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350 Cummins in a B 42? Is it a possibility?


Craig N

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So I’m picking up a nice B 42 in a week or so, with any luck. Body is great, but the motor (673 NA) is locked from sitting for about 4 years. The plan is to pull the injectors, put some marvel mystery oil in the cylinders and let it sit for a few days/week. I’ll Jack up the rear, put the duplex in high gear and hopefully rock the wheels back and forth to get her unstuck. I’m going to try doing this rather than try pulling it on the road.  
 

That said, if I can’t find another 673 somewhat local to me for a reasonable price, I have a Cummins 350 (which is also probably locked) that I have access to. It’s basically brand new. I could tare the heads off of it and try unlocking it and see what happens. 
 

So, will a Cummins 350 fit in a B42 chassis?  What are my twin stick transmission options for that motor?  I’m assuming I’ll need new motor/transmission mounts to start with. Great forum here. Thanks for all the help and information. 

0B0497FB-B96A-41B0-A159-7B464789C774.png

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7 hours ago, tjc transport said:

that is a big engine. 

a better fit would be a 6BT. they can easily make 350 hp with very little money. 

 

I do like the 6bt’s, I have one in a 2001 dodge. I would probably go with a Mack 237 or 285 before I did that though. Would like to bolt a twin box back up to it. 

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1 hour ago, 70mackMB said:

Welcome Craig,  Welcome to BMT and your off to a good start! Interesting post with a picture the first time. lol    .....Hippy

Glad to be here!!  Cool pic, right?  I should have better ones of it tomorrow. 

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19 hours ago, davehummell said:

Get a 675 it fits without too much hassle use your flywheel and front balancer and water pump I did it and it was a piece of cake.

Oh nice, that’s probably the way to go. I think the transmission will bolt right up too. From what I’ve read, the 675/237 has way more torque and can blow the transmission easy if you aren’t careful. I won’t be hauling anything with it anyway, just gonna be a cruiser. Hopefully I can get the 673 running anyway. 

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I like the bumper its diffent than a flat one truck looks to be in good shape I also have a b42 was the rear in yours changed to a diesel rear or are they still running a gas rear the ratios are way diffrent in them

If your going to be a bear be a grizzly

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1 minute ago, Mean Green said:

I like the bumper its diffent than a flat one truck looks to be in good shape I also have a b42 was the rear in yours changed to a diesel rear or are they still running a gas rear the ratios are way diffrent in them

That’s a good question, I have no idea. How would I tell?

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3 minutes ago, Craig N said:

That’s a good question, I have no idea. How would I tell?

Jack one rear wheel up and spin one revolution, count how many times the driveshaft spins and divide by two (such as 9 driveshaft revs would be a 4.50 diff ratio).

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is yours a single axle or tandum mine was a single axle with a regular rear there is a flat spot on the carrier that will have your gear ratio stamped it in mine had 6.17 gears they never swapped it out when they but the 673 in it I ended up putting a double reduction 4.61 I think out of a diesel but have since removed it to air ride it

If your going to be a bear be a grizzly

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17 minutes ago, h67st said:

Jack one rear wheel up and spin one revolution, count how many times the driveshaft spins and divide by two (such as 9 driveshaft revs would be a 4.50 diff ratio).

I’ve done that with old Fords before. What’s the gear ration for a gas job or the Thermodyne diesel?

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18 minutes ago, Mean Green said:

is yours a single axle or tandum mine was a single axle with a regular rear there is a flat spot on the carrier that will have your gear ratio stamped it in mine had 6.17 gears they never swapped it out when they but the 673 in it I ended up putting a double reduction 4.61 I think out of a diesel but have since removed it to air ride it

Single. I’ll have to check when I get it home next week. Paid for it today, just gotta line up a ramp truck for the weekend. Guy I know has a landall but not sure he’s got a winch. I’m gonna call a guy who’s got a ramp truck too to see if he’s available. 

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1 minute ago, Mean Green said:

if you need rear I have one that was out of my truck don't know where your from but it's just laying around

That’s awesome!  We’ll see what it’s got when I get. I appreciate the offer. I’m in Massachusetts, where are you located?

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I've got a 237 with a 5 speed mack trans bolted to it. Engine smokes a bit, doesn't like to start in the cold. Most everything else on the truck is gone, and we haven't had it running in a few years.  Was a U675T, I think 1974 or 1976. If your engine is no good then send me a PM, I can check with my dad to see if we want to sell it. 

Zip code 18914.

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