Cummins to 727

[Plumber]

Does a Cummins bolt up to an 727 torque flight transmission? Is there an adapter kit if they don't bolt up?

[Chris Olson]

The Cummins to 727 was factory on the 89 and 90 Dodge trucks I believe it was in the non intercooled ones.

[Plumber]

Trying to gain MPG and pulling power

Do you think the intercooler cummins would cause a problem? My truck is all time 4x4, I love the fact that it is all time 4wd. I been using my truck to pull an 6,000 lb backhoe. She does fine on level ground but going up steep hillls I'm afraid it will not make it plus only get 3mpg while towing. Whis is why I was thinking of a 12V cummins that is turbo.

Any thought?

[JimmieD]

Any Cummins 6BT will give you all the pulling power you need. You wouldn't have to have intercooled, just the turbo.

Mine's only the 4BT, same engine but in 4 cylinder. It's rated at 105 hp and about 350 torque. Mines maybe 115-120 hp now. It easily pulls 6,000 lbs, so any 6BT would be more than enough.

They're heavy engines so think about a serious spring upgrade. The Cummins will bolt right up to the 727 with the stock Cummins Dodge adapter plate. You'll want a HD trans cooler and hopefully a trans temp gauge, and a pyrometer gauge to monitor exhaust heat.

[Desoto61]

Make sure the 727 is set up for a diesel. They are high torque, low RPM so the torque converter and valve body tuning of the transmission may be different than with a gas engine.

[Plumber]

What I found

Found an 90 250 with cummins 100HP injectors, turbo charged kit, hooked onto an 727. Now once I buy that what would be the next step? Hire a good swaping man? I also need to put a under the bed fuel tank and take out behind the seat one.

[JimmieD]

Found an 90 250 with cummins 100HP injectors, turbo charged kit, hooked onto an 727. Now once I buy that what would be the next step? Hire a good swaping man? I also need to put a under the bed fuel tank and take out behind the seat one.

No idea what you're planning on putting this in??? Seem to vaguely remember that you have a mid-70's truck? Plumbers carry heavy tools, so I'll guess it's at least a D/W-200? Because you inquire about 727 boltup I'll guess it's a 727 equipped 360 W-200, late 70's?

Several things are needed regardless of what truck: motor mounts located to frame, matching 6BT motor mounts on engine. First thing to do is crawl under a CTD and check out the factory mounts, they're excellent, try to copy them if possible. If not possible:

Can't cut or weld on the frame without going nuts gusseting, so it's easiest to fab up a box that slips into the channel, bolted against vertical face or wall of frame and also bolted at top. I made something like an old-fashioned sugar scoop without the handle.

This was a box formed from 1/2" steel plate, sized to slip in frame with a tight fit. At end of scoop where handle would fit the top and bottom are coped or rounded to snug up to the upper and lower curves as frame channel changes from vertical to horizontal. Roughly 6" wide disperses load and allows room to fit engine motor mounts to frame mounts. Bolted at rear to pull tight against frame, bolted at top to resist downward twisting load, with sides of scoop tapering downward towards engine with a lip sticking out for clearance. No funky welds here, but serious deep beads for ultimate strength.

Stock Cummins mounts are angled as I recall, so you may wish to build this scoop-shaped box and where sides are angled down weld a plate to accept stock CTD mounts. Engine gets a plate-steel fabbed mount bolted to block. Between these two you can either use stock Dodge Cummins mounts or fluid-lastic mounts.

You must have very heavy duty springs to handle the weight of a 6BT. They're at least 900 lbs, stock V8 is 600 lbs. so you need more spring and HD shocks, at least 1 ton rates here, more is better.

Fuel tank requires larger fuel line to feed injectors, plus a return line. Current fuel line is about the right size for return line so you only need a new fuel line for diesel. Bigger is better again, 3/8" is nice, 5/16" absolute minimum. For high performance an electric pump at tank pushing fuel to Cummins lift pump is best.

Diesel doesn't need much cooling, stock radiator should be fine. You REALLY want the largest & best tranny cooler you can lay your hands on, plus a Tranny Temp Gauge to monitor events towing etc.

Exhaust should be at least 4" out of turbo & all the way back, low restriction. If you're going to work that Cummins you MUST MUST MUST install a Pyrometer to measure EGT's Exhaust Gas Temperature under load. Takes about 5-10 seconds at overheat to melt pistons and destroy engine. Best to install a Boost Gauge as well, to monitor turbo output to engine.

