[DeTomaso] Exhaust Valve Not Closing?

[Art Stephens]

Jack,
     I like your suggestion of a bent valve wearing enough clearance in the guide.  Along those lines,  that's where I'm thinking a heavier valve spring would close the valve that is giving me trouble?  The old car has a rev limiter on it which will be going into the new car. If I'd had the rev limiter set a little lower,  I probably wouldn't have needed a new car.  :-)))

Art

 
  ----- Original Message ----- 
  From: JDeRyke at aol.com 
  To: artstephens at verizon.net ; detomaso at realbig.com 
  Sent: Monday, June 01, 2009 12:09 PM
  Subject: Re: [DeTomaso] Exhaust Valve Not Closing?


  In a message dated 5/31/09 3:56:11 PM, artstephens at verizon.net writes:


    A couple weeks ago I missed a shift and surely over revved the engine.  The engine was making all kinds of racket for a couple minutes and then the noise stopped.  Hmmm?  The engine runs fine till I run it hard and then it sometimes does the same thing again.  It sounds to me like an exhaust valve is not completely closing? 


  With over-revved 351-Cs, an exhaust valve most often contacts a piston top, and bends the stem a little. Depending on where up the stem the bend is, the valve may stick in the guide (until it cracks the end of the guide or wears itself enough clearance). Or, a pushrod may have bent from the same contact. None of this will show up on a compression or leak-down test. In the case of a pushrod, you may find one is looser than all the others by only pulling the rocker covers and rotating the engine progressively for TDC on each cylinder while twiddling each pushrod or rocker, rather than doing a complete teardown. If you're lucky- and you're certtainly due for some GOOD luck, my friend! Incidently, a rev-limiter is cheap insurance on any Pantera.... Cheers- J Deryke


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