Diesel or Multifuel

[Jim Hunter]

Hello guys,

I like to hear your opinions which engine is most preferred for very long distances and also about reliability ?

Thank you,

Jim

 

[cattlerepairman]

I understand your question, but in this forum you are really asking "2 1/2 ton or 5 ton".

Stacking up my two cents: the Multifuel was never designed to be particularly long lasting and indestructible. It has other qualities that were important for the military at the time.

Having said that, it is an engine design that will last, if not abused, and allows you to rebuild it without too much fuss (unless you destroyed it and have big chunks missing from the block). Sleeved cylinders etc.

Longevity simply means that you have an engine that is not being run at its design limit all the time. See the debate about the CAT 3116 and max rpm on this forum.
Someone else pointed out that the engine in the White farm tractors (similar design to Multi) was governed at 2200 rpm load speed. When you run it at 2500 instead, what does that mean for engine life?

I'd say that it is not so much a debate about Multifuel or Diesel (or Gas), but on how close to its technical limit the engine has to perform in the application over prolonged time.

According to at least one poster here, the CAT 3116 in an M35A3 can be revved to make the truck go 60 mph. Sure. For how long - compared to running it at 48 mph - that is the question re longevity....

 

[Robo McDuff]

Cattelrepairmen, you are absolutely right. I drove with an old VW "hippie" van 5000 miles to the Sahara and back to the Netherlands with an out of line flywheel. No prob. My late brother had that car a few hundred miles and wrecked the engine. His engines blow up, my engines last. The highest I had on a private car with a 1.9 liter diesel engine was 472,000 km (about 300,000 MILES), with about 130,000 of those mine.

The main difference was driving style and maintenance. Every 10,000 I put in new oil, oil filter, fuel filter, air filter, nothing else. I shift gears early and stay about 5 to 10 % below max possible. Certainly in towns, he was always at high revs, shifting late etc. As said, my engines lasted.

 

[Jim Hunter]

Forgive my ignorance but there is no 2 1/2 tons multifuels ???
I am almost certain that both trucks was 2 1/2 not 5 tons...
Either way thank you both for your answers...

Jim

 

[Danger Ranger]

You all got me very confused. Both the 2.5 tons and the 5 tons had multi fuels. Early ones (both maybe?) had gassers, am I right? Other 5 tons had the Cummins diesel (M817...etc.). The M35a3 had the CAT diesel, and I do not know about the other newer 5 tons...

I too am lost on the vaugue question. Maybe you would like to share what kind of truck you are looking for, or more info behind the question..........

 

[cattlerepairman]

Forgive my ignorance but there is no 2 1/2 tons multifuels ???
I am almost certain that both trucks was 2 1/2 not 5 tons...
Either way thank you both for your answers...

Jim

US - production M35 are either Gas (petrol) or Multifuel. There is no ''Diesel'' in the lineup. Sometimes you see ''Diesel only'' written on the fuel tank, but that is not because there is a Diesel engine in the truck.

US-production 5-ton trucks are Gas (petrol), Multifuel, or have a Mack or Cummins Diesel.

In the US, none of these had an automatic transmission - all are 5 speed manuals.

Only the ''old'' Deuces and the ''extended life'' Deuces (M35A3) have automatic transmissions.

Recognizing that you are in Greece, you MAY have some variants over there that differ in some details. There are Norwegian M35 variants that came with singles and lockers from the factory. There were M35 trucks with Cummins diesel engines and surely other oddball combinations.

If you can actually get a 2 1/2 ton with a ''real'' diesel engine, I would say ''go for it''!

 

[Jim Hunter]

Sure guys I will try...
The trucks I was looking to buy was both 2 1/2 tons.
They are both multifuel and diesel.But the diesels does not have auto transmission !
I will be in the yard in 10 days or so and I will try to get as many details and pictures from them...

Jim

 

[91W350]

Those in the photos would appear to be M35A2 trucks and more than likely are multifuel powered. They may be marked diesel only. Look at some of the engine threads on this site and you can learn to identify the engines pretty quickly. The dual upright oil filters and narrow valve cover make the multifuel pretty easy to pick out. Glen

 

[M543A2]