Wiring is fairly simple, with a hot wire to fuel solenoid to allow starting/running, plus whatever is required for grid heaters or whatever. You want real heavy duty wiring to diesel starter and a serious battery, or two. Diesels don't much like cold weather so plan on using the stock Cummins block heater or other if in a cold area.

REG did a swap detailed in the PWA forum last year with lots of info.

[Plumber]

Jimmie

There is a picture of my dodge in the for sale section. I was going to sale it but I found this 90 250 with cummmins with no reverse. $2000.00 It's 4wd as well.

Back to my truck 77 power wagon full time 4wd think I could possibly get 13-14 MPG with doing this swap?

Oh yeah! When you coming to Indy to help me??? J/K

[JimmieD]

Sure, J/K, you buyin' the diesel fuel? I can be there pretty quick, with wrenches :~ )

You should be able to hit about twice that on mileage! I think average Cummins 6BT 4WD is about 20-23, drive it right and hit 24-27. The power difference can't be compared, unbelievable.

[Plumber]

Swap soon hopefully

I'm going to buy the 90 this weekend and part out what I'm not going to use. I was wondering could I get lucky enough to not have to relocate mounts??? I have a friend that is a wonderful welder (he can weld razor blades together by the razor edges with out damaging them) The guy that owned the truck before me took out an slant 6 and put in the 360. I'm going to take out the 360 and put in a cummins. The frames are the same from 74-93, SO mount swap should be easier?? (remember I'm no mechanic) I know the motor has to have at 7 degree pitch to the rear. I was going to use my 727, take out the torque converter and Fly wheel off the 90 since reverse is out in it. Some one mention to me to pull the Tranny out and mate it up then place the motor and tranny in together to help line things up easier. WHAt do you think???

Jimmy where you located at?? free room and board!! LOL

[MoparNorm]

... I was going to use my 727, take out the torque converter and Fly wheel off the 90 since reverse is out in it. Some one mention to me to pull the Tranny out and mate it up then place the motor and tranny in together to help line things up easier. WHAt do you think???

Jimmy where you located at?? free room and board!! LOL

I'd leave your trans in it's EXACT location, brace it into that position and mate the Cummins to it, that way you'll have nothing to re-do from the trans back and since you have to add motor mounts and reinforce the frame anyway, you'll be exactly at the starting point. There is no reason to remove your trans, just use the T.C from the diesel as it is most likely a HD unit. As mentioned above, you'll have to adjust the shift points in your trans to adapt to the Cummins power band.
There is no reason that a 1st Gen Cummins can't get at least 20 mpg, possibly more.

[JimmieD]

Hi Plumber!

Well, a bit too far to come a runnin', sorry, as I'm in California. This swap is just a different kind of plumbing for you. The 2 most important things are patience & patience, not necessarily in that order. Oh, and patience is important too!

Taking your time, studying the situation, comparing to a factory installation, it's not that hard. Using stock Dodge parts is easiest and the stock stuff is excellent. You'll have a fine truck when you're done.

[warlock440]

the cummins into any 72 thru 93 is a bolt in operation useing factory parts.The easiest way is to take everything from the donor and swap it into the recepient. I used a 93 and swapped everything into an 86..The frame in the 93 was broke by the previouse owner and poorly patched so I took everything (wiring,radiator,hvac,raditor support and intercooler,fuel tank and lines) and put it into the 86.
two things I noticed that are incorrect are #1 the V8 transmission will not fit with the Cummins and even if it would you still would not want to run the 203 T-case behind it, they had enough trouble with the chains stretching behind the V8s. If your donor vehicle is 4X4 you can use everything in your 77..
The second thing is the advice to put an electric fuel pump to push fuel to the engine.. Al the Cummins up to 98 1/2 had a engine mounted lift pump just like the older gas vehicles and do not need the electric pump. If you just have to have an electric pump then you should bypass the stock one so you dont break the diaphram and fill the oilpan with diesel..

[MoparNorm]

FWIW;
The 203 is a very strong case. The reason for chain stretch is wear, not torque. The 203 has a chain tensioner kit that can be installed along with a new chain. I wouldn't be afraid to run a 203 behind a Cummins.
All newer transfer cases are chain driven and seem to do just fine behind the 700 ft lb 6.7 Cummins.
The only case stronger than the 203 is the 205.