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17 inch of vacuum rule

Discussion in 'COMP Cams Support Forum' started by fridge, Aug 18, 2018.

  1. fridge

    fridge New Member

    Jan 21, 2016
    can i run a hydraulic cam with a little lash without destroing the cam ? when i leave about .010 lash on the intake my vacuum make the rule but i dont know if i can run with that kind of a lash
  2. A A

    A A Well-Known Member

    Jun 22, 2014
    It isn't advisable, but yes you can run some clearance for a race. Since the plunger isn't limited by the pushrod, you risk the plunger keeper failing in the lifter. A better solution is to run Rhoads variable duration lifters. The Rhoads lifters will prevent any damage and effectively pull off some cam duration at idle speeds for more vacuum. Old drag racers commonly ran hydraulic cams with zero lash (no preload) to avoid lifter pump up at high revs, but the Rhoads lifters also made some track cams idle smoothly on the street in automatic transmission cars. Have a look at the Rhoads V-Max.
    Last edited: Aug 19, 2018

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