[Vwdiesel] swapping a good head - DIY head prep??

[James Hansen]

>   Back to yours though.  If it's tapping then you have one of two
> issues, valves are "too long" from grinding the seats and/or valves,
> or the cam timing is off.

Or there is a cracked valve spring (One of three issues?).  Doubtful the
springs could get so weak they can't bring the valve back, but if it just
taps at speed, weak springs can do this.  Broken spring can do this in
spades. Weak springs usually just eat up the cam from the follower bouncing
off the nose of the cam, and hammering back down. If it's just one valve, it
may very well be a partial coil of the valve spring is broken off reducing
seat pressure to the point that the valve is too slow to close.
-james