Engine Transmission Upgrade Suggestions

[mackattack2]

Hi

I'm new here and new to macks, but not new to truck restorations. It has been a hobby of mine for years. Recently I purchased my first Mack truck. It's a mack LJT sedan cab fire truck. I would like to upgrade the engine and trans to something more up-to-date and dependable. As for the engine it has now, a big 707 cu in gas engine, I think it's too far gone to try to do anything with. The truck's been sitting in a field with no spark plugs and the manifolds and starter in the back of the truck for 16 years. This brings me to my question. What engine/transmission combinations do you recommend?

I do eventually intend to drive this truck, not just to local parades but cross-country too. I would like to upgrade the engine/transmission to a later mechanical diesel drivetrain. My first priority is dependability. I want an engine that wil last hundreds of thousands of miles between rebuilds. My second is economy. I'm not looking for the biggest engine I can stuff under the hood, but something very economical I can drive on a regular basis. Someone told me (a non-mack person) I should consider a cummins 5.9 as they are used in everything from Dodge 1 ton trucks to school buses to Ford F800's. But I've still got a lot more research to do before I decide on anything. What are your engine/transmission combination suggestions? For a transmission I want a manual, with really low low gears and very high overdrive with lots of powerband overlap so there is no possibility of lugging the engine between shifts. From what I've read, I don't want a twin-stick trans, but I do want at least 6 speeds or more. What are your suggestions and opinions on what I should be looking into? I won't be racing to any fires, but I might be occasionally pulling an airstream trailer.

And if you have any suggestions on where I can purchase parts manuals and shop manuals for this old truck, it would be appreciated.

Thank you.

Steve

[Packer]

How about a Cummins 'B' series (Dodge) with an automatic transmission?

Get an older model with manual fuel, rather than electronic, and don't look back!

The older engines are 180-200 hp and fuel consumption is 10+.

That's what's going in my 'EG'. Done my home work (and own a 2004 Dodge) and for most playing around,

this might work!

Packer

[GearheadGrrrl]

Or if you want to keep it a little closer to purebred, ex-Postal Service Macks are going for less than $5000. They give you a 300 horse Mack engine, Allison automatic, and a bunch of other good stuff to swap into your classic Mack.

[vanscottbuilders]

I have a good 673 Mack diesel, normally aspirated, with new fuel injectors and fuel pump tune-up. I also have a good direct drive (10 speed) transmission to put behind it.

I am using a 711 and a triplex transmission in my truck, so I will not be needing these parts.

If I got $1,500.00 for the engine & transmission I would be happy, and you would be well on your way to converting to diesel power.

The engine came out of a running truck, recently. It was changed for more power, as the truck is being used on the road to pull fairly heavy loads. The duplex came out of my own truck, and was operating fine when removed.

You are welcome to pick up the parts, or we can arrange delivery at a reasonable cost.

Contact me through this website if interested.

Thanks,

Paul Van Scott

[mackattack2]

How about a Cummins 'B' series (Dodge) with an automatic transmission?

Get an older model with manual fuel, rather than electronic, and don't look back!

The older engines are 180-200 hp and fuel consumption is 10+.

That's what's going in my 'EG'. Done my home work (and own a 2004 Dodge) and for most playing around,

this might work!

Packer

hi Packer,

Thanks for the reply. Can you tell me any more details about this engine? What years were they used in Dodge trucks? How is a 'B' series any different from any other series? Is it turbo-charged? What year did they start to use the electronic fuel injection? (I definitely don't want electronically controlled anything) Were they also available with a manual trans? Will the newer NP 6 speed bolt up to them? How would I recognize the proper engine if I saw one say at a wreking yard?

Thank you for your opinion, it is appreciated.

Steve

[mackattack2]

I have a good 673 Mack diesel, normally aspirated, with new fuel injectors and fuel pump tune-up. I also have a good direct drive (10 speed) transmission to put behind it.

I am using a 711 and a triplex transmission in my truck, so I will not be needing these parts.

If I got $1,500.00 for the engine & transmission I would be happy, and you would be well on your way to converting to diesel power.

The engine came out of a running truck, recently. It was changed for more power, as the truck is being used on the road to pull fairly heavy loads. The duplex came out of my own truck, and was operating fine when removed.

You are welcome to pick up the parts, or we can arrange delivery at a reasonable cost.

Contact me through this website if interested.

