[DeTomaso] Exhaust Valve Not Closing?

Mon Jun 1 11:37:32 EDT 2009

Asa Jay,
     It sounds to me more like exhaust or an exhaust leak as opposed to 
clattering or ticking.  I guess at this point,  I would be putting my money 
on an exhaust valve that is not closing?  I guess it really wouldn't be that 
much trouble to replace a valve spring or four before the trip?

Thanks,
Art


----- Original Message ----- 
From: "Asa Jay Laughton" <asajay at asajay.com>
To: <detomaso at realbig.com>
Sent: Sunday, May 31, 2009 9:39 PM
Subject: Re: [DeTomaso] Exhaust Valve Not Closing?


> I'll have to let the more experienced brains on the list jump in at this
> point.  But if the noise is there one minute, then you let the car
> breath for a while by not going anywhere, and then it stops.... it
> sounds like a lifter is starving.
>
> Yes, hydraulic lifters pump-up, but that doesn't mean they -stay- that
> way.  At high rpm, you might be getting some bleed back which is
> allowing the lifter to collapse.  My bet would then be a slightly bent
> pushrod.  Follow my on this.
>
> At high oil pressure when the lifter is pumped up, the clearance on the
> pushrod is taken up and you have no noise.  As the oil warms with high
> rpm, you get just enough bleed down on the lifter to open the gap on the
> pushrod and you start to get some clattering, or ticking.  You let off
> and the process reverses.
>
> Of course, I honestly could be all wet on this idea too.  I've not
> built, trashed or have quite enough experience to know for certain.  But
> I enjoy learning from everyone on this list.
>
> Let us know what you find,
> 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:
>> 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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