One could make the argument that the bolts that "need" to be retorqued have
already broken loose.
Anyway, I was once told that retightening the head necessitated a
readjustment of valve lash. Is this true?
Bob Donahue (Still stuck in the '50s)
Email - bobmgtd@insightbb.com
52 MGTD - NEMGTR #11470
71 MGB - NAMGBR #7-3336
----- Original Message -----
From: "Bullwinkle" <yd3@nvc.net>
To: <mgs@autox.team.net>
Sent: Wednesday, September 03, 2003 12:29 AM
Subject: Re: head retorquing question
> There are two types of friction: Static and sliding. Static friction
> represents the force needed to get a stationary object moving. Sliding
> friction is the force necessary to maintain that movement.
>
> General science and high school physics classes teach that sliding
> friction is almost always less than static friction. We pulled weights
> using spring balance scales to measure and test the concept.
>
> An engineering reference shows that hard steel against hard steel has as
> static friction of 0.78 while sliding is 0.42. That means the force
> necessary to start movement is almost twice the force necessary to
> maintain the motion. All cylinder heads that I am aware of have steel
> washers under the nuts. Thus it makes no difference what material
> the head is made off.
>
> Therefor when retorqing, back off the nut using a breaker bar, or beam
> torque wrench, just until it breaks loose and no more. You do not want
> to loosen it completely. Then torque it back up to the recommended
> setting. Do each nut separately and in the same sequence as recommended
> by the engine manufacturer. That is, back off number one and retorque
> to the recommended setting. Back off number two and retorque to the
> recommended setting, etc.
>
> Blake
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