[Shotimes] Re: Audio clip of knock (was: Knocking help needed)

[Adam Parrott]

I actually tried removing the plug wire removal trick the night that the
sound appeared, but the sound never changed intonation and was present
during the entire test.  This is what lead me to believe that the problem
wasn't ignition or even bearing related, but possibly valvetrain.
Excellent idea, though .. too bad Sergio beat you to it.  ;)

Looking back on my previous postings, I find that I also need to correct
myself.  I had stated that my bearings were changed at 135k, however this
was the mileage for my ATX rebuild, not the bearing swap.  The rod bearings
were actually replaced 137,730 miles last December 15th by Tony Huerta.
Assembly lube was used on the new Clevite bearings and the crankcase was
refilled with 5 new quarts of Castrol GTX 10w-30 afterwards (the same oil I
always feed it).  At 138,305 miles, the oil and filter were changed again
to get rid of any metal particulates and the assembly lube that was used
during installation.  Only five of the six upper bearings showed any copper
wear (less than 1/4" inch total area) and were in good shape for 137k.

I guess the long of the short is that I can't really see how
properly-installed, new bearings could fail in such a short amount of time
or mileage (7k miles), especially given the excellent history of my engine.
I do agree that the problem is most likely not accessory related, but I am
leaning towards something in the valvetrain (having not made use of a
stethoscope yet, my ear tells me that the sounds is loudest near the #5 and
#6 cylinders on the top-end .. possibly chain or tensioner?).

Regardless, I apprecaite all the help and suggestions thus far and continue
to welcome any additional thoughts that people may have.  Extra thanks go
out to Chris Mayfield for suggesting a few other possible "options" that I
need to look into once the weather clears up.

Adam

----- Original Message ----- 
From: "George Fourchy" <krazgeo@comcast.net>
To: <TechSHO@topica.com>
Sent: Saturday, May 08, 2004 5:16 PM
Subject: Re: Audio clip of knock (was: Knocking help needed)


On Sat,  8 May 2004 12:24:59 -0400, Don  Donelson wrote:

>I agree with u locating the source.
>
>One way is to do the stethescope ... but its sounds as if its coming from
the lower end ... and it sounds like rod bearings.

You might be able to isolate the sound by removing one plug wire at a time
from the coil pack.  Do it while the engine is stopped so you don't shock
yourself.  If it is a rod knock, the sound will be different when that
cylinder is dead, when the plug doesn't fire.

I've only heard one bad rod in a SHO engine....in the black car I have when
I first drove it onto the trailer to take home from where I got it from,
and then into and out of the shop where I first tried to swap it with
another engine.  The sound was a LOT deeper, and rang like a bell, as the
crank was being pounded against.  This doesn't sound like that to me at
all, but as I say, I've only heard one bad rod, and it was REALLY bad.

I sorta don't think it is the accessories, but it is easy to check.  Maybe
it is a bad timing chain tensioner in the back of the engine letting the
chain flop around, or maybe one of the sprockets back there is bad.  I
can't think of what else it could be.  It sounds like a really bad tappet
in a pushrod engine....that's the closest thing I can think of that it
reminds me of.

Let us know what you are able to rule out.

George