[Tigers] Fwd: Restated: Mistake in Performing Tiger's Valve ClearanceCheck

[Rob Hogan]

I'm asking because as I turned the engine toward #1 TDC with a breaker bar
& socket on the front damper bolt, I heard a distinct sound that was like
something cracked.  The source area was indeterminate.  There was a
resistance to continuing with the rotation, but I didn't judge it as a
reason to stop.  Applied torque was probably less than 30 ft. Lbs. I
dismissed the event as not important until the head was removed to check
the valve impressions in the clay. The sound could have been generated be a
number of things, rod, bearings, piston rings, etc.  Among potential
sources, I have no idea of how resistant to damage a rod bearing position
tab is when the parts are only assembly lubed.
I probably should defer to being safe and disassemble the #1 R&P from the
block for visual & magnaflux inspection or not and take the risk and run
the engine as is.

On Wed, Jan 24, 2018 at 9:37 AM, Jay Laifman via Tigers <
tigers at autox.team.net> wrote:

> I’m confused.  Why are you asking?  It sounds like you think you have
> cracks in the pistons because you used clay before and you are considering
> taking apart the engine.  But you are not sure you have cracks, so you are
> asking about the clay.
>
> If that is true, perhaps the first question to be considered is why do you
> think you have cracks?   And if you have them, it would seem irrelevant
> whether or not the clay was the cause.
>
>
> Begin forwarded message:
>
> *From:* Tom Witt via Tigers <tigers at autox.team.net>
> *Date:* January 23, 2018 at 11:58:45 PM PST
> *To:* "Tiger's List" <tigers at autox.team.net>
> *Subject:* *Re: [Tigers] Restated: Mistake in Performing Tiger's Valve
> ClearanceCheck*
> *Reply-To:* Tom Witt <atwittsend at verizon.net>
>
> 1 cubic inch is 16.4 CC’s. The combustion chamber is at least 49cc’s and
> likely larger towards 54cc’s (or more, I don’t have my combustion chamber
> numbers floating off the top of my head). The clay is pliable and would
> only squeeze into a void area of which there is at least three times its
> volume in space. And think of it this way, the cylinder pressure is upward
> of 150 PSI - and that is even before ignition.  My guess it is HIGHLY
> improbable that the clay being offset would cause a piston skirt to crack.
> Push a piece of clay under your finger and see that the finger doesn’t
> bottom out on the surface it is pushed onto with virtually no clay
> underneath.
>
> <image[1].png>
>
> *From:* Rob Hogan via Tigers <tigers at autox.team.net>
> *Sent:* Tuesday, January 23, 2018 9:17 PM
> *To:* Tiger's List <tigers at autox.team.net>
> *Subject:* [Tigers] Restated: Mistake in Performing Tiger's Valve
> ClearanceCheck
>
> BECAUSE approximately a 1 sq. in. small flat of modelling clay was placed
> (not near the piston's periphery) in the squish area of the piston instead
> of only under the head's combustion pocket, would the assembled piston and
> rod's rotation have caused the piston to cant in the cylinder bore enough
> to crack a piston skirt?
>
> Is there any other potential weak area that could be cracked by piston to
> head interference with clay in between?
>
> I hesitate to disassemble the engine to search for possible part cracking
> if the clay interference is really incapable of causing something to crack.
>
>
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