E28 Head Noise

[mike.safford@xxxxxxxxxxxx]

Recently, my 88 528 started making an ugly noise until it completely warms up. And then, once in a while even then.
Intermittently/randomly there is a "clanging" or sound that gives me a visual of a valve hitting a piston.. (backyard mechanic/enthusiast here...)
The car seems to run fine, and doesn't really seem to "miss" even when the noise is present. (Well, maybe just a very little once in a while) 
Again, there isn't any real rhythm, it's random. 
Sometimes a few in a few seconds, sometime one or two in thirty seconds or so. It's relatively loud. Louder than noisy rockers.
Can sticky valves be THAT sticky? Teeth on the timing belt?
I'm not running it until I look under the valve cover, but it's still a bit cold here in N. New England to do much with it in a "no heat garage"..

Any ideas appreciated..

~Mike
Mike.Safford@domain.elided

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