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chris88

A Few Questions On My B 61

18 posts in this topic

Hi, I just picked up my B this weekend and have a few questions. First lets start with that 12-24 volt series parallel switch thing. How exactly does it work. How are the batteries wired? Im guessing that each bank of batteries is seperate and wired for 12 volts then put together at the switch to make 24 but i dont know. I would like to put a 12 volt starter on and get rid of that whole contraption. What would i have to do? Just put a new starter on and run the battery cables to it right? Should be no big deal.

My other question is to do with tires. Its got 10x20 on it right now. Only 5 spoke rear hubs. Ive heard that 22.5 tubeless rims will fit on a 20 inch hub. Is this true? I'm sure I'll come up with more questions soon but thats all i can think of now.

Thanks

Chris

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Forget the tire question, I just read around a bit and found out that i can put a 22.5 tubeless on. Another question i have is about that oil bath air filter. I see watts mack has a replacement dry type but its a little pricey. Are there any cheaper alternitives or is that about it for a dry filter housing. I deffinatly want to get rid of the oil bath.

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On the S/P switch thing here is a quick bit of info.

You hook two 6 volt batteries togather to make 12 volts for lights, radio,(in a 'B' Mack? that's nuts! Can't here it anyway) and etc.

The S/P switch hooks the two 12 volt systems to 24 volts for the 24 volt starter.

You can pull the 24 volt starter out and replace it with a 12 VDC starter and get rid of the S/P switch.

Packer

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So all i need is one 12 volt on each side to make 24 for the starter. I just have to find out which cable is positive and which is negative. The truck should be positive ground right? Both cables are running towards the front of the truck by the cab so im not sure which is ground. How should i find the ground? Also I was wondering does anyone know an online tire site? I tryed searching on google but i couldnt find anything for truck tires, just cars.

Thanks

Chris

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Throw away the s/p switch. Install a 12v starter and 12v batteries and put an alternator on it. My 2cent.

10.00x20 takes a 7.50 rim and the 22.5 tubeless will take a 8.25 rim. The 7.50 might work, but if your heavy the sidewalls might rub each other.

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I did as Rick said

I nstalled 2 new 12V battiries and ran them to a 12V starter charging with a new altantor. My B only had one batt box so it worked out fine.

If I remember this was my cost from my mack dealer

the batts were $110 for both

the starter was $230

and the alternator was $120

To check if its positive ground just follow the + cabel off the batt and see if it goes to the frame rail

congrats and get us some pics

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There is a wiring diagram in the info section of oldmacksrus.com that covers the 12/24 volt series parallel system and its drawn out simple enough for even me to understand. While you are on the site, be sure to put your B in the registery.

Tom

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Thanks for all the help. Rick what do you mean about the 22.5 needs an 8.25 and the 20 needs a 7.50? I would have to buy new rims for 22.5s so the width of a 22.5 rim should be standard and have nothing to do with a 20 rim.

I tryed followin the cables but they all(4 cables, 2 from each side) run up under the cab. It will be a couple weeks before i see the truck again since its not at my house yet but next time I'll see if i can follow them all the way up. As soon as i get rolling on the project I'll go buy a 12 volt starter. There are pictures in my gallery, I'll get more next time i go see the truck.

I hate to bother you guys but i have another question on the truck. The trunnion is one cast piece on the truck and at the bottom its cracked on both sides, its been welded before but its still cracked in places. Is it safe to weld it? I would imagine it would be if it was welded right. The truck will never move a lot of weight so it should be fine.

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The crack can be welded and should cause no issue of done correctly. Im not shure how the rookie DOT cops would feel about it but it wont fall off unless its heavely rusted thru.

with no weight on it I cant see it as a issue. just keep your eyes on it after it gets welded

Trent

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what do you mean about the 22.5 needs an 8.25 and the 20 needs a 7.50? I would have to buy new rims for 22.5s so the width of a 22.5 rim should be standard and have nothing to do with a 20 rim.

