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6BT in E350 - 27' Winnebago

100K views 138 replies 44 participants last post by  edpruss 
#1 · (Edited)
As of this update (Dec 2021), I did this build 10 years ago. Figured I'd post some Bottom Line Up Front info in this first post for folks who find this thread and don't want to scroll through 7 pages of posts, challenges, updates and ultimate victory.
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Pre conversion (7.5L gas engine w/ 3 speed Ford C6 automatic transmission): average cost per mile: $0.56
  • embarrasingly slow on long mountain passes, hills, against wind, etc
  • 6.5 MPG average
  • Wolf Creek Pass (Colorado) at ~10 MPH
Post conversion (5.9L 12 valve Cummins turbo diesel w/ 6 speed Dodge G56 transmission): average cost per mile: $0.31
  • more than enough power for EVERYTHING!
  • Average high 13 mpg with a few tanks above 15. (just depends on driving conditions and my ability to keep my foot out of it)
  • Wolf Creek Pass at 55+MPH , passing quite a few cars on the way up

As for this conversion project - I sold it quite a few years ago. I really enjoyed it while I had it. I put about 50,000 miles on it before selling it. Once I got everything worked out it ran great. It has changed hands twice now since I sold it and last I heard it's still putting miles on the odometer and smiles on the owner's face. I've long since lost track of it. I expect the body of the RV would have given out by now so maybe the engine and transmission have been removed and are powering something else.

Some good engine bay and cabin photos of the build in progress in post #55

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Now, let's get to the original beginning of this thread. This was documented as I did the work - not once the project was completed. Had I known what I was up against..... Well, this project might have had a different outcome.
I hope this helps inspire others. At a minimum, it documents how I stuffed a 1st gen Cummins into an Econoline engine bay. Enjoy - Mark (edited Dec 2021)

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I've owned a few motor homes over the years and just have never been all that impressed with the power delivery. After spending a bit of time in Europe and seeing lots of great little campers with 2.5L turbo diesels and many with manual transmissions I just couldn't get the thought of building one out of my head. Nearly a year's worth of research and long nights with my friend Google, I finally convinced myself that I could do it. Through a strange set of events I stumbled across a suitable donor engine. A very good deal was made and the truck was mine (minus the original Getrag 5 speed manual).

Here's the recipient:
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A 27' Class C on a Ford E350 chassis. In it's original form it had the fuel injected 460 with a 3 speed C6 automatic, 3.54 gears and 30" tires. The price was right and the RV was in good condition. Of course a 450 chassis would have been much better. Or maybe I could have even found a diesel powered one but what fun would that be? The 1991 RV would allow me to do the conversion without needing to configure an OBD II interface to get it recertified so I could change the fuel designation on the title. The 1st Gen Cummins would be a straightforward swap without needing to mess with any computer integration.

Here's the Cummins out and ready to get torn down:
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It's a 1st Gen so all mechanical - easier for my brain to digest.

Although it was running when I got it I still didn't know what the 'noise' was until I got this far into it:
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Looks like the head gasket failed and leaked down for months finally wearing the piston skirts on #4. No problem.

Shiny and new:
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Everything else looked and measured fine so I put a fresh set of gaskets in and put it all back together:
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Engine ready - now I need something other than the Allison 542 that I got with the truck (wrong high gear ratio)
 
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#2 · (Edited)
After a month or so of research I finally found a G56 6 speed manual from an 08 Dodge Ram 3500:

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The gear ratios were what I was looking for with a .74 overdrive ratio and nearly 6:1 low! Awesome. Besides, I like a manual and I just didn't want another heat generating system. Yes, yes - I know that diesels are different, but I'm still a bit traumatized by hauling this RV all over the Colorado Rockies. Wide open at 30MPH going up some of these passes just isn't a good idea. Things tend to get hot.
 
#3 · (Edited)
Now to start tearing down the RV:

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That good old 460 is quite a beast!
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While removing the 460 looks simple in the photos, it wasn't. A friend from the Australian outback (literally) was in town for a while and he came up with an ingenious solution: Instead of trying to swap engines with chains - use an engine bar.
Here it is in action:
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Here is a shot of the empty engine/transmission bay. Here you can see how far back the Ford motor mount brackets are for the 460:
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I didn't know it at the time but the Cummins mounts sit very nicely on the cross member. You can kind of see that the passenger side angle of the cross member is correct but the driver's side is quite a bit off. I also discovered that the original position of the 460 was about 4 1/2 inches offset to the passenger side. Ever sit in an Econoline van? The driver's foot well is adequate while the passenger has almost no space. That's why.

