<VV> Is it a knock or tap?

[Russ Moorhouse]

I put my car in the garage in mid December.  It was running great at that 
time.  Today, it got up over 70 degrees, so I thought I would start it up 
and drive it a bit.  I primed the fuel pump by pushing up and down on it a 
few times and the car started right off the bat.  The valves made their 
usual clatter at first but settled down, except for one loud tap or knock.

The engine ran rather smooth, with no obvious misses, which leads me to 
believe that it's not a lifter, but on the other hand, how would I develop a 
knock in the engine while sitting in the garage for 3 months?  And if it is 
a knock, where should I look for it?

Russ Moorhouse
'65 Corsa coupe 140 HP
Group Corvair Member
Corsa Member
Kent Island, MD