Dodge 440 to 5.9 Cummins Diesel conversion

Started by Wantawinnie, October 16, 2012, 12:28 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.


Worked on getting the exhaust downpipe fitted. I started with a 4" 2nd gen Dodge HX40 downpipe that came with the HE351 turbo I bought. The pipe did not clear the transmission because of the low mount 3rd gen manifold. I bought a 8" extension and started by cutting the flange off the downpipe. Also, in the top right corner is the 4" to HE351 turbo adapter flange which eliminates the Dodge factory cast iron elbow from the 3rd gen trucks.

Here is what I came up with. A 1.5" section was cut off the rear of the extension.

The downpipe needed to be angled in order to clear the spring hanger and transmission.

This is the adapter flange and downpipe bolted up the the turbo. The HE351 takes a special (aka expensive) oddball clamp and then a standard 4" clamp to bolt up the downpipe.

Clears the transmission.

Clearance from the spring hanger.

Ended up pretty good heading out the back.


The upper radiator hose was a little challenging. It has a short tight bend and goes from 2" on the Cummins to 1.5" on the radiator.

Wandered around the local parts store looking at all the hoses and came up with this solution. He had an ancient dry rotted hose on the shelf from a 80's F250 with an inline six. It had the right ends and a sharp bend so I ordered up a new one.

Cut the hose to length and added a spring to help with the bend.

Looks pretty good.

The upper hose inlet on the non intercooled 89-91 Cummins engines is different than the later versions. It is likely this hose will not work on those engines so check that before buying anything.


I wanted to update one of my previous posts about the Winnebago driveshaft as there is an error. The original driveshaft uses a 5380 series U joint and not a 1410. They are very similar but the cap size and inner C clip makes the 5380 unique. I will most likely have a new flange welded on the old driveshaft because a conversion joint from 5380 to 1350 is not available from what I can see.


Thank you for all the updates and photo's you are doing a great deed for all of us classic Winnebago owners who other wise would never have the b*lls to due a challenging experiment like this. Thank you... :)ThmbUp



Started tackling the lower radiator hose last week. I didn't get very far with any off the shelf hoses so it was time to dig in the Gates catalog and hope for the best. First pic is looking up at the space available. The radiator outlet is 1 3/4" and the Cummins is 2 1/4". There is also a bracket in the way making it even more challenging. If you have A/C on your Cummins this may not work for those applications. Also, I don't know if the non intercooled Cummins has the same outlet as the later versions so check that.

I needed a tight bend off the Cummins and found this hose which has a 2 3/8" inlet (close enough) and 2" outlet pointing down. One application for this is a 1984 F700 Ford with a 8.2L Detroit diesel. I ordered it and hoped for the best. Good news is it clears the frame and heads in the right direction.

Now it needs to connect up with the radiator. I found this hose with a 2 1/16" inlet (close enough) and a 1 3/4" outlet and what looked to be the right bends. Application for this is a 1964 Ford Galaxie with a 390 V8. This hose does not come with a spring. I pulled the spring out of the old 440 hose and installed it in the hose for support.

I test fitted both hoses on the Winnebago and they will work as is once joined together. I might take an 1" or so off the radiator inlet hose end once I get a stainless hose joiner ordered to put in. To join the hoses I will use the joiner and then clamp it with a Gates Powergrip clamp.


Got the 2" stainless splice to finish up the lower hose connection.

I left it apart a little bit just to show the connection. The two hoses fit together nice and snug.

The hose combination works fine as is and the clearance is good. Now I can get the thermal hose clamp shrunk once I find my heat gun.


Ordered up a Walker "Big Truck Muffler" and it came in.

Measures 37" end to end.

4" inlet and outlet with straight through chamber is supposed to sound decent and provide good flow.

Scored a lucky find at my local repair shop last week too. They were putting a new exhaust on a Dodge with an extended frame. Got a 8' long piece of 4" exhaust and the over axle bend. There are a couple rust holes from the hanger spots but the rest is solid. I only need about 6' of pipe so the holes can just be cut off and it will work great. I am going to run it out in front of the rear tire because the amount of bends are crazy to get around the axle, waste tanks, and shock mounts.

Couple shots comparing the 3" the Winnie had to the new 4" pipe going in. That extra 1" makes a big difference.


Next on the list is to mount the intercooler and start getting the intercooler piping figured out.

I had to cut out the front section of the crossmember to gain enough clearance for the intercooler.

I cut a new piece of angle iron to length.

I then welded the angle iron to the backside of the crossmember to make up for any loss in strength from removing the section in front.

