hydraulic tappet damage on vw transporter 1.9td correctly timed. engine code:ABL year.1996/7?

Question

cyclinder hd /gasket valves and valveguides and tappets have all been replaced and timing marks aligined. cranked over thru 360degrees etc. but at the point of ignition valve tappets hydrauclic /lock and blow the tops off on no.1&3 . have replaced buckets 3times &the problem still persists.

Answer 1

try here

http://groups.google.com/group/rec.autos.makers.vw.watercooled/topics?lnk=sg&hl=en