Big Cam 400 Into A B-75

[fordguyhey]

hey everyone. I have the opportunity to buy a 400 Cummins for a good price and was thinking about putting it in my B75. Does anyone know if I would need to get motor mounts out of a B73 with a cummins in it in order to make this work. Is there anything else that would make this a problem?

-Ryan

[vanscottbuilders]

You will need at least the front mount from a B-73. The transmission mounts are the same. I think.

The 855 Cummins is physically larger than the older 74-? cubic inch Cummins used in the B-73. I've been told that it is an easy swap - but we need you as a Guinea Pig.

Let me know how this works - as I also have a B-73 and a low mileage 400 Cummins looking at each other lovingly in the shop.

Paul Van Scott

[vanscottbuilders]

As a follow-up - talk to Kevin All at All Macks.

Not only does he know everything, but he actually built one of these B-73's with an 855 Cummins a few years back.

Paul VS

[Guest 45LMSWM]

Phil Wheeler up in New England used to own a restored B75 L-cab that I am pretty sure had a 400 Big Cam under the hood. I believe the truck was sold at some point, but can't remember who wound up with it. Truck was Blue with red frame and full fenders over the rears.

[fordguyhey]

As a follow-up - talk to Kevin All at All Macks.

Not only does he know everything, but he actually built one of these B-73's with an 855 Cummins a few years back.

Paul VS

Did all B-73s have Cummins motors or just some of them? I was under the understanding that the only major difference between a B-75 and a B-73 was the engine. I will call Kevin and pick his brain about it too.

[terry]

B75 is a non turbo mack engine a B753 is a turbo mack engine, a B73 is a non turbo cummins, a B733 is a turbo cummins, anda B773 is a turbo cummins. Gets pretty confusing! Terry

[theakerstwo]

I see two problems. The front mount on a B73 was a trunion mount meaning it was a rap around the center trunion that some old cummins had around the crank on the front cover. I have seen these mounts up later on 855 engines but have never seen one on a big cam. The best thing is use the front mount from a big cam and build your cross member that it sets on. The other thing is the flywheel and clutch will be a pull type if using the old mack trans.The flywheel from a 220 will not be same as a 855 engine.

[fordguyhey]

I see two problems. The front mount on a B73 was a trunion mount meaning it was a rap around the center trunion that some old cummins had around the crank on the front cover. I have seen these mounts up later on 855 engines but have never seen one on a big cam. The best thing is use the front mount from a big cam and build your cross member that it sets on. The other thing is the flywheel and clutch will be a pull type if using the old mack trans.The flywheel from a 220 will not be same as a 855 engine.

I see what you're saying about the mount. I guess I'll just fabricate off of whatever is on the big cam. As far as the pull clutch goes I've already got a swinging pedal and cable assembly out of an R model installed in my cab so I'll just need some bracketry underneath to support the cable and I should be all set.

[Truck Shop]

On 10/21/2010 at 6:10 PM, theakerstwo said:

I see two problems. The front mount on a B73 was a trunion mount meaning it was a rap around the center trunion that some old cummins had around the crank on the front cover. I have seen these mounts up later on 855 engines but have never seen one on a big cam. The best thing is use the front mount from a big cam and build your cross member that it sets on. The other thing is the flywheel and clutch will be a pull type if using the old mack trans.The flywheel from a 220 will not be same as a 855 engine.

Yes Cummins did make big cams with a front trunion mount. I have a 400 BC II CPL 449 setting in a Freightliner frame that has the front trunion mount. I know this is a old thread but-Cummins did make them.

 

Truck Shop

[12V71]

On ‎10‎/‎21‎/‎2010 at 6:10 PM, theakerstwo said:

I see two problems. The front mount on a B73 was a trunion mount meaning it was a rap around the center trunion that some old cummins had around the crank on the front cover. I have seen these mounts up later on 855 engines but have never seen one on a big cam. The best thing is use the front mount from a big cam and build your cross member that it sets on. The other thing is the flywheel and clutch will be a pull type if using the old mack trans.The flywheel from a 220 will not be same as a 855 engine.

Old thread... But the 220 flywheel for the CL-50 clutch will work on an 855, I have used it to replace V-8 Cummins engines with the 855 in M-123 Military trucks for farm use. The Cummins part number was 21010. I also had a jig I made to build trunnion crossmembers for the front mount. Oh, you had to drill the clutch housing bolt holes to clearance 7/16" bolts too. They were 3/8" on the 765 V-8. 

Edited August 25, 2018 by 12V71