Problem.

I have a 1990 na RX7 with a strange problem.
For a long time now , and at infrequent intervals, when started cold the
engine would make a gentle "tick, ...tick, ...tick" noise -  like the sound
made by holding a playing card against the spokes of a slowly rotating
bicycle wheel or as though the fan blade were just brushing something in its
rotation. This only occurred when the car was started cold and went away
when the car warmed up. Also it  only happened sometimes, usually after the
car had not been driven for a long time. The noise seemed to be coming from
the front of the engine - the fan/belts area.
Recently the noise has become louder, happens on every start,  and does not
disappear when the engine warms up.
I have no idea as to the cause of the problem but it has reached the stage
where something must be done.
Any of you experts out there ever experienced a similar problem or have any
ideas as to the cause?
Any help would be appreciated.