seems impossible to find the 261 cam lobe flank and opening ramp shape online
but for a rough estimate (maybe i screwed this up...):
assume it is an raised inverted sine shape and using 0.42 maximum valve lift for a modified 261 cam
the first 5.5 camshaft degrees of rotation would only lift the valve by about 0.002-0.010 inches of travel,
in a cold engine with max valve to rocker clearance, the valve might not even begin moving until the piston reaches near or at TDC.
could put the engine together with a carefully placed blob of putty on the piston, and rotate the engine slowly
pull the head and measure the clearance
-s