I bought 3" mandrel bent pipes from Summit to make the intercooler runs. This is the turbo side pipe with a 45 degree boot off the turbo and a hump coupler at the intercooler.

This is the intake side with a 45 degree boot off the intercooler and a hump coupler at the intake connection.

This is the general idea for the setup.

Here is the final location for the intercooler. The lower mount is done but, I need to build a bracket to secure the top side mounts in place.


In order to line up with the forward facing intake I am building 4" needed to be cut off the intercooler connection pipe.

Test fitting the pipe and it looks pretty good.  Still waiting on a few parts I ordered in order to build my 3" intake horn so this is as far and I can get until that is done. Once the horn is built I can finalize all the pipe lengths and then weld some wire on the ends of the pipe to keep the boots from blowing off.

Fits nicely behind the grill.


>GRIN< WOW! Good work. Keep it up. You got us sitting on the edge of our seats. :)ThmbUp


So instead of asking a stupid question, I looked up on Google exactly what an intercooler was, what it did, and how they work...with a turbo, which yours is now going to have.

Not a lot of engine cooling provided though...its mostly to cool intake air to increase 02 levels when the turbo pushes the hot air. 

So you are going to run this without any sort of cooling fan at all?

I'd be

Kev and Patti, the furry kids, our 1981 Ford F-100 Custom tow vehicle, and our 1995 Itasca Suncruiser Diesel Pusher.


Hey Kev,

The intercooler helps keep the exhaust gas temps in check. It also does as you say to provide a denser air charge. Most diesels except the early one use some form of intercooling. It would have worked without one but stock power settings are a must then.

I am adding a couple electric cooling fans out front for engine cooling.


Whew!  Glad to hear you are going to use some electric!  I don't know much about Diesels but I figured that some sort of fan would have to be used, especially at idle in traffic on a hot day.  This project is so cool!  You've got me thinking about crazy stuff like this now for someday when the 454 finally gives up the ghost!

Kev and Patti, the furry kids, our 1981 Ford F-100 Custom tow vehicle, and our 1995 Itasca Suncruiser Diesel Pusher.


Diesels are perfect for these old applications due to their torque and excllent fuel economy. If the cruise rpm could be brought down to around 1800 at 60mph, I estimate 13 to 15mpg even with the flat front nose on the Chieftan. Don't believe me?......late 80's to early 90's Dodge's repeatedly achieved well over the 20mpg mark! As far as the concern for cooling....the ole Cummins won't heat up one little bit and if that radiator kept the bigblock cool, it will be more than up to the task of keeping the 5.9 cool. The 6BT will merely be loafing along while easily maintaining cruise speeds......Heck the chassis brakes amd steering will be the only limitation! It it were me though.....instead of adding the OD unit, I would simply change the gear set in the rear to 3.73. The 4.56 or 88's in your rig now will be way too low for that Cummins and with the low rpm torque you will now have, you won't have any problem getting that meager load rolling!


My '91 W250 4wd with the exact same engine gets 21-22mpg so I have no doubt about the fuel sipping capabilities of these engines. I am hoping for 12-14mpg with the Chieftain.

You guys would laugh at all of the speed vs rpm spreadsheets I studied before starting this conversion. I did include 3.73 gearing in my calculations and you still need an overdrive with those gears. 3.54 gears still don't work well and those are as high as you can get. A 727 gear vendor setup would be just about ideal with 3.73's. The 3.73's will also work fine with just the A518 overdrive transmission except for the large gap in rpm with the A518 overdrive transmission's 0.69 ratio when having to downshift. Others that have done similar or lighter RV conversions have found the Cummins will not pull some hills in overdrive and this will leave you shifting it down out of overdrive and then speed limited because of rpm's. That also could make passing an issue. 

Here are some of the values with the current setup using the gear vendor in combination with the factory overdrive, 33.6" tires, and 4.56 gearing. I also included a 7 percent torque convertor slippage in these values for more real world numbers. The larger tire size also knocks the 4.56 down to a 4.20 gear compared to a similar pickup truck with 31" tall tires. The Dodge trucks were available with either 3.54 or 4.10 gearing from the factory so it is not much deeper than original equipment offered.

Gear Vendor OD   45mph = 1713rpm, 50mph = 1903rpm, 55mph = 2093rpm, 60mph = 2283rpm
Factory overdrive 50mph = 1683rpm, 55mph = 1852rpm, 60mph = 2020rpm, 65mph = 2188rpm
GV + factory OD   55mph = 1449rpm, 60mph = 1581rpm, 65mph = 1713rpm, 70mph = 1844rpm

My situation is a little unique because I already had a 4wd diesel transmission and the Gear Vendor unit. It just made sense to use those versus the cost of rebuilding another transmission and then paying for a rear end gear swap as well. I will have lots of gearing choices depending on the road situations encountered whether it is hills, wind, traffic, or other factors.


