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I had the exact same problem. It seems to me that there should be an easier way to guard against a head that has been decked into uselessness.
The clay test is a bit of a pain. Does anyone have an no's head or an undecked one they can mic? I'll measure mine and put it on here. This would give at least some guidance as to how close the head is to uselessness. For example, if the head is supposed to be 1.5 inches thick, and a 1.4 works, then we know that a bad one is something less than 1.4. Over time, we can determine a thickness that is closer to head ruination. I think it's worth the effort, as there are a lot of posts about blown head gaskets.

There are too many variables involved than simple measuring the head thickness. For example, if newer thicker valves, there would be less clearance than valves that have been ground a couple times, especially if the seats have been ground too. Then there's cam lift which I believe differs between solid and hydraulic lifters and also just the basic shape of the combustion chamber may have variances from head to head. The best you could get by measuring the head thickness is that it MIGHT clear but not that it will.

Good points all, but doesn't that make head thickness a better indicator? If I put a new cam and new solid lifters in (max valve height) and then put a skinny head on it, there is real danger of disaster. On the other hand, a skinny head on a used engine would probably not be a worry. Hydraulic lifter engines would of course between these two extremes. It would also make a difference in buying a head. I would think a skinny one would be worth less because of these potential problems.

Good points all, but doesn't that make head thickness a better indicator? If I put a new cam and new solid lifters in (max valve height) and then put a skinny head on it, there is real danger of disaster. On the other hand, a skinny head on a used engine would probably not be a worry. Hydraulic lifter engines would of course between these two extremes. It would also make a difference in buying a head. I would think a skinny one would be worth less because of these potential problems.

Direct measurements better than indirect. Using a depth gauge to measure the height of the combustion chamber over the valves is a direct measurement of what you want to know. Measure each chamber over the high point of the valve lift. Compare that to the height the highest valve lifts above the deck, factor in a compressed head gasket thickness and you should have your answer.

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