[Shotimes] Re: Knocking update (kinda long)

[Adam Parrott]

The similarities between our situations is so scary, it's almost funny.

I had a brief chat with Tony at his house tonight, and we both agree with
the statements made by Tom, Kirk, et al. concerning possible valve spring
breakage or valve guide/keeper failure.  Unfortunately, it'll probably be a
few weeks until he can tear my baby back down again due to his already full
plate.  When the time comes, the plan will be to tear down one head at a
time (thus minimizing the work involved) and inspect all of the previously
uncheckeable valvetrain components.  If both heads turn out okay, then the
inspection moves to the pistons.  Let's hope it doesn't go that far.

Many thanks to everyone for their help with this issue - I'm sure some of
you are tired of reading/hearing about it.  Once the cause of the sound has
been definitively determined, I'll let everyone know about it.

Best of luck with the repairs on your brother's SHO, Russ.  Please keep us
posted on your findings.

Adam

----- Original Message ----- 
From: "Russ Highton" <russh@corneredge.com>
To: <TechSHO@topica.com>
Sent: Tuesday, May 18, 2004 11:19 PM
Subject: RE: Knocking update (kinda long)

Tom,

I spent tonight working on my brothers car with the similar sound, and I
agree with you 100% in my case.  We re-assembled the engine tonight, and
listened closer, it has to be a valve related noise.  While cranking and
looking directly at the cam and lifters, I could not find a problem.

Valve clearances were fine.  Cams looked OK, not the best, but ok.

So I'm thinking broken valve spring.  I can tell for sure its coming
from the rear-passenger side cylinder, loud and clear.  Now, our noise
is not as loud, but clearly the valve train.

Any idea on how long it could last like this?   My brother is a college
student who can't afford a new car, and can't afford a repair at this
point.

Thanks,

-Russ

-----Original Message-----
From: Thomas Leeth [mailto:tomleeth@charter.net]
Sent: Tuesday, May 18, 2004 3:41 PM
To: TechSHO@topica.com
Subject: Re: Knocking update (kinda long)

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Adam, I went back and listened to your sound clip again.  You indicated
that the noise seems to be present only when the engine is running (nothing
audible during starter spin up).   You indicate that the noise seems to
be top end in nature but hasn't been isolated to a single cylinder.

In my 50+ years of working on cars and being around folks that work on
cars, I have never seen or heard of a catastrophic wrist pin failure.  I'm
sure it could happen due to a defective pin, rod, or piston but would think
it would happen under extreme conditions (like max acceleration launch).
You indicated that you noise suddenly started for no apparent reason.

The sound clip has a deeper clack (knock) followed almost instantly by a
much higher pitch click.  This event pair is periodic (knock-click),
clearly tied to either engine RPM or a submultiple of engine RPM.  I'm a
little surprised that you can't locate the specific cylinder that is
producing the noise,and still think you should be able to locate it with a
stethoscope.

My best bet is that you have a broken valve spring or maybe a valve stem
guide that has somehow came loose and is moving up and down in its bore.
I think the louder, deeper  sound is due to a piston hitting a valve that
is not fully retracted and the second higher pitched sound is the valve
hitting the other end of its free travel (made possible by a broken spring
or guide).

Regards,

Tom Leeth