Engine noise

[siwes]

My 500 griff is a bit noisy! good oil pressure when hot 40 psi at 2500 rpm but to my ear it sounds Tappity !! at times worse than other , my question is : is it the followers I can hear? if it is is it an easy job to change them .
any replies greatly appreciated.
by the way the car has had two services at Blackpool and they have never mentioned the noise , so are they ( the serpatine engines) noisy?
regards Simon