Thanks,

Paul Van Scott

Hi Paul Van Scott,

I'm still new to macks. Pardon my ignorance, but is a 673 Mack diesel 673 cu in or how big is it? Something from a modern cement truck, for example, would be too big to fit in the narrow L cab type engine compartment. What year and about how many miles are on it? Does it have the starter, alternator, flywheel, etc? Does the trans have the bellhousing, clutch, etc? What would be needed to install it in my truck?

And anything you can add to help educate me is appreciated. As a shade-tree mechanic my only experience has been with light and medium duty gas-engined GM trucks.

Thanks.

Steve

[mackattack2]

Or if you want to keep it a little closer to purebred, ex-Postal Service Macks are going for less than $5000. They give you a 300 horse Mack engine, Allison automatic, and a bunch of other good stuff to swap into your classic Mack.

hi GearheadGrrrl,

That's definitely something I will look into. But any idea where I would find an ex-Postal Service Mack? I've watched for old Macks on eBay for years, and I've never seen one there. Any idea physically externally how big a 300 horse mack engine is compared to a 707 cu in gas Mack engine?

Thanks for the suggestion.

Steve

[GearheadGrrrl]

The Postal Service Macks can often be found on eBay and truckpaper.com, search under "Mack" and "MR688". The Mack engine block was the same size for decades, but the accessories mounted to the engines vary. Thusly I'd eyeball and measure pretty closely before buying an engine, and you'll need to check your rear axle gearing and how that will affect top speed, etc.. You'll also need to look into driveshaft compatability, changing to negative ground, etc..

[Packer]

The 'B' series Cummins is what they put in Dodge trucks for their diesel.

Yes they are turbo'ed, and I THINK the manuel fuel system was good 'till about 1988.

My 2004 has a 6 speed transmission but a 'baby quad' will bolt up to it, as per my guy-next-door Cummins rep.

I've played around with both 4 and 6 cyl engines (the 4 cyl turbo'ed is about 125 hp and are used in delivery vans)

As far as what to look for, a "Dodge Cummins" should get you going.

My engine came with an auto and even though it ain't truckin' with only one stick, I'm going to try the auto, and if I don't like it, I'll put the quad box in.

Buy the way, the 'EG' I have had a 150 horse gas flat head 6 engine. I don't think the springs would take a large 673, and that is part of the reason to go with the Cummins.

One 'B' model will have a 170 hp and the other a 237 Maxidine. I like Mack drive trains, but the 'EG' will be like a large tired pick-up and shoe horning a bigger engine in is not what I'm after.

You got the room, and the UPS 300 hp with an auto might make quite a ride!!!

Packer

[Rob]

My 2004 has a 6 speed transmission but a 'baby quad' will bolt up to it, as per my guy-next-door Cummins rep.

Hey Packer, just remember you will have to have an SAE flywheel housing to bolt to the engine to use the "baby quad" in the same size. I would assume the small quadraplex would have a SAE #2 housing.

Rob

[Packer]

Hey Rob!

I guess if money is no object, I could put a TRQ722 in, but that is a little overboard. LOL

I do have what I think is all the right stuff for the switch, except pilot bearing and maybe clutch disc.

Time will tell!!!

You going to make the big show in Colorado? I'm working on the time off as we speak!!

Packer

[chris88]

Mechanically injected cummins stopped getting put in trucks half way through 98. Dodge had a inline bosch "P" pump from 1994 till 1998 and before that they had a bosch rotary pump. That was 1988-1993. The P pump is the best because you can turn it up very easily, cheaply, and reliablely. All you need is one wire going to the fuel shut off selonoid on these motors to make them run. It would be very simple once you got it all bolted down and fitted right.

[Rob]

Mechanically injected cummins stopped getting put in trucks half way through 98. Dodge had a inline bosch "P" pump from 1994 till 1998 and before that they had a bosch rotary pump. That was 1988-1993. The P pump is the best because you can turn it up very easily, cheaply, and reliablely. All you need is one wire going to the fuel shut off selonoid on these motors to make them run. It would be very simple once you got it all bolted down and fitted right.

Hi Chris, you wouldn't know of a SAE flywheel housing laying around for one of these would you?

I could also use one for a 2.3 Ford engine also.

Thanks,

Rob

[vanscottbuilders]

MackAttack:

I thought that the Lanova diesel was available in the LJT. If it was - isn't it about the same physical size as the 673?

