<VV> Unknown screech noise in/on engine

[Daniel Monasterio]

       After 37 years dealing with vairs, I found a new (to me) noise. Just 
after changing spark plugs (Autolite 425) the engine began to make a 
constant screeching noise, like moving a metalic cap (like old fashion soft 
drinks) on a flat glass. The noise is constant with the engine ruuning. The 
pitch is really high. Took off the belt for isolating alternator, belt 
tensioner and fan bearings with no change. The noise pitch is different from 
dry rocker arms, dry valve stems or a loose bellhousing bolt against the 
flywheel.
      Think that changing plugs had nothing to do and was just coincidental. 
Engine is a 110 with less than 2,000 miles, no oil comsuption, no oil smoke.

      Would somebody point me on what can cause this noise ?.... thanks in 
advance for any help.

      Daniel Monasterio