Any ideas what could be causing an annoying tapping noise on my engine I have replaced a faulty exhaust camshaft due to cam shaft lobe breaking up plus replaced the chain and tensioner as a matter of course. All the valve clearances are correct but the tapping seems to be in time with piston stroke. Some suggestions have been piston slap, can anybody else throw some more light on this noise. The noise all but disappears when the engine gets warm and it runs fine and doesn't use a drop of oil