I have had my custom 2.1L WBX running for over 50,000 miles and have yet to
have my lifters clacking upon start up, even after it sat for several weeks
without being cranked.  I have started it for short cranks to move out of
garage and short trips without it being fully warmed up.  My lifters came
from AVP.

Used only Mann/Mahle filters and 20-50 dyno for first 5000 miles and
Synthetic after break in of the engine.

(Now that I said this watch me start having this problem.:-):-()

(I am going to be replacing my lifters with a set of performance lifters
good to 6500 RPM soon.)

Robert