11R22.5's are customarily mounted on 8.25 in wide rims, and these are a direct replacement for 10:00 x 20's.

I tryed followin the cables but they all(4 cables, 2 from each side) run up under the cab. It will be a couple weeks before i see the truck again since its not at my house yet but next time I'll see if i can follow them all the way up. As soon as i get rolling on the project I'll go buy a 12 volt starter. There are pictures in my gallery, I'll get more next time i go see the truck.

If your going to rewire it for a 12 volt starter right away, this is immaterial, just take all the cables out and start over.

I hate to bother you guys but i have another question on the truck. The trunnion is one cast piece on the truck and at the bottom its cracked on both sides, its been welded before but its still cracked in places. Is it safe to weld it?

Yes, it is safe to weld it, just be sure to vee out the cracks to insure good penetration of the weld.

Add reinforcement plates if necessary. 7018 rods or er70s mig wire works good for this. (I still have burn scars on my arms from welding on those)

Good luck with your new truck!

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If I recall, all the cables did go to S/P switch, cause you need to mix/match them to get 12/24v, so the positives did not just go to the frame.

Get the 12v starter, batteries and alt. Simple and much more effective starting system.

Get 11r22.5 tires and matching rims, any truck shop will have what you need in stock. Common tire/rim combo. Order the whole set up at one time and bolt them on. Used rim will cost you about $50ea.(sandblasted/painted).

Run the old oil bath. Unless someone can get you a dry type cheap. I still run mine with oil bath unit. Clean the pan, put a clean qt(something like that) of oil in it and drive it. Unless you put big motor in it, the old unit will work just fine.

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Run the old oil bath. Unless someone can get you a dry type cheap. I still run mine with oil bath unit. Clean the pan, put a clean qt(something like that) of oil in it and drive it. Unless you put big motor in it, the old unit will work just fine.

Hi Freightrain. Sorry to butt in on this thread, but as I'm replacing my old 673 with a "C" motor turbo-charged, are you suggesting the old oil bath should be replaced. The reason I ask is, I vaguely remember this being mentioned somewhere before. I would appreciate your comments.

Regards, Rod.

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Hey Rod.

From the information I've heard(and pretty much agree) is the lack of air flow thru the old oil bath units. With bigger power motors, you need more air into them, so getting the dry element unit is a definite upgrade. Did they still have oil bath with the C motor? I'm not up on what/when they quit oil bath.

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Now in the final stages of the conversion to the "C" motor.

Is there anything wrong with me putting a filter like this on the front of the turbo, instead of yards and yards of ducting and 180deg turns etc?

I would still keep the old oil bath on the outside.

Comments appreciated.

Regards, Rod.

post-52-1171691821.jpg

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:mack1: If that is what they call the 250 horse, which if believe was a 673 C engine, when they came out they all had oil bath air cleaners. terry

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Now in the final stages of the conversion to the "C" motor.

Is there anything wrong with me putting a filter like this on the front of the turbo, instead of yards and yards of ducting and 180deg turns etc?

I would still keep the old oil bath on the outside.

Comments appreciated.

Regards, Rod.

post-52-1171691821.jpg

Hi, Rod.

I looked at the photos you posted, and I see that your truck has the bottom inlet air cleaner.

I have never seen a factory turbo engine equipped B model with the bottom inlet air cleaner.

All the ones I've seen had the top inlet oil bath air cleaner.

I don't know how much difference there is in air flow from one to the other, but the bottom inlet type certainly has a smaller inlet, and is smaller in size over all.

If you could switch to the top inlet type, that would be the stock setup.

As was mentioned previously, that filter under the hood will draw hot air, reducing your power.

Herb.

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:mack1: Re air filter. Hotrod the filter in the pic would be usless as it would get clogged up fast with the fumes circulating round the engine bay. As for the hot air, a turbo is only a compressor anyway. the average air temp out of a turbo is around 250 degrees or there abouts. Even with a intercooler you only get the air temp down to 180 degrees or there abouts. The C motor had a oil bath air cleaner anyway. Mark

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