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jdstl

Where can I find engine info on a 673 Thermodyne (1959 B61)

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Hey everyone,

new to the forum and vintage Mack trucks. I just bought a '59 B61 with the 673 diesel. I have been searching this forum and the internet in general but haven't come up with much good info on the engine. I don't have any paperwork or manuals with the truck. It runs but I would like to start out with changing all the fluids/tune up type maintenance. What weight oil is recomended for these engines? Capacity? What about oil type and capacity for the transmissions? Its a 5+2. I was also hoping to find some info on the injection system but have come up dry on that as well. I think the injection pump could use some adjusting, it seams like its very underfueled... No smoke at all and the truck is pretty gutless. Most of the videos I have seen, they do push some smoke. I think with a little more fueling it would be a little nicer to drive. I didn't just want to go start turning screws on the pump though. Also any recomendation on a place to purchase a repair manual?

Thanks for the help,

Jason

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Pictures?

First thing to do is to write the Mack Museum with the chassis number and ask for a history of the truck. They should send you an owner's manual.

Send along a suitable donation for the service. It's not required, but most folks here consider it the civil thing to do.

You should get lots of help from the B owners on this site. Good luck with the new rig and have fun putting it back the way you want it.

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Thanks for the response. I tried contacting the museum but they are closed untill next week. I'm hoping they can set me up with some good info, I have heard they are great to deal with. I haven't got any pictures yet, but I'll get some up. Its a single axle with the concave cab.

One other question to add, what is involved to change the wheels to a newer 22.5" setup? Tires would be much easier to find and less expensive.

Jason

Edited by jdstl

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Most of us run Rotella 15w40 in our trucks. About 6-7 gals takes care of it.

If you still have 20" tube tires, you can buy a set of 22.5" tubeless rims/tires and bolt them on. That was the first thing I did to my truck when I got it.

I've played with my pump, had it running pretty good. The bad thing was when fuel prices went up, I turned it back down to get decent mileage out of it. I average 8-9 mpg pulling my trailer. When it was turned up...about 4 mpg!!! She sure did put out the smoke back then.

Which pump? There are a couple variations.

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I still run SAE #30 weight Rotella only because the old book called for that oil. The owner before me just held up a jug of Mobil 15w40 and said he uses that in all his trucks. As for the wheel and tire combo. I'd do just like Larry said. I also have the 22.5's on the steers and have the tube tires on the drivers, (original setup).

Regards

mike

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Thanks for the info... I'm sure the owners manual will have the info but alot of times stuff from the 40s and 50s is outdated and specifies weights of oil that aren't even available anymore. I didn't just want to go dump 15-40 in and assume its ok since most diesels take it, I know Detroits need to have straight weight oil for example, so I just wanted to be sure. I've never worked on a diesel this old. I'll have to go look and get some numbers off the pump. Definently gonna start looking for some 22.5" dayton wheels.

Jason

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Jason,

As someone said earlier - start with the chassis number and get it to the Museum for individual truck info.

Just FYI - keep your eye on E-Bay (Motors - Vintage Parts). Quite often there are service and/or maintenance manuals up for auction. Just beware that you are buying a usable book for your truck.

I have also had some success by contacting retired mechanics, or shop owners in my area and asking if they had any of the old books that they might sell.

Happy New Year - and Best of Luck with your new truck!

Paul Van Scott

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Jason,

As someone said earlier - start with the chassis number and get it to the Museum for individual truck info.

Just FYI - keep your eye on E-Bay (Motors - Vintage Parts). Quite often there are service and/or maintenance manuals up for auction. Just beware that you are buying a usable book for your truck.

I have also had some success by contacting retired mechanics, or shop owners in my area and asking if they had any of the old books that they might sell.

Happy New Year - and Best of Luck with your new truck!

Paul Van Scott

Hey Paul, it sure is good to see you back around here.

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if you need any help my grandfather was a mechanic for Mack and i have the factory manual for he motor the original owners manual and the factory maintenance manual for the 673 and the b-61 if you need any help or info just let me know

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Thanks for the link and thanks for the offer dieselerock! If the Mack Museum can supply me with the service manuals along with the owners manual I would rather get it from them and send a donation. If not that is exactly what I'm looking for, and $40 sounds more than reasonable for 200+ page manual.

Jason

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Freightrain:

Looked at the pump its a Bosch though I couldn't make out the numbers.. is there more than one bosch pump or do you know what to adjust to get more

fueling?

Thanks,

Jason

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Freightrain:

Looked at the pump its a Bosch though I couldn't make out the numbers.. is there more than one bosch pump or do you know what to adjust to get more

fueling?

Thanks,

Jason

Most 673 engines used a pump with 9mm barrels. If it is a natural aspirated engine I would prolly leave the pump calibration alone as parts are getting scarce and expensive. If you choose to rebuild then engine and incorporate some modifications it will stand a lot more fuel and resulting power but it still doens't have piston coolers and the engine will be short lived if worked reasonable. Not saying it cannot be done but those engines were not near as strong in design as something of the later "Maxidyne" engines althought they look the same externally. If you are not getting any smoke at all and are really down on power, start with fuel filter changes and rack travel adjustment. This is about all you can do without a lot of work that can be expensive to have done.

Rob

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Mack museum is the way to go. I called with my chassis number and they sent everything they had on the truck. Service manuals, original build sheet, operators manuals, etc. Don, the curator, is a great guy. For parts call Kevin All. He rebuilt my little en 291 in my B20. He has every part you would ever need. eBay is a great source as well. Watts Mack, king of salvage.

Good luck with everything. Keep us posted!

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Ya not looking to melt it down... I changed the filter and it made no difference. I'm not looking to max it out I know how egts skyrocket with lots of fuel and no extra air from a turbo to clean up the fuel and keep things cool. Also should mention I won't be towing anything heavy with it and probably most of the time I will just be bobtailing it anyway.

Thanks

Jason

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Contacted the museum yesterday hopefully should get a nice packet in the next week or two.

Jason

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Hey everyone,

new to the forum and vintage Mack trucks. I just bought a '59 B61 with the 673 diesel. I have been searching this forum and the internet in general but haven't come up with much good info on the engine. I don't have any paperwork or manuals with the truck. It runs but I would like to start out with changing all the fluids/tune up type maintenance. What weight oil is recomended for these engines? Capacity? What about oil type and capacity for the transmissions? Its a 5+2. I was also hoping to find some info on the injection system but have come up dry on that as well. I think the injection pump could use some adjusting, it seams like its very underfueled... No smoke at all and the truck is pretty gutless. Most of the videos I have seen, they do push some smoke. I think with a little more fueling it would be a little nicer to drive. I didn't just want to go start turning screws on the pump though. Also any recomendation on a place to purchase a repair manual?

Thanks for the help,

Jason

Also try the wiki pages on this site, they have a lot of really good info.

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