Rebuilt cm 870

[tree98]

(01-28-2023 )Izzyrod52 Wrote:  What can I expect from an overhauled cm 870? It's a 435 with a fresh overhaul and it was just broken in last weekend. Went for a test drive and it ran very well. I'm interested in buying the truck but I wanna get some opinions here first.

The number one question is who rebuilt it? There are certain procedures that must be followed to get the most life out of an ISX.

Only OEM internals, no aftermarket crap inside the engine.

Counterbores must be cut and liners shimmed up to .014

The old cylinder head must be replaced with a new OEM cylinder head, not a "reworked" or "rebuilt" head. You most certainly can't re-use the old head!

The head must be torqued down and then let sit overnight for the gasket to crush, then retorqued and the final 90 degree turn on the bolts

If these things aren't done, you don't have an engine that will last a million miles without major problems. You will likely only get maybe 200k-300k before a liner breaks loose or some other reason to tear it all back down again.

Also make sure it wasn't put back together with RTV on the gaskets, or instead of the gaskets!! That's the kiss of death for an engine. Here's a recent example of this https://rawze.com/forums/showthread.php?tid=8578

Last but definitely not least, is it demandated? If so it's likely a bad program and you'll need to have that straightened out immediately.