Here's my Cummins on the way in:
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I had to pull the oil pan and oil pump pickup tube to get it over the lower front body cross member. The 'engine bar' turned out to be really great. It allowed for tilting the engine forward and backward to help navigate it into the engine bay.
 

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#4 · (Edited)
A little creative cutting of the floor pan and the transmission is now in:
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Not at all it's final position, but here's a rough idea of how it will look:
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Here's a challenge: I don't have enough room to make a 90* bend to clear the firewall/body to get to the air horn. I'd like to find an adapter to allow me to rotate the intake horn 90* to the front. Any ideas? I figure that an adapter plate would do the trick.
This is what I have:
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This is what I want it to look like:
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With the engine in it's final position my tape measure says that I have enough room to keep the OEM fan, have room for the Dodge radiator then AC evaporator then the intercooler in front of them. It looks like I have to carve away some of the back of the grill to clear the intercooler. I want to keep it all as stock looking as possible.

I've found a clutch/brake pedal assembly but it will take some creativity to link the hydraulic system to the setup I have. Then of course there is the wiring, cooling and air plumbing, exhaust, drive shaft.......
 
#6 ·
I keep seeing how the Ford 300/6 motor mount brackets are the answer for 4BTs. So I spent a few hours in the junk yard today and came home with a set as well as lots of other goodies. Guess what? They look like they'd be perfect for my build but in reality they don't work at all. If I could even get the engine on them it would sit way too high. Oh well - back to my original solution: Passenger side motor mount directly on the cross member; drivers side on a 2"+ fabricated motor mount bracket. I'll get some photos of that soon.

Lots, lots, lots to do but I'm really enjoying it.
 
#7 ·
Very cool! Motor mounts have been the biggest challenge for me so far by a long shot. Measure measure and when you think you have it right... measure again just to be sure. Should be an awesome rig when its finished!

Sent from my Droid using Tapatalk
 
#8 ·
JOZ: you da man! bounce

Great job on shoe-horning that motor in there.

It looks like your swap is going look just like it came that way. Best of all worlds.

Keep up the good work!

I'd love to do the same thing to a Lazy-Daze. I really like them, but their Ford V10 and Chevy 350 power trains suck for a motor home, so they have to be modded.

Randy
 
#12 · (Edited)
GreatShot - here are some photos of my motor mount solution:

Driver's side:
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The welds aren't pretty but very nicely penetrated the 3/8" mounting plate. I'm using about 5 or 6 inches of a 2x2 piece of box steel that came from a trailer hitch. Conveniently the right size holes were already drilled (for the hitch pin). If you look closely you'll see that the 2x2 steel isn't flat against the base plate. I shimmed the upper side with a piece of 1/4" bar to get the needed angle. I drilled holes in the base plate to align with the existing holes in the cradle that were used for the original motor mount brackets. If I was really bored I could have measured the angle differences and done some fancy calculations. Instead I just test fit it all until I was satisfied, tacked it then removed it for proper welding.
It isn't the prettiest but I don't know who will be looking at the motor mount brackets.

Passenger side:
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This couldn't get much simpler. I will make a plate to align the motor mount bolt in the correct position. Right now the motor mount goes through one of 3 huge (1 1/2" maybe) holes in the cradle. Alignment is kind of vague right now. I'll fix that.

I was also able to test fit the new transmission cross member I picked up from the junk yard. Just about perfect. I'll fabricate up custom mounting brackets so I can get it into just the position needed for my transmission but I'm really happy that it will work so well.
 
#18 ·
This project makes me Giggle! I love the ole Ford Motorhomes and with a Cummins and 6sp Stick, What an awesome Rig! Kudos to you for taking up the challenge and building what you want.

Ill be watching this.

The Swap that I did on my 89 F350 I was able to get every factory gauge working except for the Tac, I ended up with an aftermarket tac. That was the most frustrating part of my swap. I spent way too much time and effort trying to get it to work but to no avail.

Good luck and keep us posted!
 
#19 · (Edited)
Well, after too may other obligations I was finally able to spend a few hours on my conversion this weekend. I got the transmission cross member mounted. I had to fabricate brackets to drop the cross member a bit lower:
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Totally wrong yoke shaft so I can't actually test fit it. The yoke is from the C6 automatic but the distance isn't bad.
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Looking forward:
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And looking back:
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The carrier bearing sits just a touch to the passenger side. That will be easy to fix.

