Coupe/IMG_0555.mp4.html?sort=3&o=1

 

http://s210.photobucket.com/user/Smokeybear31/media/1948%20Plymouth%20Special%20Deluxe%20Business%20Coupe/IMG_0556.mp4.html?sort=3&o=0

 

I’ve driven the car several times now and it is a BLAST!!! The 360 has plenty of HP and torque and I mean PLENTY, enough to keep me happy for many years to come. The 5 gears make my left foot and right hand happy and cruising comfortably at highway speeds is no longer a problem. The power steering is tight and responsive even though I did lose some turning radius, it’s not enough to complain about. The power brakes are outstanding! Even better than my wife’s Lexus. The temp gauge stayed a bit low, at 130-140 but it was cool out and I haven’t put the hood back on. I expect it to be good once the weather warms up.

 

 

Other small problems I had to overcome:

I drove the car on a short trip and found the water neck was seeping. After re-reading the instructions that came with the 7577 intake, it mentioned that the magnum waterneck would not work but an older style would so I bought a chrome on and replaced it and no more leak.

It was a bit of a chore to get the Dakota multifunction switch to work with the LED taillights and the aftermarket wiring harness. But once again the interweb came through and I found the pinout and wiring diagram of the Dakota and got everything to work. I disabled the airbag and the antilock system with no problems while I was at it but using the stock instrument panel it won’t matter anyway.

The speedometer housing on the Dakota is a pulse type but older style mopar gear output housings will fit in place and I have one of those ordered. Once it comes in I’ll update this thread.

 

I want to thank a lot of people here for the support and information they provided me in this endeavor. I hope to one day have the opportunity to help someone in the way you guys have. If you have any questions, please ask. I will do my best to provide the info I’ve gained with this project.

Edited January 8, 2015 by Smokeybear

[Don Coatney]

Good job and thanks for sharing the details. What steering wheel did you use? If you need to pull the radiator must the doghouse be removed? What differential / driveshaft did you use? Ratio? Disc brakes? Wheels?

[YukonJack]

Do you have a better picture of the bracket from the rack to the pitman arm?

[Smokeybear]

Good job and thanks for sharing the details. What steering wheel did you use? If you need to pull the radiator must the doghouse be removed? What differential / driveshaft did you use? Ratio? Disc brakes? Wheels?

I used the Dakota steering wheel. The radiator can be removed from under the front. I would have to get the car up far enough to clear the ground and tilt it forward. The brackets I made unbolt from the 48's radiator support. I used an Explorer rear end that I put in when the car was first bought. 4.10 gears 31 spine shafts. I cut the front 12 inches off the Dakota shaft and cut the front yoke off the 48's shaft. I slipped the Dakota yoke over the shaft and marked it in the correct spot, then took it to a local driveshaft place to have a new tube made. It was done the next day and cost $150. I do have disk brakes on the front and drum on the rear. The fronts are Rustyhope's kit and the rear are the factory Explorer brakes. The wheels are stock 48 Plymouth. I widened the rear wheels to 8 inches with hoops from Speedway

[Smokeybear]

Do you have a better picture of the bracket from the rack to the pitman arm?

I'll get some this weekend.

[falconvan]

Excellent job! These are the best kind of builds in my opinion. Fabricating all your own mounts, brackets, steering rather than buying bolt on stuff takes some real ingenuity.

[jcmiller]

Thanks for posting all the details.

[fstfish66]

interested in  rack  bracket pics my  self for a friends  project,,,looking good  so  far,,

[oldodge41]

Very nice. i love the do-it-yourself jobs.

[SonomaJim]

You've earned all the above complements.  Your documentation and photos are a great help and inspiring.  

 

Now that I'm retired I will begin assembly with similar modifications to a '46 D25 business coupe I've been accumating parts for and had in storage for 10+ years. PlyDo disc brake conversion, Intrepid/Concorde center pull rack, Sebring convertible seats with integrated belts, Magnum 360 and A518 tranny, '71 Dodge Coronet 8 3/4 rear end (same 47" spring perch and 62" wheel spacing as the D25). A California car, only the floors and trunk have limited rust through. Everything has been removed from the body shell and the shell has been soda blasted. All the sheet metal has been acid dipped, neutralized and primed. Chassis is in the side yard. First order of business will be assembly of the suspension on the chassis.

 

I have and am planning to use 3" drop spindles in the front suspension rebuild. You used new Aerostar springs in yours. How much drop did that give with the stock spindles? How much of that drop was due to repositioning the spring buckets on the lower arms. Can you comment on the advantages/disadvantages of the these alternatives and specifics about the springs? (The drop spindle instructions require modifiying and swapping sides for the steering arms.) 

 

After lurking on the forum for years, this spring I'm kicking my wife's PT Cruiser out of the garage for my bizzy.

Thanks for your insight.

[Smokeybear]

You've earned all the above complements.  Your documentation and photos are a great help and inspiring.  

 

Now that I'm retired I will begin assembly with similar modifications to a '46 D25 business coupe I've been accumating parts for and had in storage for 10+ years. PlyDo disc brake conversion, Intrepid/Concorde center pull rack, Sebring convertible seats with integrated belts, Magnum 360 and A518 tranny, '71 Dodge Coronet 8 3/4 rear end (same 47" spring perch and 62" wheel spacing as the D25). A California car, only the floors and trunk have limited rust through. Everything has been removed from the body shell and the shell has been soda blasted. All the sheet metal has been acid dipped, neutralized and primed. Chassis is in the side yard. First order of business will be assembly of the suspension on the chassis.

