Rebuilt cm 870

[Peashooter67]

After everything I went through with mine these are my words of wisdom.

First is listen to what Rawze posted in response to your question.
Second. If you were not there to oversee the “rebuild” you don’t know nothing but what “they” tell you.

Here is my take with my experience to properly rebuild an ISX CM870

New head

New harmonic balancer

Rebuild your rockers because it’s easy and will save your cam but this part is not necessary

If your crank shaft is for any reason been turned to an under size GET a NEW CRANK SHAFT that is standard size

Use cumins internals “ bearings,rods,pistons,gaskets, head gasket”

Deck your block and cut your counter boars then shim your liners 15thou protrusion

Use new head bolts and rod bolts.

Put a new clutch in while you’re doing this.

Use a new oil pump and shim the regulator in the pump while you’re at it.

Be sure you have a good operating program in your ecm.

Rawse, did I miss anything?



I bought a truck because it had a fresh rebuilt motor a few years ago. As a result this motor cost me more than the truck did and just about put me out of business and I had two trucks on the road when I bought this truck.

When I first bought it it ran fine and shortly later had a serious oil pressure issue that needed up costing about 18k to find and fix the problem then 108000 thousand miles later the crank broke and I had to rebuild the motor front to back top to bottom for about another 28k or more.


If it were me I’d rather buy one that need the motor rebuilt so I can do the rebuild or be a big part of the process.
As far as this truck you asking about you pay your money and roll the diece. Oooodddsss are you will lose.

Grab your wallet and run away from this truck as fast as you can. That’s my advice knowing nothing more about the truck.


Who rebuilt the motor ?
What did they do and what is left on the list they didn’t do?

I can nearly bet and be 100% right that the harmonic balancer has never been replaced so soon you will have a broke crank shaft if it has not been replaced. That’s the end result of a bad harmonic balancer.

Your ifsm will most likely need a thorough cleaning and some repair also. If the egr system is in tact and functioning it will also need a lot of cleaning and maintenance to bring it back to proper functioning operation.