CM 870 Overhaul Advise

[2dlb]

Hi Gents. I am in the process of rebuilding a 870.CPL 8519 was set at 475. Got a short block from Cummins, checked the protrusion as advised here and yup all over the map. Recut counterbores and all are at .014". Still waiting for a new head. If i'm not mistaken this is mid family and i know it was posted what the max this configuration could be set to but i cant find it. I was considering d blocking the egr. I know when we first got this in 2004 the thought was to unplug the egr and it would through the CEL and have no effect. i do remember reading about a ghost derate as well this thing ate a lot of turbos over the years from Cummins and from others, does the VGT require egt air to keep temps down? I was told in the 870 the egr only opened on deacceleration?? Any advice on cams and injectors would be appreciated
Thanks

[Rawze]

(10-12-2023 )2dlb Wrote:  Hi Gents. I am in the process of rebuilding a 870.CPL 8519 was set at 475. Got a short block from Cummins, checked the protrusion as advised here and yup all over the map. Recut counterbores and all are at .014". Still waiting for a new head. If i'm not mistaken this is mid family and i know it was posted what the max this configuration could be set to but i cant find it. I was considering d blocking the egr. I know when we first got this in 2004 the thought was to unplug the egr and it would through the CEL and have no effect. i do remember reading about a ghost derate as well this thing ate a lot of turbos over the years from Cummins and from others, does the VGT require egt air to keep temps down? I was told in the 870 the egr only opened on deacceleration?? Any advice on cams and injectors would be appreciated
Thanks

For CM870 advice in particular, get with forum member 'running rough'. He has owned and rebuilt many of them over the years and is also familiar with programming, etc. on them specifically.

[Peashooter67]

From my personal expensive experience

Just for the basic overhaul “internals”

All Parts must “with very FEW exceptions “ be Cummins parts. Unless you want to be doing this again in short order.

1st verification of Cpl and proper ecm program that matches Cpl.. this assumes factory stock virgin motor.

1- disassembly and inspection of parts as you take the motor apart. I will also try to take it account the age of the motor/vehicle. This is a good time to buy new sensors and wire harness.
2- purchase new head
3- if crank is to be reused it must retain original size journals , if the crank needs to be turned under standard then in the long rumen you are better off replacing crank with a new one or used that is still standard size.

Warning!!!! If you turn your crank .010 under or your original crank is already .010 under standard and you use it you risk having a broken crank soon after.
4- when you buy your cylinder kit get to broke rod cap “forget proper name” they don’t squirm under hard use.
5- get new harmonic balancer , if you don’t you are looking at a possible broke crank latter on.
Get new clutch while you are at it.

In short everything except the block needs to be replaced with new.
Head
Crank
Gasket set
Cyclder pack with fractured rod caps.
Harmonic balancer
New sensors
New wire harness
Cut the deck and have your counter bores cut. When you install your new cyclinders shim them .015” protrusion.
Get new rockers and rocker shafts too. At the very least rebuild your rockers to avoid trashing your cam and new motor.

I think in general this pretty much covers it. If you get a used crank under standard you risk a broken crank.
If you get a reman head it WILL crack.

Don’t forget new thermastats for your coolant and your oil cooler while you have the motor open.

[Rawze]

adding to this:
http://rawze.com/forums/showthread.php?t...2#pid78212

[Peashooter67]

Also get new oil pump and shim the oil pressure regulator with 3/4” of shims.
I superglued washers the size of dimes for my shims.

Your cams and rockers will tank you later. So will your rod bearing.

To do a proper rebuild on a cm870 is not cheap.
Don’t cut corners!
Also rebuild your fuel management system and do an injector leak test with your rebuild.
At the very least take your ifsm apart and clean everything well.