Truck Repair: 3406 b break in, nuts and bolts, moderate load

Question
Jeff: I have a disagreement with our company mechanic.  He's rebuilding a 3406 b model engine.  His way of breaking in fresh engines is to idle it for 10 minutes and then putting the throttle at 1500 - 1800 rpm for 30 minutes and then turning it loose with a driver.  I disagree.  I say warm it up good, then go drive the thing, varying rpm under moderate load, for a few hundred miles before letting it loose with a driver.  The engine will be in an end dump pulling pup trailor, 56,000 truck, 101,000 in combination.  How would you break this engine in?

Answer
I would take it out on the road and run it for 60 miles or so with a empty trailer to let it get to operating temps. then would bring it back and check for leaks check all your fluid levels. then my next choice doesn't always work that way is to give it to a driver that I know isn't going to rag it out and let him run close to home with it for a few days to make sure no problems don't crop up. after a few days i'll let it go. If you put all new parts and turbo on it I think that's a safe choice if you reused the turbo and just cleaned the pistons and put on new rings and cleaned the liners I would not load it over 80k for a month. As for who is right I would probably go with your answer based on the weights your hauling. his isn't a bad answer I letting it sit there with the idle bumped up doesn't allow nuts and bolts to come loose from the bouncing around on the road so a test drive is absolutely called for. Then I like to bring them back in after 50k and run the rack on them to make sure all your lash adjustments are still in spec.