My '91 Miata (170k miles)has just begun making an ominous clicking/rattling sound at lower rpms--at higher revs the noise is not noticeable, but at lower revs the clicking can be heard--it seems to be emanating fom the right front of the valve cover (maybe the nose of the right cam?). The car was professionally maintained until I bought it (14 mos/35 k miles ago)--since then I've changed the oil regularly (every 3,000 mi). i just noticed this for the first time a few minutes ago, and have not had the opportunity to delve further. Any likely causes? Any info would be appreciated.
Regards,
brentlewiis3000