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Discussion Starter · #1 ·
This discussion started under another topic but deserves it's own thread due to it's importance:

Hmmmm, Has anybody else done this swap and has any info to add. This is a new one to me. :idea:
Hi toolmanoffroad,
The pumps will interchange. You can even use one of the aftermarket super high volume 6bt pumps, but you don't really need it on a 4bt. But, If you are using a compound turbo setup, it would help. Those turbos take a large volume of oil!
Wrong 6bt has a wider gerotor. Pumps are NOT interchangeable
reedheadbronco

The larger gearotor is one of the reasons the 6cyl oil pump will pump more volume. The second reason is that the driven gear on the gearotor is smaller on the 6 cly pump, so the pump has a taller gear ratio, and spins faster. The gearotor is internal, and the external dimension of the pumps are identical. Also, the 4 cyl and 6 cyl blocks are machined identically in the oil pump area. The 6cyl pump is a cheap and worthwile upgrade. I agree, you shouldn't install a 4 cyl pump in a 6 cyl. I know the Cummins manual says they are not interchangable, and that is probably so you won't install a 4 cyl pump in the 6. My 4bt has a 6 cyl pump and it works just fine!
:D
Bob B.
 

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Discussion Starter · #2 ·
I was under the impression that the reasoning the pump interchange was due to the oil cooler size being different between the 4BT and 6BT? Maybe the pumps are engineered to work with their respective size cooler? So would using a 6BT pump along with a 6BT oil cooler in a 4BT be the properly balanced setup?

Also note that there was some discussion in "Diesel Power Magazine" recently on using the 6BT pump in a 4BT.
 

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When Cummins said parts were NOT interchangeable I assumed it would not physically fit depthwise into a 4bt. Now I'm curious.
 

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Info in Diesel Power Mag

Hey Bob S.,
Do you know what issue of Diesel Power had the bit about using a 6bt pump in a 4bt? I thought that the 6 cyl and the 4cyl had the same coolers. At least the 4bta's and the 6bt's. All I know is that it works. Also, some of the bigger turbos such as the HX35's and the HY35's and the HE351's will flow more oil. That's why I'm running a 6cyl pump in mine.
Bob B:beer:
 

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Discussion Starter · #5 · (Edited)
"Inside the Cummins 6BT5.9" September 2007 page 158 under "Oiling System"
"3 & 4 cyl engines used identical pump....capacity 15 GPM. 6 cyl had longer gears...rated 20 GPM...both ratings at 3600 pump RPM.

There is another article on a 4BT running a 6BT pump where it stated they used a 6 cyl pump for increased oiling but I haven't found that one yet.

Oil cooler differences was discussed in this previous thread:
http://4btswaps.com/forum/showthread.php?t=958
 

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What year pumps are interchangeable? Does it matter 12V or 25V?
 

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"Inside the Cummins 6BT5.9" September 2007 page 158 under "Oiling System"
"3 & 4 cyl engines used identical pump....capacity 15 GPM. 6 cyl had longer gears...rated 20 GPM...both ratings at 3600 pump RPM.

Here's the link for anyone that wants to learn more about the B series of powerplants.
 
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