671 turbo issue?

It may be obvious when you access the intake turbine with the air filter and hoses removed. The visible turbine should have no scratches or marks on it. Then, using nothing more robust than your finger, there should be no detectable side-to-side motion of the turbine, and only the slightest (if any) in-and-out play. The turbine should spin easily.

The turbine shaft floats in a layer of oil in the bearings. It might be that the exhaust side oil seal is gone, allowing oil to be pumped into the exhaust to burn, possibly explaining the gray smoke. but don't quote me on any of it, since I've never seen a turbo on a 671. If it were going into the intake side, there should be black smoke, as Ralph suggested in the overheating thread.

I worried he dropped a valve and punched a piston.

DO NOT run that engine until you get professional on site guidance. I once dumped a little more than that in about a half hour. Kissed that engine good bye.
It's $30K by the time the smoke clears to rebuild.

Those are the later 4 valve heads. You will need a proper shop to look the whole head over carefully.

When the head comes up, you will probably find burnt valve seats and edges of the valves missing also.

For my notes, Please look at the injectors, lil 1/4" round tag on the side.
Need numbers stamped on and color of tag.
Also, Please post pics of inter-cooler, and blower.
Thx

I would urge you to have a good look at the other head as well. I had the exact same problem a few years back. Dropped the valve while cruising took a week to get home on one engine. The following season the other engine started to show the same smoke. Called my mechanic back to have a look. He said everything was fine. I decided that peace of mind was worth a few bucks so I insisted he pull the head. Sure enough a valve was just starting break apart. We caught it before any damages to the cylinder. Rebuilt the head and went cruising. Best money i ever spent. Of course YMMV.

Agreed.
At least pull the side covers off and send a bore scope up and look at the valves & seats on the other engine.
Lack of use does cause a lil rust stain on the seats. This stain will get hot. Down hill from there.

They will be in your hands soon enough.