Let's address a couple of things. First, there is a diesel engine in the "multifuel" trucks, it is just adapted by the injectors and a fuel density compensator in the injection pump to give it a multifuel capability. The trucks with "DIESEL ONLY" on the tank have the fuel density compensator locked out so only diesel should be run in them. Without the density compensator, the pump cannot regulate the amount of fuel injected when fuels other than diesel are put in them. It now becomes what it originally was, a purely diesel engine.
The second point is that of the 478 engine used in the White 2-155 tractor. This is the engine used in the trucks, minus the military fuel system. When looking closely at the farm tractor engine, one finds ordnance numbers cast into parts. I have attached a specs page from Implement and Tractor manual that shows that the RPM in the tractor high idle is set at 2,370 to 2,420 RPM. The 2,200 RPM mentioned by another post is the rated RPM, which means it is the RPM the engine should develop full power at, economically and for hours at a time. When running silage blowers, etc. The engine will hit the top RPM a lot of the time with no problems. 4,000 hours on these engines and still going strong in a well maintained tractor are common. Incidentally, if you find one in a scrap yard, you can get the filter base assembly off it for the screw-on filters.
As was mentioned by one individual, the key is how the engine is treated by the operator and how it is maintained.
We find that the internal parts in these engines are much heavier than are in the Deere and other makes of farm equipment engines engines of similar displacement. We have several of them we have been running for many years with turned up fuel, diesel only, and drivers who know what they are doing and care about the equipment. we have no complaints whatsoever about them. One big key to long life with turned up fuel is to have the right head gaskets in them (separate fire ring type with weep passages) and let it warm up before demanding power. Investigation of an engine on a test stand with a heat gun will show you that the interface of the block to head at the back of the engine gets hot very quickly. If not allowed to normalize, this is where the old style gaskets fail.
Long life comes from good maintenance and using common sense, which sadly seems to be not too common at times!!
Regards Marti

 

[Flyingvan911]

The 2 1/2 tons usually have the LDT Multifuel with puts out about 135 horsepower. The 5 tons had the LDS Multifuel which has about 195 horsepower. The engines are the came except for a few differences. The search box will answer those questions.

If you are looking to buy a deuce, try to find one with the LDS. It has more power and it makes a big difference. Every deuce owner with a LDS loves it. I sure love mine!!!

 

[emr]

It is NEVER just a Diesel only engine, this is all covered so many times in this site it is absolutely ridiculous, the multi capability in IN the DESIGN of the motor not the compensator, read and search these trucks U are asking about and then make a list of questions , U really are confused, not a big deal , but U really need to read alot here, more good info than U can get on one thread of a question that does not really make sense, sorry all due respect intended, as for the question, they are apples to oranges, the diesel motors are better than multi fuels, but remember a multi is a diesel engine, but with that said a multi is a GREAT motor that has alot going for it too, please try the search and go from there. my 3 cents, good luck.

 

[JasonS]

There is ONE thing which makes it a multifuel: high compression ratio. The rest is just embellishment.

 

[Jim Hunter]

Thank you all guys for your great help

I will let you know when I will go back to the yard...

Jim

 

[AGE|kshaufl]

The ones pictured in your post are all M35A2's. All M35A2's were shipped with either a Continental, White, or Hercules motor. All are Multifuel capable. The FDC's may be bypassed and the fuel tank marked diesel only but that is not the end of it. They are still multifuels by nature. The pistons, compression ratio, and spray pattern of the injectors makes them a multifuel.

If they have a true diesel only engine in them it is an after market modification.

The multi's are great engines if taken care of properly.

My two also.

If they weren't great engines they would not have lasted over 40 years.

 

[Jim Hunter]

Thank you...
If it has an diesel engine conversion I will not bother with it...
Gassers are out of the question for running costs...
So a nice multifuel w/w it will be just ideal...

Jim

 

[197thhhc]

On our latest project we thought about an engine swap for more power. A 6bt cummins or even a detroit engine. But with fuel over $4.00 per gallon and the ability to run alternate fuels in the multifuel we couldn't justify the change over. I love the multifuel and am planning to swap one into a chevy 3500 pickup later this year. Just so I can run free fuel.

 

[Flyingvan911]

Let us know how the swap into the Chevy goes. People will wonder what kind of engine you've got when they here it.

 

[M543A2]

