67truckguy,
I figure the core is rebuildable because it ran good but had a lot of blow-by. That being said, I have two core motors, so if one was bad, we could try the other. I have no problem with a close inspection as long as everything get put back on. I could also take the core to a Cummins mechanic and have them inspect it (on your dime).
I am easy to work with!
Bill