Small Diesel Rebuild Hours

I said, that I have seen 1 UNIT fail, due to being improperly loaded ( combination of washed liners) and exhaust riser leaking into exhaust ports.

I agree that rebuilding the upper end such as the cylinder heads increases cylinder pressure too much and puts more wear and tear on already somewhat worn rings, rod bearings, and ultimately main bearings. I have been told by several master engine builders that it's best to leave the heads alone (unless there's a major problem with them like bad valve guides) and rebuild everything all at once later, and agree with this.

A full crack test???? Do you mean you have the large blocks "Magnafluxed"? It's a good thing to do as well as having the block align honed and the deck blocked and having everything balanced.

I've seen many engines go way past manufacturers recommendations, but in order for them to do so (in most cases), they're run a lot, almost 24/7. I knew one mechanic that worked for the New York water system and they ran 6v71 pumps submerged in water and got 50,000hrs out of some of them. They'd start them up out of the water, lower the entire engine underwater, and it would run a week straight before they'd pull it out to check oil and such, then send it back down. In today's day and age, I'd rather replace a generator rather then rebuild it. Technology has changed a little and by the time you do a major on the gen, and rebuild the generator end, you're close to the price of a new one, unless it's very hard to get the old one out and a new one in.