After further researching I noticed that the 518 does not have a lock-up convertor. The weight of these rigs doesn't sway me a bit as far as the Cummins is concerned, but I understand why cruise rpm is so important. The ole workhorse could easily pull your load at around 1600 rpm but the slippage in the TC would send tranny temps kinda high. Not to mention, use what you already have - I missed that when I read through this originally.

Do you plan on modding your Cummins after the install? You can easily get 50 to 60 RWHP just by tweaking the pump a bit. Although, I'm sure you are aware of all of that if you are versed to tackle a project like this! I love this build and am anxiously awaiting the 1st ride and drive. I have a 97 12V with a 46RH 2wd tranny and I have often thought of trying something like this but the IC and inter-connecting tubing stumped me......NOW, thanks to your posts, I have options.

Thank for the extra work you are doing and letting us watch along with you! I am truly grateful!



I was concerned with using the A518 originally in this application. I am using a aftermarket torque convertor with a lower stall and less slippage to help with reducing heat buildup. I found a large factory Dodge frame mounted transmission cooler with a fan to go along with the one being mounted up front to help as well. I am also debating a deeper high capacity transmission pan to allow more fluid.

My plans for the Cummins are to get it running and see how it performs. If the need for more power is required and the exhaust temperatures are acceptable the fuel screw will be played with a little. Future power gain is the main reason for the big intercooler and larger turbo going in the rig. I wanted some room to increase it if needed. One thing about the early 89-91 non intercooled model Cummins is that the factory injectors are larger than the later 91.5 -93 intercooled models. I've read they are good to about 300hp if necessary.


Worked a little more on the intake today.

This is an exhaust flange I found from TTI exhaust. It is 1/2" thick laser cut with a 3" opening and holes 3" on center. Nice thing is it fits the Cummins intake without modification because even though the bolt holes are offset on the intake the larger bolt holes on the flange give just enough clearance. I wanted to keep the 3" intake diameter and it seems the only way to do that is build it. I eliminated the grid heater because there isn't enough room and this won't be driven in the winter.  I've never had trouble starting one of these down into the 20's without the grids on anyway.

To make the intake I ordered this 3" mandrel bent elbow with a tight 3" radius.

Here is the elbow without any modifications.

I measured 3" to be taken off the flange side of the elbow and about the same amount off the intake tube that will connect to it.

This is the elbow mocked up in place. Everything went together pretty well. I need to pick up some shorter metric bolts to secure the right side of the flange before welding it and the elbow together. Looks like it should flow pretty well. 


Hi folks, sorry for the lack of progress. The winter deep freeze has officially set in and below freezing temps along with the holidays have slowed down the diesel swap.  :(  With some luck and higher temps I'll get back into the swing here soon. 


i'm with you on that one, it  wasn't bad today here in eau claire hi 20s, been through your town many times, we call 61 the goat trail beats the heck out of my truck!! senic ride , just rough glad to see them fixing it.  like the pic beside the shed :D . i just reserved a camp site at otter lake by stanley wi. for a 9 day fishing trip in july. great project you got going.  can't wait till it in the 50s thats good working weather :)ThmbUp


I'm with ya. Freezing our buts off. We're running -5 -6 Celsius. Just getting over the flu and pneumonia. Getting cabin fever. Want to get out and work on the rig but that doesn't look like it's going to happen for a few months. $@!#@!


Had a little warmer weather yesterday so I got the exhaust system mocked up.(didn't last long, it's 6 degrees as I type this  $@!#@! )

I need a couple more band clamps for the muffler and some hanger straps to wrap it up. The free 4" exhaust pieces I picked up worked out quite well. This is pretty close to where it will end up once the hangers are added. I put a 45 degree cut on the tip similar to the 3rd gen Dodge Cummins trucks. 

The Walker Muffler worked out nicely.


Hey WW  Ya got the angle on the end of the tail pipe backwards . It will act as a scoop that way .  Increasing air pressure going in the pipe (wile moving) The leading edge should stick out farthest  Frank
"The Journey is the REWARD !"
Member of 15 years. We will always remember you, Frank.


That's how Dodge did it on my '05 Cummins. i?? The pipe face will be parallel with the body when done so there won't be a scoop.