I had to cut the dog house to clear the shifter. I knew this was coming so no big deal:
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Then finally on to the radiator, A/C condenser and intercooler. Here's a silly but very effective way to test fit it all before I started welding:
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Intercooler mount:
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Only minor modifications needed. Overall, pretty good so far.


Today I also dropped the fuel tank. Plain steel - not galvanized. Good news there. Next on the list is to pull the gasoline fuel pump. I was very surprised just how much fuel was left in the tank even after I pumped it "dry". I might lengthen the fuel pickup line.

All in all - a very good weekend although filled with interruptions and distractions. I'm going to have to start taking days off from work just to get anything done! I'm pretty pleased with the progress so far.
 
#20 ·
Are you going to remove the old (gas) fuel pump from the fuel tank? I guess you need to locate a screen to cover the fuel pickup once you pull out the old gasoline pump. I just had to drop the rear tank, and I installed a screen on mine, the person who did the conversion in my F350 forgot to install a screen meaning any sort of crud could be sucked in. I'd rather screen it at the tank.
 
#21 ·
I have 2 donor tanks from a diesel F350. My plan is to graft the pickup tube and a screen from one of the donor tanks onto mine. I haven't even opened either of the diesel tanks yet so I don't know if this is even a realistic plan. I'm sure something will work out. All I can say is that a steel 30 gallon tank with 3 or 4 gallons of gas is BIG and HEAVY! I had to raise the back of the vehicle to get it out. I am very glad to see that the inside of the tank is very clean - no rust.
 
#22 ·
With the engine in it's final position my tape measure says that I have enough room to keep the OEM fan, have room for the Dodge radiator then AC evaporator then the intercooler in front of them.
You may want to rethink this depending on how hot it gets where you will drive and how much time you spend at slow speeds. I have the same air flow path through my heat exchangers (outside air --> intercooler -> condenser -> radiator) and the A/C system is not as efficent as it used to be without the intercooler in front of it when sitting in traffic. Once I am moving, the cool air comes back out of the vents.

Of course, this means a lot more work on rearranging the AC tubing, so it may not be worth it for your application.

I really like this swap. You are making really great progress, fast too. Keep up the good work!

CR
 
#23 · (Edited)
Hi Joz,
Nice work ! That will be fun to drive.

My Dodge donor vehicle has the air cond heat exchanger first in the air stream. It bolts to those four fasteners on the front of the intercooler.

I will have to do some more research (on this site) about fuel tanks and fuel pumps. Why do you need a diesel tank ? Is there a reason why a gasoline tank can not be used for diesel ?

Can the gas fuel pump be used or is the 6BT lift pump all that is needed ? The long inside the frame (plastic) tank from my Dodge may be installed in the RV. Then I plan to switch tanks by turning off one tank pump and turning on the other same as my Ford F250 (gas).

Keep up the good work,
Peter
 
#24 · (Edited)
My tanks have the gas fuel pumps removed but the previous owner didn't put a strainer filter on the fuel pickup. I have been having a lot of problems with them. Right now I'm still fighting an air leak I guess but only from the rear tank.

I dropped it, removed the sending unit but can't see anything wrong. The front tank seems fine. Both sending units don't work, one pegged max and one pegged minimum.

I used dvm to check the readings while moving the float unit and it's changing as you move it so might have an open/short on each.

You also should knock out the "unleaded" barrier on top of the filler tube if you use gas tanks if you ever get to a pump that has the larger diesel nozzle you'll understand why. If I could just solve this stupid air leak in my fuel lines my truck would be perfect.

I use the mechanical pump on the 6BT but on the rear I have to turn on the electric lift pump otherwise it's starving.
 
#25 ·
The Dodge D250 with 6BT that is the donor for my swap has the mechanical lift pump on the engine and also an electric fuel pump in the tank. I looked up the electric fuel pump replacement for this Dodge on rockauto.com and discovered that it is exactly the same pump and level module (Bosch 67611) that is used in the 5.9L gas engine Dodge D250 for 1992 (and other years). Maybe the mechanical lift pump needs a lift for a long distance high lift system. I plan to keep the electric fuel pumps in both tanks and use a switch to change tanks (and change fuel level gauge electric source also).
 
#26 ·
I wish I could do what Joz did and use original diesel fuel tanks from a Ford... I have oddball problems with the rear tank, now even with electric lift pump it's still starving. I need to look at the original Ford diesel sending unit, pump assy to see what I can do to make it work. I'm almost ready to put one of those big, ugly, all-space-consuming truck bed tanks with a transfer pump in it.
 
