1967 Travco 270 440 to Cummins 8.3 Upgrade

Interesting idea but it reads like shoe horning a Corvette C4 power train into a 1972 Vega. You'll turn heads but it will have a bit of a Frankenstein Monster if it comes alive.

You might be better off finding a late model low mileage GM diesel pickup to use as a donor. And you'll need the entire truck to make the conversion. Fuel system, engine/trans electronics, gauges, antitheft and such. An insurance auction truck that was tee boned would be a perfect donor.

CamaroMan wrote:
So absolutely no way the M300 or whatever will hold up? beef up the front end / add stiffer springs?

The motor will not be working anywhere nears its full capability/quite the opposite.. cummins 5.9 is a common swap, and the 8.3 is only 500 lbs more.. tranny is 150 lbs extra..

What are your plan for the bearings, brakes, tires and wheels, steering components? Gas engines aren't real heavy, they hang of the vertical section of a frame and mmounts. You're into a heavy engine, they're mounted from the

Physically the 8.3 and Allison is much larger, the weight is spread over much more of the frame. The engine is 48" high, the turbo sits next to the valve cover on the right. The rattling mechanical injector pump sits high on the left of the motor. Measure 48" up from where your mounts would be, that's how much the motor will intrude into the motor home. That is also the noisiest hottest part of of an engine. When I said you'd have to make a new engine cover I meant one that would make it tolerable to ride next to for more than a few miles at a time.

When you're talking weights you haven't added in the radiator, intercooler,trans and oil coolers. You've got to find room for those also, they're big, heavy and need a lot of real estate in an area that normally is relatively small in a gas engine vehicle. You've got to plumb them with big hoses that don't like tight bends. Then you have to fill everything with a lot of gallons of oil, antifreeze, and tranny fluid.

You need a very large air cleaner and very large tubing that will feed the turbo. Remember, that's on the top of the engine, so it will add to the intrusion into the motor home.

One last thing that really bothers me. How long since that engine ran? Just from the picture it looks like it's been parted, you're looking at some big bills for valuable pieces that are missing. The turbo is gone, that exposes the inlet, exhaust, and lube system of the engine Are those sealed up really well?

CamaroMan wrote:
So absolutely no way the M300 or whatever will hold up? beef up the front end / add stiffer springs?

The motor will not be working anywhere nears its full capability/quite the opposite.. cummins 5.9 is a common swap, and the 8.3 is only 500 lbs more.. tranny is 150 lbs extra..

wolfe10 wrote:
8.1 Chevy/GM engine-- yes.

Cummins 8.3/ Allison transmission-- NO WAY. Would way overload the front suspension. And, enough torque to do real damage (more than twice OE torque).

Beef up the springs and go for it! Besides, according to another thread on this forum, the switch to diesel fuel will make the rig handle better! ;)

So absolutely no way the M300 or whatever will hold up? beef up the front end / add stiffer springs?

The motor will not be working anywhere nears its full capability/quite the opposite.. cummins 5.9 is a common swap, and the 8.3 is only 500 lbs more.. tranny is 150 lbs extra..

wolfe10 wrote:
8.1 Chevy/GM engine-- yes.

Cummins 8.3/ Allison transmission-- NO WAY. Would way overload the front suspension. And, enough torque to do real damage (more than twice OE torque).

Haven't factored in the tranny just the engine weight difference..

Wow, only 1000 pounds difference between:

Chrysler/Dodge 440 and Torqueflite transmission

AND

Cummins C 8.3 engine and Allison 3000 transmission.

Thanks for the replies - I was a little concerned about the weight - not so much torque/etc.. its 1000 lbs over the 440 in there currently.. Not sure the M300 chassis can handle that, but there is 12 inch i beam between the front rails which I thought was insanely overkill at the time.. not even sure if the tire ratings would hold up.. bear in mind this is a light weight motorhome (14500k gross original, 12500 when we are done with complete overhaul), not a drag car..

fwiw - this is a C8.3 - mechanical, no elec required. Currently have a 440 in there -


Torque would only be harmful if we over used it, for RV cruising I would hardly be tapping the throttle.. even IF we had say 700 ft lbs on tap we would use half that or a little more..

I have the complete frame rail available and the motorhome is currently stripped..

Mixed opinions here -

We can refab an engine cover if need be. I own a marine repair shop.. this is a project and aware of some issues.

We have a member here who is going on 5 years rebuilding a class C. It is
a never ending project and when you are done, the RV is worthless.

If you like to tinker, then it’s for you. If you like to camp and travel,
buy a decent used one. You will save money and time in the long run.

You need to stick with a gas engine.

From the picture what you don't have is going to cost thousands of dollars and you're looking at thousands of hours of fabrication. There's nothing about that chassis that was made for an engine and trans that size- you need a new one. You'll lose a huge amount of floor space to gain minimal accessibility to do maintenance. Good access with room for the sound and heat insulation to make sitting next to an old mechanical diesel for hours on end would mean an engine cover would be too big for seats.

8.1 Chevy/GM engine-- yes.

Cummins 8.3/ Allison transmission-- NO WAY. Would way overload the front suspension. And, enough torque to do real damage (more than twice OE torque).