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6BT swap questions

Mrgior31513

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Finally back on my 5 ton project. Between buying some off-grid Az property and having a kid it's been sitting for a few years. Have my 6BT almost built, was wondering if anyone has any experience in swapping that with matching one up to the Spicer 6453 or close. I know it's the STD #2 bellhousing, but I'm still trying to sort out the flywheel. Sure it won't be too bad to source parts, as they used the 6BT in tons of industrial applications.

The engine flywheel for STD #2 comes in several variations for the starter location, don't think it much matters for my application, and I still have to figure out the flywheel and matching starter. Any input would be welcome.
 
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Jbulach

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I’m sure it’s been done, but cant think of anyone one here thats has. I know it’s been discussed and debated quite a bit, about how a 5ton is too much truck for a B motor.
 
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Mrgior31513

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I’m sure it’s been done, but cant think of anyone one here thats has. I know it’s been discussed and debated quite a bit, about how a 5ton is too much truck for a B motor.
A stock 6BT has about 215hp at 2,500rmp and 420 torque at 1,600.
You can push those motors to about 800-1k hp before you start to lose reliability.

It has forged pistons, I've put the Hamilton 168/208 cam in it for slightly increased hp and because it increases the spooling of the turbo at lower rpm's.
I am starting with 5x.012 injectors and I'm going to put a moderate turbo in it. Conservatively I'll be pushing about 340-380hp, and I can swap out injectors and bump it up to 5-550hp without blinking.

Seeing as how it's not a hot rod, and I'm trying to keep from pushing more power to the drive train than necessary, I'm starting small.

Considering they put the multi-fuel engines in these same trucks, I have no doubts that this motor will at the very least compare to the Mack, and most likely out perform it.

1950's Diesels are nothing compared to modern ones.
 

Mrgior31513

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I swapped in a 6BT with an AT545 as a married pair into my bobbed deuce. Never separated them.
I would have preferred a transmission swap at the same time, but mine has a PTO w/ winch in the front, and it's a pretty large price jump for the project to do that as well.
Is that a stock 6BT? How does it compare to the multifuel in pushing that truck around?
 

Jbulach

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A stock 6BT has about 215hp at 2,500rmp and 420 torque at 1,600.
You can push those motors to about 800-1k hp before you start to lose reliability.

It has forged pistons, I've put the Hamilton 168/208 cam in it for slightly increased hp and because it increases the spooling of the turbo at lower rpm's.
I am starting with 5x.012 injectors and I'm going to put a moderate turbo in it. Conservatively I'll be pushing about 340-380hp, and I can swap out injectors and bump it up to 5-550hp without blinking.

Seeing as how it's not a hot rod, and I'm trying to keep from pushing more power to the drive train than necessary, I'm starting small.

Considering they put the multi-fuel engines in these same trucks, I have no doubts that this motor will at the very least compare to the Mack, and most likely out perform it.

1950's Diesels are nothing compared to modern ones.
Yep, and thats how the one side of the debate, that I normally don’t participate in, always goes. You need to focus on the torque numbers of the two engines. Especially if you add 5-10 ton payload on your truck with a 10 ton tare. All the sudden your hoped up but dependable 5.9 isn’t going to be as happy. IIRC @hanksduece is bobed, so you’ll be comparing grapes to grapefruits. Just for reference, my 5 ton has a C motor in it that is just barely adequate. In all fairness it is stock, and I know your B can be built to run circles around it… Good luck, and hope you prove me wrong.
 

Mrgior31513

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Yep, and thats how the one side of the debate, that I normally don’t participate in, always goes. You need to focus on the torque numbers of the two engines. Especially if you add 5-10 ton payload on your truck with a 10 ton tare. All the sudden your hoped up but dependable 5.9 isn’t going to be as happy. IIRC @hanksduece is bobed, so you’ll be comparing grapes to grapefruits. Just for reference, my 5 ton has a C motor in it that is just barely adequate. In all fairness it is stock, and I know your B can be built to run circles around it… Good luck, and hope you prove me wrong.
I've done my homework, for sure. Comparing the estimated/potential hp and torque output of this modified engine should have it well above the Mack, and better than the multifuel at bare stock. I've specifically built it for lower end power, so the 1400rpm stock torque band compared to the 1200rpm band of Macks/Continentals coupled with the increased power should have it optimally tuned for this application. Also, not built for a towing/work rig. It's an RV conversion/toy. May tow a trailer with it eventually, or a car, but it shouldn't be a problem. If I was going for a workhorse I would have started with the newer 5 tons. I just wound up with this because it was cheaper than the duece and a halfs in the area at the time lol.
 

HanksDeuce

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Is that a stock 6BT? How does it compare to the multifuel in pushing that truck around?
My 6BT is completely stock from a fueling standpoint. The extra 170 lb-ft of torque with the 6BT is very noticeable compared to the multifuel.

Below is a link to a comparison chart of my original M35A2 vs after bobbing it (including engine comparisons).
https://hanksdeuce.com/M35A2_comparison.htm
 

Mrgior31513

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Sounds like a fun project jeepsinker also swapped a 6bt and has well documented it on here and YouTube.
It would have been easier to find parts for that swap, but I think I have it sorted. The Spicer 3053A from the M35A2 is a SAE #3 bellhousing, the Spicer 6453 from the M54A1 is SAE #2 bellhousing, so it's a different hunt for parts, same book but different page.

I think I have all the parts sorted save the pilot bearing, but I will need to pull the motor out for those specs. May spend some more time looking them up, but that sealed bearing the easiest, I can check a standard bearing for basic dimensions on that motor and spec out the center to match the input shaft. The flywheel, clutch and matching starter are the biggest concern and not very much reliable information on parts numbers. I found one conversion chart on the way back machine, but its not right on some of the parts (like giving one bellhousing number that is SAE #3 instead of #2) so I'm going to have to hope the starters listed on it match up with the other bellhousings that are right. @Big Mike's Motor Pool was nice enough to look up and send me the specs for the bolt spacing on the clutch, so I'm going to check that against the flywheel I have ordered, but I'm fairly confident it's going to match. When I get finished and have it running, I'm going to put the parts list up on this site and a few others.
 
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