#27 · (Edited)
I chose to put the intercooler first in the air stream as I could mount the AC condenser above the body cross member. It was simply an issue of space. Even so, I've had to cut away a significant amount of the grill to clear the intercooler. My goal is to have it looking as 'stock' as possible from the outside.
As for the fuel tank - I read somewhere that sometimes Ford galvanized the insides of fuel tanks (gas). Apparently, diesel can dissolve that coating, turning it to goo. Not good for the injection pump or injectors. I removed my in-tank electric pump but still have another on the frame rail. CedarTree: thanks for sharing your experience. I might have hold onto the in-line pump until I'm confident that the lift pump can pull enough fuel.
For the fuel filler, I have a single filler, selectable dual output fuel neck out of an Australian Land Cruiser. It allows you to fill two separate tanks, and fill them individually, from one filler neck. However, in the spirit of just getting this thing back on the road I might skip installing it and the dual tank setup until later. I plan to use the existing 30 gallon gas tank plus the 35 gallon fuel tank that came on the donor truck. The donor tank mounts inside the frame rails and I have plenty of room for it.

So here are a few photos to show where I have gotten so far:

Original fuel tank sending / pick up unit:
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Pump removed & diesel pick up screen installed:
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Venting the tank with low pressure air:
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Here you can see where I've begun cutting away some of the excess depth of the grill. This is to clear the intercooler.
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If it turns out that the AC condenser is just too hot being so close to the radiator then I'll have to come up with a different solution. I just don't have the space with the components I have on hand. I'd likely have to get a smaller intercooler that would sit against the radiator then put he AC condenser in front.... I'll wait for the results of the 'real-world' test.

So my grand plan of fabricating an adapter plate to clock the intake elbow 90* when up in smoke. I made a template only to find that the bolt pattern difference isn't great enough for the bolts to clear each other. However, with the template, I could easily see just how close the bolt patterns are so I marked the intake elbow and got out the file.....
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I took off just enough from the base plate on the intake elbow and now everything fits just fine.

One of the (other) big changes to my vehicle on this conversion is the automatic to manual transmission swap. I was lucky enough to find a manual Econoline van in the junk yard. I came home with the factory clutch/brake pedal assembly. Here I have the new & old assemblies in one shot:
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#28 · (Edited)
The instrument cluster and steering column needed to be removed to swap out the pedal assembly:
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The instrument cluster needed to come out so I could correct the fuel gauge:
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Oh, and having the automatic shift lever and gear indicator on the steering column just wouldn't cut it so they had to go:
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Sorry. No photos of the finished product but I'm impressed. There will certainly be photos of the steering column once it gets reinstalled.

Finally, for this installment is the exhaust system. I'm dealing with very tight space constraints. I had to cut the original down tube and 'bend' it (without use of a bender). It looks rough but fits perfectly:
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I was able to piece together a bit more of the original truck's exhaust system, reweld the muffler and it should all work pretty well until I can get a real exhaust system under it.

Today I dropped off the radiator for some 'slight' modifications to make it better fit my application. Last night I ordered a pile of intercooler plumbing.
With any luck I'll be able to get all together and fire it up this weekend. I'm still a ways away from moving it under its own power but that will come....
 
#29 ·
Hmmmm..... Good thoughts on the in-tank fuel pump guys. My tank is still out so now is the time to figure it out. I'll keep digging around to see what I can find out. It would be easy enough to just put the original pump back in. Of course I still have another fuel pump mounted on the frame rail. The original gas setup had 2 pumps.


Today I received my order from siliconeintakes.com! Awesome stuff. Not cheap, but exactly what I needed. I don't have any photos as I was installing it all well after dark. For intercooler pipe I'm just using new 2 1/2" exhaust pipe - nothing fancy. I also got a new tensioner pulley and a Dodge voltage regulator. Kind of like Christmas!

I have been trying to figure out how to solve the issue of the recently realized problem of space between the oil filter and the air intake hose. Everything fits okay but I won't be able to change the oil filter without removing the air filter to turbo plumbing. I figured I'd try Google since I seem to rely on information on this site too much. 30 seconds later I find myself back on 4btswaps with lots of discussion regarding relocating the oil filter. It might just be safest to modify the air intake tract instead of messing with the oil filter......

I'm still on track to start her up this weekend so a solution to the air/oil filter issue just might have to wait.
 
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