[Chevelle-list] valve tap ?

[Jim & Chris]

Thank you for the info .Ineed all the help I can get. I replaced the PCV same tapping noise, I'll time it again and look for vacuume leak ? tahnks again . JimmyC.
  ----- Original Message ----- 
  From: tech 
  To: 'The Chevelle Mailing List' 
  Sent: Saturday, June 30, 2007 1:18 PM
  Subject: Re: [Chevelle-list] valve tap ?


  The PCV valve (positive crankcase ventilation) is designed to remove the harmful blow-by gases in the crankcase. The PCV valve is designed to have "variable flow" which uses manifold vacuum to draw crankcase vapors into the intake manifold.  During idle, manifold vacuum is very high and blow-by pressure is very low - the pintle inside the valve will retract against a spring and only allow a small amount of blow-by to enter the manifold.  If the spring pressure is nearly equal to the force on the valve from the vacuum the pintle will bounce and make a rattling sound.  This can happen if there is low manifold vacuum at idle due to a long duration camshaft or late ignition timing - or the spring in the valve wore out.

  Replace the valve.  You'll pay around $3.00.

          Granite City Performance 
        custom engineered competition components  
    


   

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  From: chevelle-list-bounces at chevelles.net [mailto:chevelle-list-bounces at chevelles.net] On Behalf Of Jim & Chris
  Sent: Friday, June 29, 2007 11:04 PM
  To: Chevelle Forum
  Subject: [Chevelle-list] valve tap ?


  I have what sounded like a valve tap,and when I touched the valve cover it felt like a rocker arm was tapping against it so I snugged the rockers , replaced the valve cover and started the motor it was less noisy . when I looked closer I noticed the PCV valve that I had not plugged back in was making the tapping noise. I disconnected the PVC from the vacuum hose while the car was still running,when I put my thumb over the vacuum hose I noticed the vacuum was intermittent causing the PVC to make the tapping noise. What would cause the vacuum to fluctuate so rapidly ? I was using the vacuum port on the back of the carborator for the PVC. sorry about running on.any advice is appreciated. Jimmy C.
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