Could anyone give me some advise please. On a 3dr cos with original engine although only done 49,000 miles & has a bottom end rebuild at some point. Since i've had it the head has been stripped & rebuilt with new guides etc. The engine does not smoke & burns very little oil ( about a litre to every 2 or 3000 miles ). It has piston slap from cold but this goes after about 5 mins once warmed up. For a while now it has had slightly noisey tappets or so i thought, has for the last few months seemed like it has had 1 really noisey tappet that will sometimes go quiet & then will start being noisey again say if the car is at idle & at full working temp the tappet sounding noise will be their one minute & then will stop making the noise for a while then come back again. Got my local garage to change the followers yesterday, its a definate improvement now when started from cold noise wise but this noise i have described above is still their, to me it definately sounds like its coming from the top end like 1 sticking/noisey tappet as the noise comes & goes but all new followers ! I use Castrol 10-60 oil & the guy at the garage told me this is far to thin & if i were to use a thicker oil (semi synthetic) it would most proberly stop the noise. I know the other way to stop it is to strip the engine and rebuild it ! But that seems a bit drastic as it doesn't smoke & burns hardley any oil. Anybody got any ideas about using slightly thicker oil or what the noise could be ?

Thanks Simon.