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

Tom Witt atwittsend at verizon.net
Wed Jan 24 13:22:20 MST 2018 

Is the engine on a stand, or in the car? If on a stand you can pull the oil pan. In fact on the Tiger it isn’t even too hard to do in the car. Is it possible..., (short story) years ago I remember a guy telling us about a collective neighborhood rebuild on a guys car.  When they went to start it the engine wouldn’t turn over. Eventually the engine was torn down only to find a block of wood used to prevent crank rotation when tightening bolts had been left inside. And when you say you heard a “crack” sound ... well ... .  BTW, assembly lube is more than sufficient to handle an engine being turned over by hand.

From: Rob Hogan via Tigers 
Sent: Wednesday, January 24, 2018 10:12 AM
To: Jay Laifman 
Cc: Tiger's Den 
Subject: Re: [Tigers] Fwd: Restated: Mistake in Performing Tiger's ValveClearanceCheck

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 
    Sent: Tuesday, January 23, 2018 9:17 PM
    To: Tiger's List 
    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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