If so - a 673 or a 711 diesel with a duplex or triplex transmission would give you an all Mack drivetrain. (Or - a Maxidyne 237 with a straight 5 speed) And certainly if the 300hp Post Office power train would fit - the 673/711/237 engines would also, and they would fit much easier at that. I don't think that the Allison will just bolt in, though.

To answer your earlier question - the 673 diesel is indeed about that size (672 ci) and was offered in the B models, and other Macks, through the fifties and early sixties along with the big gas engines (the 707's, like you have). The diesel was preferred by many operators, although there were a lot of gas powered Macks.

I'm not really sure, but there may indeed be a weight difference, like Packer said earlier, between the gas and diesel power plants.

As the technology developed, the Maxidyne series of diesel engines replaced the older 673's and 711 diesels with new "high torque rise" powerhouse engines in the mid sixties. The new engines had a very wide power band, and could be effectively used with the straight five speed transmission for many applications. These engines are physically the same size, albeit only with the two valve heads (four valve heads increase the space required to install the engine). But, as Packer said, the accessories and "bolt-on" equipment, like turbo housings, aftercoolers etc., will increase the space necessary for the installation. As the horsepower goes up, you seem to get more stuff required to be bolted to the engine. In the LJT you will probably be short of space.

I looked at all of these possibilities for my B67 project (also a "space constrained" cab) - and I decided to stick with the old tried and true diesel.

While I cannot comment on the Cummins, which I believe to be a really good engine, I can say with some certainty that the 300hp Mack will be a difficult fit. And I'm sure that the Allison will challenge you even more.

As for my spare 673 - it is a complete engine less the generator and starter, which stayed with the original truck. I need to look at the bellhousing to see if the flywheel is there or not - I think it is, but, I'm old enough that I don't remember.

We all talk - a lot. And sometimes we take things for granted as for what may or may not work.

I would suggest, before you do anything, you should find out what the LJT had for engine options and front axle choices from the factory. Then you can figure out what will really work well for you. It may be as simple as beefing up the front springs and plugging in one of the Mack diesels.

Good Luck with your project -

Paul Van Scott

[b61fred]

Hi,

I would recommend the 673 or 711 because the weight and physical size is almost identical, the 707 likely had a adapter to make the smaller belhousing fit on the 67 series transmision, I think a 673 would be a almost direct bolt in for the 707, the only thing is the starter will be on the lower passenger side. There will be some work if you want to pump water with the fire truck part, there is some vacuum operated items like wipers and if you have hydrulic brakes the booster, there is a valve under the truck that has something to do with volume or pressure that is vacuum operated. diesels don't make vacuum like a gas engine. I have talked with charlie hatfield about this conversion with him. See if you can talk with him, he knows more about this, he wants to do the same thing with his l model fire truck. good luck

Fred

[chris88]

Rob, i dont have any cummins parts layin around. Any decent truck junk yard should have a handful of B series parts though.

[Rob]

Rob, i dont have any cummins parts layin around. Any decent truck junk yard should have a handful of B series parts though.

Hi Chris, I agree but $350.00 is a bit steep for a flywheel housing!!

Thanks,

Rob

[mackattack2]

MackAttack:

I thought that the Lanova diesel was available in the LJT. If it was - isn't it about the same physical size as the 673?

. . . .

I would suggest, before you do anything, you should find out what the LJT had for engine options and front axle choices from the factory. Then you can figure out what will really work well for you. It may be as simple as beefing up the front springs and plugging in one of the Mack diesels.

Good Luck with your project -

Paul Van Scott

Hi Paul Van Scott and Fred,

Thank you for your comments. I'm still trying to find some documentation to know what engine options were available for that truck. I have full air brakes, not hydraulic or air over hydraulic. And the windsheild wipers are missing completely so I'll just need to find or design an electric setup for them.

I have no intention of trying to make the thing pump water. In fact, I might take out the entire pump assembly. That would probably save a couple thousand pounds and open up a lot of useable room inside the cab. I could leave the control panel intact and if done carefully, no one would ever know the difference. And after I'm gone, if someone after me decides they want it to pump water again, they can put the pump back.

I'm not clear, is the 237 the same as an E-7 engine? And is the Maxidyne engine the same as the Mack 300 hp engine referred to in previous posts? Do the 673 and 711 and 237 physically all have the same external engine block dimensions? What kind of fuel economy or mpg can I expect with each respective engine, including the 673, in a lightly loaded truck? If a Chevy 350 gets 12 mpg, should I expect only 6 mpg with a 672 cu in engine?

