Clicking / Snapping Sound from Dash in 85 Caprice

I have an 85 Chevy Caprice with 343,000 miles on it ( yes 343,000) . Suddenly, I am hearing a clicking / snapping sound from the center / right of the dash
during acceleration, and also sometimes during deceleration, and also when in Park, at about 1500 rpm.
At fisrt, I thought my spark knock was coming back, but a spark knock doesn't occur in neutral, and during deceleration. So I am thinking it might be : u-joint... transmission... distributor... exhaust... or speedo (but would speedo click in Park?)
I can't see anything unusual under the car or in the engine compartment.
ANy ideas welcomed ! Thanks
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Any possibility that you're hearing spark arcing through a bad boot from the dizzy to the firewall? You'd certainly notice the misfire, and Caprices are pretty cush cars with lots of sound insulation that should dampen such a 'small' noise, but it's an idea.
On Fri, 05 Dec 2003 06:38:51 -0700, Lecher9000 wrote:

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Thanks for the idea. There is no misfire, though. The car runs fine, I jus thave this clicking / snapping sound. Lately I think it might be air trapped in the heater core. I had a coolant leak at one of the htr hoses a few days ago. I tightened up the leaking clamp, but the noise is still there. Maybe just taking it's time getting the air bubbles out. I hope.
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