Thunderbird 1700 Storm Engine

I've owned my T'Bird Storm since new in 2013, I have noticed a "tick" at low RPM's especially when the engine is cold, I have not figured out what the noise is, or where it comes from, There is a small hole in the CAT that allows condensation to drain that I have suspected but I'm not positive. The main thing is I haven't had any adverse problems in over 27K miles.

 

Some of these bikes have the hydraulic lifters and need to pressurize when starting. May just be that.

 

The Thunderbird definitely has solid lifters, I've adjusted my "valve lash" so I can assure you of that. BTW, these engines have " decompressors" on the out side 2 exhaust valves, they work using small weights on the ends of the cam that hold 2 of the exhaust valves open slightly during start up, the weights and springs are similar to the old advance set up on auto distributors so maybe what we are hearing are those weights, decompressors opening and closing at low RPMs?