Stag new motor woes

[Lawrence G Miceli <lgmtr6@domain.elided>]

I am sorry to say that the motor in my freshly restored Stag has
developed a top end knock after about 100 miles of break-in driving.

Oil pressure is steady at 40 lbs. I removed the valve cover to check for
oil flow  which is excellent (making a great mess of my once clean engine
bay).

The motor slowly developed a slight tick tick, sounding like a poorly
adjusted valve. This noise gradually worsened until I decided it wasn't
going to heal itself. I checked the valve  clearances which seemed fine
and have now removed the cam from the offending head (left side). The 5th
journal appears to be burnished (dark in color) however, the passage is
now clear and oil pumps from the hole when I prime the oil pump with an
electric drill.
All of the valve cups are fine and the shims have not broken. 

Notwithstanding, I do not know that this was the cause of the knock.
Someone else has suggested that a valve seat is coming lose. Is this
possible? Wouldn't a fallen valve seat cause a catastrophic failure?
Could it be a broken valve spring?

BTW, the motor was running great. Smooth at idle and at speed. Plenty of
power (although I have not exceeded 3000 rpm yet due to the break in of
the motor). 

I am looking for suggestions before I go to the time/trouble of pulling
the head. 
 
Larry Miceli
'73 Stag
'66 Herald

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