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Cummins big cam?


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Any big cam 4 experts here? I have a bc4 stc engine. For about a year now the jake on the front head didnt work. So today i decide to look into it. Got barely enough oil for the rockers and certainly not enough for the jakes. Only thing i can think of is spun cam bearing but cant think it would run a year like that. Only other thing maybe the injectors on number 1 and 2 are leaking to much oil and not enough left to supply the jake. Any ideas?

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If the injectors was fed oil from the cam brg then that could be the problem but the injectors are getting their oil from a line that goes in the top of the rocker box. and if that was losing that much pressure them at idle the stc would not be advancing the timing because it depends on that supply from the out side line.Could be a bad cam brg but if its spun the brg most of the time the paint will be burnt on the outside of the block next to the cam brg.I am no expert but did put in 39 years working trucks.

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glenn akers

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2 hours ago, fjh said:

These had a an issue with the piston coolers breaking off as well !They are plastic! Another easy place to look !


Just sayin!

I have had that people before on big cams an n14s but when that happened i dropped oil pressure.  This engine still has good oil pressure but i will definitely pull the coolers and check. Thanks

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  • 4 months later...
On Tue Jun 29 2021 at 8:47 PM, 14cxu613 said:

I’m trying to think what I did to fix my big cam iv when it happened. Did you check the springs In the jake housing?

I took the whole jake housing off. Started it up and barely any oil comes out the jake oil feed hole on top of rocker box

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On Sat Jul 03 2021 at 8:16 AM, theakerstwo said:

You should be getting alot of oil out of the rocker box with jakes off.It should spray about 6 feet up so look down on the block and see if the paint is discolored at that cam brg.It may have a cam brg bad.


Yes thats what i was thinking but the paint is not discolored.  

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