Jerry, I'm not sure what to say about the alternating overhauls. Right now, I'm at about 1750 SMOH, but 650 on new cylinders. On top of that, all the cylinders have been reconditioned since. In my case, it would be acceptable to just do the bottom and the engine would be identical to one with 650 SMOH. Then why not run it until it's time to do the top again? The bottom would still be fine. The difference would be in name only; it would still need to be referred to as 1750+ SMOH. And that is the problem. It would be more difficult to sell.
If everything else looks good, such as the screen/filter we talked about, compressions, and the oil pressure I might be inclined to think of it as 495 SMOH. Even if it legally isn't.
There is the chance that some shortcuts were taken, but that can happen with a major overhaul done in the field too. There just is no way to tell. If the owner has been doing oil analysis at oil changes, that might help.
Edit: Ooops! I think I made a mistake here! Was the top 4-500 hours before the bottom end overhaul which was 495 hours ago? If so, then it is more like an engine with 1,000 hours since major. Unless of course, the cylinders were removed, overhauled and put back on. If the cylinders haven't been replaced or overhauled in about 1,000 hours, then he really shouldn't be advertising as 495 SMOH. That is a bit of a red flag. And if the cyls have that much time on them, plan on needing a top end overhaul sooner than later!
Last edited by Eric_Salvo; 02/15/08 11:35 PM.
