5 ton gas to diesel/multifuel?

Does anyone know what all is involved in swapping out a continental gasser to a multifuel? Is it as simple as just swapping in the multi and multi components? (I.E. fuel system, wiring, etc.) The exhaust I would probably do differently than a std. truck anyway so that is not a concern.

I'm not positive, but I think I've read that the gasser tranny is direct, where the multi is an OD unit correct?

I am considering a 5 ton gasser that is for sale, but ultimately want a diesel. The multifuel should be the easiest swap as it is an OE engine for the trucks, although I may consider a conventional diesel also.

Ultimately I want something that can do about 60-65 with 52's under it.

You transmissions would be the correct one for use with the multi. The rest would be fairly simple, with the front motor mounting plate being different. The fuel system would need an axternal supply pump, and the installation of a return line to the tank. The wiring would be very similar, with an extension for the gen/alt and oil & temp senders being the only things to move. you would have to add a circuit for the cold start ignitor as well. The outlets on the radiator are in different locations as well.

To go to the Mack ENDT-673 Diesel, you would have to rebate the frame on the passenger side a bit to clear the fuel pump. The transmission is an OD unit, same case & boltup. Added to the previous work...

The real estate under the hood is not enough to run a Cummins NH-series or a Detroit 671. If you are going to use a commercial engine, I recommend the Mack 673 from a recent LTL series tractor. 350 HP with the same physical size block (albeit totally redesigned with very little commonality to the older ENDT) and their 9-speed transmission.

dg

That doesn't seem to be that big of a task, besides the physical removal and install.

Do you need to modify the frame for a non mack multifuel?

Also, anyone know how much room is needed for a bigger cummins? Like in the 8 series trucks? Or is it possible to use 8 series front sheetmetal on the 54 series truck?

I would proabably just do the multifuel conversion anyway since it's pretty straightforward.

An NH series cummins can be installed by moving the radiator ahead by about 7 inches.
New front motor mount needs to be fabricated.
Hood needs to be streched also.
If you have a winch, that makes things a bit harder, as the front frame needs streching.
A longer drive shaft for the winch needs to be made.
You won't be able to use an engine with a jake brake, as the engine will be too tall to close the hood with a jake installed.
This also rules out using an aftercooler. as the crossover pipe will be in the way as well.
Maybe some day I'll be able to figure how to post photos, then I can show you what I'm talking about.
An overdrive trans is desireable, as the top speed at governed rpm with 11.00/20 tires will be around 42 mph using a trans. with straight top gear.

I thought all the 5 tons had the same size engine compartment and hood?????

All I know is from direct experience.
My swap required the radiator and brush guard to be moved forward.

800 series trucks have a longer nose for sure. A bit uglier too in my opinion. Then again, I don't much care for the M35A3 either.

supermechanic said:

An NH series cummins can be installed by moving the radiator ahead by about 7 inches.
New front motor mount needs to be fabricated.
Hood needs to be streched also.
If you have a winch, that makes things a bit harder, as the front frame needs streching.
A longer drive shaft for the winch needs to be made.
You won't be able to use an engine with a jake brake, as the engine will be too tall to close the hood with a jake installed.
This also rules out using an aftercooler. as the crossover pipe will be in the way as well.
Maybe some day I'll be able to figure how to post photos, then I can show you what I'm talking about.
An overdrive trans is desireable, as the top speed at governed rpm with 11.00/20 tires will be around 42 mph using a trans. with straight top gear.

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If you send me the pics I can host them. nhfmp@hotmail.com

Recovry4x4 said:

800 series trucks have a longer nose for sure. A bit uglier too in my opinion. Then again, I don't much care for the M35A3 either.

Click to expand...

no truck deseves to be likened to the M35A3... that's just wrong

With all the work involved, wouldn't it be easier to just get a multifuel or diesel truck? Sounds like you want something reliable [60-65 with 52" tires]. A 5 ton with a 6602 is at least 45 years old. An 800 series is about half that age. Again, just my two cents.

lacoda56 said:

With all the work involved, wouldn't it be easier to just get a multifuel or diesel truck? Sounds like you want something reliable [60-65 with 52" tires]. A 5 ton with a 6602 is at least 45 years old. An 800 series is about half that age. Again, just my two cents.

Click to expand...

If I could find one close and that wasn't too expensive, I'd be all over it.

Besides, swapping in an engine isn't all that big of a deal, I've done it before, just never on a large truck.

98hd said:

I've done it before, just never on a large truck.

Click to expand...

On a big truck an engine swap is easier, lots more room to work with.
To put a longer engine in where a gasser was, the procedure I followed went like this.

1) remove brush guard and radiator.
2) remove old engine.
3) switch clutch parts from flywheel on old engine to the new one.
4) install new engine, they have a universal bellhousing, (I think It's an SAE #2, but don't quote me on this) they bolt right up.
5) weld tabs to front side of front crossmember, this is where the new front mounts will be attached. Locate tabs by assembling front mount in place, fabricate sizes to fit, weld in place while blocking engine to correct elevation and angle.(this way everything is self aligning, you don't need to worry about making fancy calculations and measurements).
6)Fabricate radiator mount using same procedure. Best to use low mounted fan in this swap, only minor triming needs to be done on fan shroud.
7) mount brush guard infront of radiator, brush guard location determines hood strech.
8 ) second hood needed for strech, cut a section from rear, near hinges, length depends on brush guard location. lay good hood in place over engine, measure gap at rear, cut other hood a bit longer to get an overlap to weld to. remove hinges on good hood , lay on top of cut section, and weld both together.
9) filler panels need to be fabricated at radiator sides, next to head lamps.
(head lamps will now be recessed behind radiator, but they work just the same)
10) a bit of fiddling will get the radiator hoses to work, if you've come this far you are almost there.

this is what I did to get a cummins335 to fit. if you want to put a 6-71 detriot in there , it should be similar. the detroit can rev a bit higher so you can get more road speed.
I don't know how the gear spacing in the tranny will work with a detroit as these engines have a very narrow powerband.
If this is your idea of fun, have at it!
Thanks, Ed.

supermechanic,

Stuff like that always sounds fun, my problem is finishing a project once I get started.