alfa twin cam

[bruce plecan]

At 174,000 miles when you do a valve job, the combustion chambers are
then better sealed.  With the rise in compression the rings have a habit
of giving up.  Especially since the engine runs so much better, and the
temptation, is overwhelming to buzz the motor a little higher.  
  Back in the late 70's did alot of ring jobs for fiats whose owners did
the valves, and then brought the them in for the bottom end, several 
months later.  The tempation for doing the valves can be high since that
is so easy to do.  But, the rings have had a bunch of thermal cycles,
and moved up+down twice for every time a valve opened.
  IMHO  Bruce