hi guys, just managed to get my 20xe corsa on the road after numerous probs with driveshafts etc. anyway, drove a mile down the road and a REALLY loud tapping noise started from under the cam cover. not just normal tappet noise but sounds like a tractor!! the lump has just been rebuilt with new tappets, it sounds like a tappet is just being slapped about its bore with no cushion on it whatsoever. any ideas?