My truck has a 5 speed, will that be a direct bolt up to any of these mack engines? Do the engines referenced above all use a no 2 bellhousing? I'm not really interested in the allison trans.

Fred, when you said "a 673 would be a almost direct bolt in for the 707" does that mean the engines use the same engine mounts? If so, that would sure make things easy. To me, the 707 looks unnecessarily massive, and that's with its manifolds and starter missing. Paul Van Scott, what engine and trans did you end up using for your B67 project?

Sorry for all the questions guys, but I'm trying to give myself a crash course education on Mack trucks.

Thank you for your help and a thank you to anyone I forgot to mention in this post.

Steve

[vanscottbuilders]

Steve,

The Maxidyne engines were available in several horsepower ratings, depending on turbo boost pressures and compression ratios etc. So the 300hp engine that you are referring to could be a Maxidyne. There definitely was one.

I don't know if the E-7 and the early Maxidynes are the same or not.

Your fuel consumption calculation is a little skewed - 1st you are comparing a diesel engine to a gas engine, 2nd- the gear ratio and engine speed (rpm) are not in the calculation and finally, the type of driving that you will be doing will have an effect. (Are you loaded or empty, on flat terrain or hilly etc., etc.)

The Macks are generally pretty fuel efficient. Depending on all of the above factors, if you were empty and being careful, 9 or even 10 mpg would not be impossible. If, like the rest of us ancient gearheads, you like to see the smoke - then you need to open your wallet a little wider, because your fuel bill will grow proportionally.

The 673 cid, 711 cid and early Maxidyne (237, 285 and 300 hp) engine blocks were all the same external dimensions just like the small block Chevrolets. When you add turbochargers, aftercoolers, hydraulic steering pumps etc. the space required for an installation does change.

If the early Lanova/Mack diesel was available in your truck with the transmission that you have, then the 673 or 711 should bolt in. That old transmission, however, was not designed for the tremendous torque of the Maxidyne engines, and might not be the best choice of gearboxes, if you go with the big power of a Maxidyne.

Some of the various engines might have the starter located in a different location from yours. There will be a bellhousing available to allow a corrected location, if your bellhousing won't work. And I don't know if it will or not.

As for the "mounts", at least in the B model Macks - the engine has a front mount on the forward most crossmember and the rear bolts to the transmission, which in turn, hangs from two mounts on the frame. I have never changed a gas engine to a diesel, so I don't know what you're dealing with for existing mounts.

As for my personal power combination - my situation just changed this morning. I have been able to buy a B61 single axle road tractor with a 673 and a triplex, and a 711 powered R600 long wheelbase single axle tractor with a duplex direct drive transmission. So my options have increased. I will probably finish the B67 more as a local use toy and do the B61 for longer drives because the cab has more room inside. What that means is that the B67 will get its original 673P (185 hp) with a .86 overgear triplex and its original 5.46 rear end on a new air suspension. This gives me only about a 60 mph top speed, but with real good pulling power.

Power management is fairly critical with the lower power diesels, and you need to decide whether you want to pull weight or go fast. You probably won't be able to both at the same time very well.

If you want to do what Fred is thinking of - that is retrofitting a 237 hp Maxidyne to his B61 - then you get more performance all the way along the scale. That is, you can pull more and go faster. And it is very dependable, as long as the driver is careful not to overstress the gearbox and the driveline.

Have you contacted the Mack Museum in Pa. ? And you might also want to log into www.oldmacksrus.com and surf around. Tom Gannaway and several real authorities have put together a tremendous resource of information on that site.

Have Fun, and remember (Tom Gannaway told me this) - there is no wrong or right - it's what works for you.

Paul Van Scott

[Packer]

There is a differance between electronic injectors and manual fuel, as in linkage and electronic throttle. That was where I was headed.

My mind is OK(?) - - - I just didn't say what I meant!!! Or thought I new for that matter!!

I's hell to get old!

Packer

[mackattack2]

hi,

I was mislead on the model number of the truck that I recently purchased. It's not a LJT like the paperwork states or the photo of the data plate the seller showed me, but its a smaller 125LS per the dataplate actually attached to the truck. Does that make any difference with your recommendations above?

Thanks.

Steve