Run overhead or not?

Turbo at 500k is about at the end of its service life. So i can't fault him there. Especially if his history shows 500-600k he's replacing turbos. There are indicators to turbo failure though that should give yoi adequate warning though.

Overhead wouldn't be a bad idea. This engine closes the valve clearance as it wears. So the gap goes away. I'd be leaning towards doing it.

 

Just pop the rocker cover off and inspect the cam and followers,just check the lash on all valves and see if there in spec if they are leave them alone if not adjust them.

 

Detroit intake valves tend to tighten up. We do VA's initally at 75,000, then 300,000 after that. At 300,000, most of the intake valves are down to 0.002-0.003" lash. Run them too tight and you chance burning a valve. Most of our VA's end up being just a check on the the injectors and exhaust valves, we rarely have to adjust those, but the intakes are always too tight. The initial one at 75,000 is by far the worse, it all over the place (some tight some loose). Once we set the initial, things settle in and lash stays fairly consistenst (all wear about the same).

My opinion is to run through the overhead, don't touch anything that is in spec, adjust what is out. Check the rocker rollers closely too. Ceramic rollers are very tough, but once they start pitting, they go out fast and take the cam with it.

 

Yes, Detroit valves do like to tighten up. I would run the overhead. 200K is too soon, but you are about right on now. Turbo should just be inspected for radial and axial play. I think 500K is too soon for a PM replacement.