Valvetrain(?) ticking until warmed up

Backing out of the garage yesterday I heard a ticking noise that initially reminded me of the sound one hears from the injectors in a batched EFI (e.g. L-Jetronic) system; I wasn't alarmed because I know that the lambda feedback on my Mondial 3.2's K-Jetronic is implemented via pulsed control of a solenoid valve (not unlike an electronic fuel injector), and immediately assumed that's what I was hearing. (The car is new enough to me that I wasn't surprised to be noticing a normal sound for the first time.) Several hours later, I'm back in the garage after a fairly lengthy errand (>150 mi round trip), performing the air conditioning recharge that a smart person would have done *before* setting out for a lengthy drive in 80°F weather. The car has been sitting for roughly an hour, but it's still warm, at least in terms of human discomfort associated with leaning over the engine and reaching one's hands down to the aircon service fittings. Again I hear a loud ticking at idle, seemingly coming from the forward cylinder bank. Unfortunately I was focused on recharging the air conditioning, so I didn't get out the stethoscope or do anything else to chase the noise, besides putting a (gloved) hand on the valve cover and not noticing any particular vibration that would correlate with the noise.
By the time I finished with the aircon and returned my attention to the ticking noise... it was gone--seemingly a function of the engine getting back up to operating temperature. However, if I revved the engine slightly, the noise would come back--seemingly much less pronounced than before, but also somewhat drowned out by other engine noise, so hard to tell.
Any thoughts as to what I'm hearing here? Besides my initial thought that (from the driver's seat) it reminded me of batched EFI (if you stick your head in the engine compartment of such a car), I could also say that it sounds like what you'd hear if a car with self-adjusting cam followers has a collapsed one. So am I just hearing excessive clearance on one follower? Why would this noise suddenly become noticeable?

Thanks in advance,
Joe ('86 Mondial 3.2 Coupe)

 

I was actually going to try a product I happen to have on hand that’s actually called “belt dressing”—seems like the right tool for the job—unless you guys really think that these unique belts warrant an actual lubricant.

Thanks again!

 

Well, I drove the car again today, so I took the opportunity to lean over the engine with belt dressing, WD-40, and stethoscope in hand both right after the cold start, and again after ~45 min of running errands. And... no ticking noise; not when cold, not when warm, not with the aircon engaged, not with the aircon off, not at idle, not revved up a bit.

So, while totally inconclusive, I'm increasingly inclined to believe the belt theory; I can't think of anything else that could be so intermittent. The other clue here is that I recently changed the belts, and 1) I don't have any previous experience with these oddball wide-angle plasticky v-belts (and the manual only specifies tension for the water pump one) so I tensioned it as though it were a conventional 40° v-belt, and 2) the "new" belt I installed came with the car so I don't have any idea how long it had been on a shelf somewhere.

Depending one what kind of resonance I might have been able to pick up with the stethoscope, I'm skeptical if I ever would have successfully isolated this to a snapping belt on my own, without your suggestions; I probably would have been perpetually worried about driving the car, and maybe even removed a cam cover out of paranoia! Thanks, guys!!

 

Follow-up question: How tight do these PolyFlex belts want to be, compared to a conventional v-belt? (Between the wider contact angle and Gates’ marketing of “high modulus polyurethane,” logic suggests they should be somewhat tighter, but I was reluctant to go there when I changed the belts; I’ve seen too many water pumps destroyed on other cars when doofus mechanics over-tension v-belts.)

 

That picture is different than my belt configuration, but dang--I didn't realize that this information would be in the Owner's Manual--that was a silly oversight!

Here's what I've got in the owner's manual:
Image Unavailable, Please Login

It refers only to the Gates 150 tool, and doesn't provide the alternative force/deflection method for the aircon belt, so I'm probably just going to tighten it by one turn of the adjuster and keep an eye/ear on it (I didn't really want to have to take the fender liner and belt cover off, anyway). Is there an equivalent to the Gates 150 tool? If I understand correctly, it looks a lot like Porsche special tool #9131, but the Porsche tool doesn't have a scale, per se, just one notch with which the pointer lines up when the timing belt on your 928 is correctly tensioned.