[alfa] Spider Noise

["Roger Hambro" <rhambro@xxxxxxxxxxx>]

Can you guys help me identify an engine noise in my Weberized '78 Spider?

Sounds like a valve tapping sound that increases with engine speed, but
occasionally misses a beat.
Tap-tap-tap-(quiet)-tap-tap-(quiet)-(quiet)-tap-tap-tap-tap.....   When
cold, the tapping has more (quiet) beats than taps and as it warms, the
tapping is very regular with fewer (quiet) beats.  Most noticeable while
idling and fairly loud.

I've listened with an auto stethoscope and cannot seem to locate the source.
In general it seems louder at the top of the engine than at the bottom but
this is not definitive.

It is not external physical contact of parts.  Rocking the engine a bit
while running has no effect.  I cannot feel the tapping by placing my hand
on various parts of the engine while running.  Disconnecting individual plug
wires while running has no effect on the tapping sound.  Timing chain is
tight.  Valves are set and verified at a little tighter than spec: 0.018"
Exhaust and 0.016" Intake.  

Ideas?  Diagnostic tips?

Thanks,
Roger Hambro
'78 Spider
Algonquin, IL
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