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Cat 931B cummins engine swap

magnagreg

New Member
Joined
Sep 11, 2019
Messages
1
Location
central virginia
Bought a Cat loader with a hole thru the block... did a little research on block/engine availability before hand. Price wise, it would be pointless to spend the amount the dozer is worth trying to replace with a OE cat 3204.. I HAVE purchased a 4BT and will need some machining on the bell housing, flywheel, and crank adapter to make it work with 3F/3R transmission. ANY Recommendations? any body know how the youtube guy "labrador iron" is to work with or how I might get in touch with him? He posted several videos on machine work involved .. he did have a video posted of tractor running afterwards but didnt go anyfurther on "follow up" year later videos..
 

Joe Fick

Well-Known Member
Joined
Jul 27, 2017
Messages
104
Location
65459
Wouldn't it be better if you bought an engine from a salvage yard. Cat and Cummins are 2 very different engines. Yes it can be done but the results may not be worth it. I'm guessing the 4bt Cummins is a smaller moter than the 3204
 

Fat Dan

Well-Known Member
Joined
Jan 14, 2020
Messages
175
Location
Alaska
I'm with Joe on this one even if they have equal hp. I put a ford engine in an International for a friend it worked but not like it did in my mind. The parts I had to manufacture was a daunting experience I wish never to encounter any time soon. :mad: The the gearing between the trans and ring n pinion were not very compatible. It seemed to me there were thousands of tiny little problems that would pop up and take many hours to cobble together. So if your time working the vehicle is worth it by all means slap er together but if your time is worth anything add that to the total price tag. I think you would come out ahead of the game, both in time and money, if you put in an engine that is comparable.
Either way good luck.
Fat Dan
 

Fat Dan

Well-Known Member
Joined
Jan 14, 2020
Messages
175
Location
Alaska
Bought a Cat loader with a hole thru the block... did a little research on block/engine availability before hand. Price wise, it would be pointless to spend the amount the dozer is worth trying to replace with a OE cat 3204.. I HAVE purchased a 4BT and will need some machining on the bell housing, flywheel, and crank adapter to make it work with 3F/3R transmission. ANY Recommendations? any body know how the youtube guy "labrador iron" is to work with or how I might get in touch with him? He posted several videos on machine work involved .. he did have a video posted of tractor running afterwards but didnt go anyfurther on "follow up" year later videos..

He may have realized his project was too daunting.
 

kshansen

Senior Member
Joined
Mar 11, 2012
Messages
11,129
Location
Central New York, USA
Occupation
Retired Mechanic in Stone Quarry
Thing I see with these kind of projects is that if you have the tooling and skills to do all the machining and fabricating yourself you might end up with a working machine at a reasonable cost.

But if you have to pay a machinist to make adapters and they also have to design the adapter the cost will spiral out of control in no time. Just modifying the coolant lines could cost a pretty penny. Also does the engine have coolers that can adequately handle the needs of the 931B? Is the 4BT engine oil system configured to handle the demads of this 931B, I mean the conditions a 931B may be used under might be very different than the 4BT was built to be used.

Basic things like is the flywheel housing of the Cummins designed for a "wet flywheel"? Are both engines running the same SAE size flywheel housings? Just looking at the displacement of the two 3204 5.2 liters and 4BT 3.9 liters has me wondering if the 4BT would have the torque output needed, could not find those spec's real easy online but still have to wonder.
 

DB2

Senior Member
Joined
Jan 4, 2015
Messages
1,008
Location
Winnipeg MB Canada
We had 4BT’s that had a hydraulic pump drive under the injection pump. The OEM ran a big Cessna style gear pump and a smaller back to back steering pump. I still have at least one. I’ll take a picture if anyone wants to see.
 
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