There's a simple way to check the cam timing.  Neither advanced or
retarded is "split overlap".  The exhaust and intake are open the same
amounts at exhaust stroke TDC.
  With cyl #1 at TDC on compression,  loosen the rocker adjustment for cyl
#6 to just barely zero clearance.  Turn the crank  one turn, to TDC for cyl
#6 on compression.  The large clearances on the rockers of cyl #6 should be
the same for intake and exhaust.  You will need a distance piece or a stack
of feeler gauges, to measure.
  If the TDC mark on the damper is questionable, you can check it with a
"stop bolt".  I've made them with an old spark plug.  Break the porcelain
out, and weld a  nut inside.  Round the end of a bolt to give you something
to bring the piston up against safely.  Carefully turn the engine, till the
piston contacts the stop bolt clockwise and mark the damper.  Than turn
counterclockwise, and do the same.  TDC is exactly half way between these
marks.
"Michael Mudd" <mmudd@worldnet.att.net>  jun 2003
`:wq!