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Re: Re-Torquing

Subject: Re: Re-Torquing
Date: Wed, 18 Aug 1999 01:55:17 EDT
A few points I would like to discuss with you.  
First if you drive a car into the shop and turn it off and remove the valve 
cover and start adjusting valves, by the time you get to valve #8 the engine 
has cooled somewhat.  Maybe only 10 or 20 degrees but you have to admit the 
engine is no longer at operating temp. (don't forget not everyone who is on 
this list, can adjust valves as fast as you can, they don't get the practice 
you do :-)  If the engine has cooled by the time you have reached valve #8 
then not all the valves were adjusted under the same conditions.  If on the 
other hand you are working at room temp. the valves will all be adjusted 
under the same conditions.
Secondly, as far as coefficients go, wouldn't you agree that differences in 
expansion coefficients is a function of differences is materials, not wear of 
those items? (regardless of how worn it is, aluminum expands at a different 
rate than iron.) 
BTW one of the engines I teach on has a new valve adjustment spec that 
SPECIFIES 20 degrees C (68F) and has corrections for each 1 degree C variance 
from that temp! (The clearance changes by 0.01mm for each degree C)
The differences we are discussing are small and perhaps, not worth the 
bandwidth, but I like doing my valves cold.
Rick Ewald

In a message dated 8/17/99 7:40:34 PM Pacific Daylight Time, writes:

> In my experienced (and not-so-humble) opinion, valves should always be
>  adjusted when they are hot. After all, they do their work when they are hot
>  and that's when the clearance is critical. Who cares what the clearances 
>  when the engine is cold and at a standstill? And, yes, I know a lot of shop
>  manuals state that clearances should be set when the engine is cold, but
>  they were written when all the valve train components were new and
>  co-efficients of expansion throughout the valvetrain could be relied upon 
>  be fairly uniform. We are mostly dealing with old, worn engines where some
>  things may expand at different rates than others So, if the book gives a
>  "Cold" valve clearance, just subtract 2 thousandths from it and set the
>  clearances when the engine is at running temperature.

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