[DeTomaso] Exhaust Valve Not Closing?

[Art Stephens]

Asa Jay,
     It's not backfiring.  In fact I was hoping it was just an exhaust leak, 
which it kind of sounds like. (Probably just wishful thinking).  The last 
time it did it,  I pulled over while it was still making the noise.  I got 
out and looked it over with the engine running.  I couldn't see any obvious 
problem so I got back in the car and drove  home.  As soon as I drove away, 
the noise stopped.  I'm pretty sure it has the original hydraulic lifters 
though it appears that the heads had been off at one time.  Aren't hydraulic 
lifters supposed to work like solids after they are pumped up?  A lifter 
can't grow can it,  beyond its full normal height?  I wonder if I just 
slightly bent a valve when I missed the shift and maybe that valve moves 
fine thru its guide until it gets hot from the heavy load of accelerating 
hard?  Perhaps the additional heat is enough to make things expand to the 
point that the spring can't pull the slightly bent valve all the way down to 
the seat?  Maybe it starts running ok again because I slow down and let 
things cool off at which point the clearance between the guide and valve 
increase?

Thanks,
Art


----- Original Message ----- 
From: "Asa Jay Laughton" <asajay at asajay.com>
To: <detomaso at realbig.com>
Sent: Sunday, May 31, 2009 4:00 PM
Subject: Re: [DeTomaso] Exhaust Valve Not Closing?


> Art,
>
> Is it backfiring out the exhaust?  If not, then the valve is probably
> okay.  Something in the valve train though?  Maybe.  It might be you
> stressed a lifter, are they hydraulic or solid?  Maybe bent a pushrod?
>
> Seems to me if it's running fine until you run it hard (presuming higher
> rpm), then I'm betting a lifter problem, one that can't keep up.
>
> Asa Jay
>
> Asa Jay Laughton, MSgt, USAFR, Retired
>
> & Shelley Marie
> Spokane, WA
>
> 1971 Mach I Mustang  [ASA JAY]
> 1973 Pantera L 5533  [ASASCAT]
>
> ******************************
> http://www.asajay.com
> http://www.teampanteraracing.com
>
>
>
>
> Art Stephens wrote:
>>      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?  Any ideas as to what is 
>> going on?
>>
>> Thanks,
>> Art
>>
>>
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