Well, here we go again, look on the side of the motor (multifuel) and it will say "liscenced by MAN". This is the German company that developed this style combustion chamber (ball in piston, off center single or 2 hole stream NOT fog injector) this ball chamber looks and is about the same size as if someone had cut about 1/4" of of the top of a golf ball. this system was developed for use in submarines due to the shortage of crude oil in the war. This company also worked VERY closely with Rudolph Diesel and even produced his first engine! they use a virtually solid stream of fuel sprayed off-center to create swirl, onto the interior surface of the ball shaped combustion chamber in the piston. then as the injector opens more fully a small amount of vaporized fuel is injected at the right time to ignite the main charge coating the combustion chamber. This allows the use of HARDER to light fuels like gasoline to be used due to the fact that with fog type injectors all of the fuel would be in the cylinder in a dense fog BEFORE ignition could occur due to the retarders (used to be tetra-ethyl lead) to create high octane fuels (why your truck says "no av-gas") then when it did light due to the elevated temps later in the compression stroke and the closer proximity of fuel molecules to each other it DETONATES like a bomb and does damage. In a "Multifuel" the fuel burns, not explodes, off of the surface of this chamber in a controlled manner assisted by the GREAT amount of swirl induced by the way the air entered the cylinder through the valves in the first place. This swirl being intensified many times over by the compression and squeezing of the mixture into a smaller diameter area (The "ball" chamber in the piston) most other Diesel engines burn the fuel just as it is injected in a FOG into the toroidial (half of a doughnut) shaped "open" chamber or use indirect injection where the injector sprays into separate a chamber in the head with only a very small opening to the cylinder. (early 6.9 and 7.3 fords) also most other early "Diesels" Cat Cummins Perkins etc. Contential and others used a different system called the "Lanova" cycle where the fuel was shot across a figure "8" chamber into an "energy cell " with a very small venturi opening and a flat top piston with two small side streams of fog to light the charge with the rest burning "outside" the chamber in the energy cell and then injected by it's own force over time into the cylinder to prevent knock. These engines can be identified by large plugs in the cyl head opposite the injectors and were used prolifically by Case, Minneapolis Moline, Massey Harris and others. The point is that ALL of these engines were and are called "Diesels" because the ignition of the fuel charge is by heat of compression only. (we can discuss all of the Allis-Chalmers and Monarch dozers built with "semi -Diesels" and spark plugs but no carbs later) as a matter of fact some of Rudolph's engines sucked a mixture of coal dust and air in and then lit it with compression and are "Diesels". We have Fiat engines with the MAN "multifuel" style combustion chambers that have 17:1 CR and were not intended for multifuel use, but used this design in a purely Diesel fueled application for the reason that all Diesels are limited by destructive "knock" and while being less fuel efficient and dirtier they will make more power with less knock allowing those higher compression ratios for better starting. To summarize, the engine IS a Diesel if it is compression ignition. I have built and dynoed over 300 Diesel engines of many different makes including these and will say that next to a Perkins they are one of the best engineered engines out there and DO NOT suffer from the catastrophic failures as much as many brand X when turned to 4500 rpm and 600+ hp with multiple turbo's in tractor pulling. I will refrain from making this "book" any longer and not go into a comparison of all the major components of these engines that lead me to this conclusion except to say that they have as stock many features available only at great expense in the aftermarket world to other Diesels. However I have on my bench a hammer head that was broken in half by a truck "driver" so nothing is idiot proof!!!

 

[M543A2]

My father and I after alot of measurements got rid of his 1993 Dodge Cummins 350 4wd due to the fact that we could not readily get a multifuel to fit, we had built up the cummins in our own shop from the ground up to about 450 hp (ported head, injection work, turbo work,5" exhaust, 160 H.P. 2-stage home grown L.P. kit, balanced, ARP fasteners, reduced compression etc.) It got very good fuel economy and would beat the later model mustang cobras. However, being that it was a single wheel truck and we haul my 1975 Massey Ferguson 1155 to shows etc. and it weighs 14,000 lbs, this was very dicey with a tri-axle bumper hitch trailer! (tail wagging the dog) after we built the multifuel engine for my M-35 (ported heads, combustion chamber mods, gasket matching, custom adjustable governor springs, internal pump work, GOOD head gaskets, custom tuned exhaust, trial and error power timed injection, (doesn't end up anywhere near where you think it would) and 3300 rpm red line, we wanted the power of the multifuel in the Dodge as well, especially the bottom end torque. Fuel economy would have suffered but not a great ammount as the M-35 gets 12-15 empty. We have a 20 ton air brake trailer that we pull now as well as other trailers and often use it to move mobile homes and tow bar other deuces or 5 tons. (no down shifting for hills) and have in 8 years never hurt anything. Part of the longevity was oiling mods as well as a control in the cab that I can use to limit maximum boost when loaded to about 15 psi, (5-9 is stock and where it is set the rest of the time except for when showing off!) it will make enough to peg a 30 pound gauge but, this is not good on engine for more than a few seconds (1 pull up through the gears empty) I had a 2008 Dodge Cummins that thought he would pass me in a double yellow and leave me sit, I let him get around and then I pushed him up to about 75 mph letting off to keep from hitting him! (runs 62 in 4th and goes from 25 MPH in third to 67 mph in fifth in a measured 7.0 seconds) perhaps next I will put that propane kit from the Dodge on it and a home built aftercooler with multipoint water injection and custom mapped turbo (pipe dreams$$$$) However the rest of the drive line will need attention as the clutch has about all it wants right now. Got tired of split cylinders, blown head gaskets, and cam/lifter troubles and poor port flow with the Cummins (using the marine gaskets and Hasley's tourque specs on ARP studs helped alot but didn't seem to cure gasket probs). These engines were an economy engine designed by International harvester and Cummins to replace the more expensive 466 ci in their farm equipment, however, they are very impressive and tough engines and the probably the best engine ever put in a pickup.) 359 ci at 15:1 to 17:1 just can't torque down low like 478 ci (turned up) and 21:1 compression.

 

[JasonS]

None of the MAN embellishments are required to make it a multifuel. They may make it easier, but they are not required.