[johnta1]

Here's a quote from Larry Meaux:

if the FPS thru a Pushrod Pinch is way too fast ( too small CSA )
then it reflects back a positive pressure Wave against the incoming positive pressure wave disrupting and somewhat blocking incoming Mixture Flow to the Cylinder, and even worse bad effect is now the Total Induction path seems shorter , and changes the best acoustic wave pressure timing at the Intake Valve closing point ABDC

if you have a too fast Floor Apex area at the beginning of the Short Turn Curve it will cause Fuel separation out of the incoming flowing Mixture and also can cause Flow Stall
... that is , Dry(Flowbench) or Wet( Live Engine) Flow separation from the Shape of the Floor's Apex area thru the Short Turn Curve Shape and some Flow will shoot across the Curtain area opening towards the Long Turn ... blocking or hindering any further Flow CFM gains ( Flow CFM Stall or Flow CFM reversal effects )
........you want to use the entire Valve circumference Curtain area for maximum Flow CFM , and not Flow separation causing a portion of Flow to shoot across the Curtain Area blocking Flow CFM

The worst situation is :
you can loose a lot of HP around Peak HP RPM point and above
if you have a "combination" of both a too fast Pushrod Pinch area and a too fast Floor Apex area at beginning of the Short Turn Curve

on NHRA SuperStock SS/IA 362cid at 7500 RPM and above RPM , it lost over 105 HP in a #041X casting 164.0 CC Port Volume Port at 250 CFM at 0.700 Lift and ran 10.80's at 3330 Lbs

a likewise pair of the same #041X castings, again with 250.0 CFM at 0.700 Lift and 164.0 CC Port Volume but this time reshaping Ports with grinding + epoxy , it set NHRA SS/IA Record at 10.132 ET

10.132 ET from 10.80's

The Pushrod Pinch is typically located 4" or inches before the Intake Valve(which is basically the end of the Induction Path) , so a too fast Pushrod Pinch can hurt you more than a too fast Floor Apex/Short Turn Curve area by changing Tuned Length.... but a combination of both, by far, can cause a severe HP lost !

He also says that the Pontiac heads are really bad with their pushrod pinch. (and long port length probably)