Rawze.com: Rawze's ISX Technical Discussion and more

(12-30-2018 )Peashooter67 Wrote: [ -> ]Wrong rod and main bearings were used in the original rebuild

Oh man... Another victim, that sucks.

A few thousand miles into my first week with the Pete and my troublesome 870/871
iSX.

I’m happy to report although I think the gearbox “see air compressor “ is a bit noisy, I can’t realy say it’s worse than my 570/571 ISX?

Back to my purpose of this “probably last post to this thread” I’m glad to report that the motor runs smooth at 65-70mph loaded and empty with good power.
My best guess till I get a chance to hook up a laptop to the ecm is its set at 1850 torque.
Fuel mileage seem really good especially for a 379 Peterbuilt.

Now to the meat and bones.

I’m about to pull out of Baytown headed back to the DFW area and even at 200* on the water and 210 to 215* on the oil “these have been max temps according to the gauges on the dash” my oil pressure has yet to drop below 40 psi on the highway period ! above 1300 rpm.

This is great news after putting about 17k into a supposedly rebuilt motor from a certified dealer/repair center for the Cummins engine. My oil pressure woes seem to be cured.

I will occasionally post a comment to this thread with updates as to how my Oil pressure is holding up.


If you have looked at and think you have covered every reasonable cause to low oil pressure and can’t find a reason plastigauge your main and rod bearings even if they LOOK OK.

New update




71,300 miles and oil pressure still. Doing. Fine.

On a fresh oil change and hot Texas summer heat at 1,500 rpm the oil pressure now depending on oil temp and coolant temp the oil pressure hovers around 40 to 42 psi.

Now to work on correcting other small issues.
Fuel pump to injectors and look at ecm programming to make sure it is right and calibrated properly.

WELLLLLL!!!!!!!!!!!!


A little over 101,xxx miles on rebuild and my engine is trashed.

Front crank bushing / bearing went out. I don’t have the motor open yet but I’m 99% certain there is little metal flakes run all through the motor.

Can’t wait to open it up and figure out what happened.



Sssoooooooooooooooo........... here is the million dollar question?????????


I’m buying a used running low mileage motor and pulling this one out for core.
What is in the truck is a cummins isx cm870 .....

What should I put back in its place?

Do you have the ability to go from an 870 to an 8-71 which requires a few wiring changes but everything else the same there's a few members I can give you more information basically you're just upgrading to have an electronic turbo and easier ECM to program

This is kinda what my question is hinting at.


I have the laptop, internet, and team viewer.

The shop that has actually done a very good job working with me will let me use the laptop and I was thinking weather to get an 871??????

Keep in mind my truck is an 06 379 so no def,pdf,ect.....

What wiring changes do I have to do ?

I think this might be where I get Rawze / unileavers and my shop person on the phone ang get this thing organized.

its not a crazy swap. wiring honestly on the truck side is very close just gotta modify a few things, add some 1939, change the TPS depending on what kind it is. Its not that crazy.

Now converting a 870 into a 871 is much harder. dropping a crate 871 in is ezmode.