 

I have and am planning to use 3" drop spindles in the front suspension rebuild. You used new Aerostar springs in yours. How much drop did that give with the stock spindles? How much of that drop was due to repositioning the spring buckets on the lower arms. Can you comment on the advantages/disadvantages of the these alternatives and specifics about the springs? (The drop spindle instructions require modifiying and swapping sides for the steering arms.) 

 

After lurking on the forum for years, this spring I'm kicking my wife's PT Cruiser out of the garage for my bizzy.

Thanks for your insight.

First, thank you and everyone else who have looked at my thread. I am grateful and lucky to be a part of this site where so much knowledge is shared so frequently. Second. When I first got the car I cut a coil and a half off the original saggy springs and that dropped it about 3 inches. But every once in a while it would bottom out so I knew I'd have to address the situation at some point. When I decided on the swap I did the research on the aerostar springs and they seemed to be getting good reviews so I tried it. I knew I didn't want to cut them and be in the same boat so I moved the lower mounts to the bottom. The stance is just right in my opinion as it lowered the car another 1/2 inch or so but it doesn't bottom out anymore because the springs are progressive.

 

I'm happy with the way they turned out. Now you already have the spindles so its really a matter of taste on your part. The aerostar springs are good so if you use them and the drop spindles you may have the best of both worlds except having to deal with the steering rods. Here are some pics of the control arms on my car. They are bolted together with grade 8 hardware and welded. The only thing I didn't think of when moving them was to swap the upper braces side to side to retain a place to bolt the factory sway bar. But I'll be using one from a Jeep anyway so it doesn't matter.

 

 

On that note, I've reworked my steering since the last time I posted. The bracket I made looked and drove OK but it just didn't give me the warm fuzzy feeling I get when I looked at it. So I dug out the cavalier inner tie rods that I bought when I bought the rack. I studied on it and saw that the female side was so close to the male ends of the tie rods from the 48 but it was a bit too short. So I married them together with some threaded tubing and now it looks much better and it much easier to align.

 

I also found the rack was leaking from behind the boot so I sent it back to get a new one. When I get the rack back on I'll post up some more pictures. 

[wayfarer]

Great Photos and details!  Thanks for taking the time to post the info.

 

.

[fstfish66]

so you removed the  rack  bracket you made ? and  installed the  cavliere tie rods ?  in your pic thats what it look like,,but  looks like a bad angle on the  outer tie rod,,,i was really liking your  made bracket ,,,,do you have  better pics  of it showing  the  original pit man arm you cut off ??  thanks,,,

[YukonJack]

Angle might be better if the tie rod would fit in the arm from the bottom, nut facing up.

[fstfish66]

usually that  full conversion using the  cavliere tie rods  requires swapping the  plymouth  steering arms  from side to side,then  reshaping the  straight arm,or  heating and bending of the cavliere tie rods to  meet the  steering arms in the  correct angle,,, will be interesting to  find out  if he has steering  issues now,,,,thats why  i  liked  his  original idea  of the  made bracket,,,

[YukonJack]

usually that  full conversion using the  cavliere tie rods  requires swapping the  plymouth  steering arms  from side to side,then  reshaping the  straight arm,or  heating and bending of the cavliere tie rods to  meet the  steering arms in the  correct angle,,, will be interesting to  find out  if he has steering  issues now,,,,thats why  i  liked  his  original idea  of the  made bracket,,,

I bought this kit several years ago and never installed it. Been awhile since I read the instructions but I don't remember anything about heating the steering arms for installation. The dropped spindle uprights require heating and bending the steering arms though.

[Smokeybear]

Sorry guys, I've been a bit busy lately. The angle you see is because is it not hooked up to the rack in that picture, it is perfectly horizontal now that it's hooked up. The cavalier tie rods are way too small for the original tie rod ends. But adding that extra tubing works perfectly. I'll get a better picture of the bracket now that it's off the car. It may be this weekend before I can get back to it. 

 

 

I didn't have an issue with the steering other than the rebuilt rack leaking. But I could see the bracket flex when I had my son turn the wheel while it was the ground. I tend to over-build things and I just didn't like the flex. This way has NO flex and is as strong or stronger than the original would have been.

[Smokeybear]

Angle might be better if the tie rod would fit in the arm from the bottom, nut facing up.

 The steering arms are tapered so it won't fit in that direction. As said above, in that pic, it's not attached to the rack, it now sits level.

[fstfish66]

I bought this kit several years ago and never installed it. Been awhile since I read the instructions but I don't remember anything about heating the steering arms for installation. The dropped spindle uprights require heating and bending the steering arms though.

yes correct using a dropped spindle   requires  swapping  the  steering arms from  side to side and  reshaping  the  straight  arm to match the  factory  curved arm,,   then the kits include the  threaded adapters  to go from the  GM  long tie rods to new tie rod ends,, if you have an  older kit the  instructions call for  datsun  tie rod ends,,  very  small and  hard to find now and  you need a shim on the  stud of the  datsun tie rod to  fit the  factory  steering arm,,,now you use a ford explorer 2004  2005 tie rod  end it has the  same  metric  thread as the encluded in the kit  adapter threaded pieces but the  ford  tie rod fits the  mopar  steering arms with no  shim or  bushing adapter,,

my car  is  up in the air  now  doing  a gas tank,,,I  can  get  pics of the  installed  rack  if any one  is  interested,,,  i had pics during the  swap but the  card in the  camera went bad,,,,last name here should be  murphy,,,lol