The geometry IS changed ! the rocker on the pusrod side is 1/16 higher
than it was before...
and moves to a position 1/16 higher when the cam pushes it up.
1/16 no big deal, more ... ?
But I'm sure if you "adjust it" it would'nt be a problem
john.kahoon@juno.com
71 midget
On Mon, 31 Aug 1998 20:29:15 -0400 Bill Schooler <schooler@erols.com>
writes:
>Lawrie Alexander wrote:
>>
>> Hate to jump in a criticize one of Mr. Allen's learned contributions
>but I
>> just gotta........
>>
>> If your head were machined a lot (say 1/16" or more), shims under
>all four
>> pedestals would restore the original geometry.
>
>Okay, I'm gonna jump in here without any of the usual "IMHO" caveats
>and
>say that this business about "changing the geometry of the rocker gear
>when you machine the head" is not correct. If someone proves me
>wrong,
>I'll be the first to admit it and eat crow.
>
>Machining the head will NOT change the rocker geometry. Visualize a
>cutaway, end view of the engine. Now imagine removing 1/16 in from
>the
>face of the head. What has happened? Everything is "lowered" except
>one piece - the pushrod. If we were to remove 1/16 of an inch from
>the
>pushrod, all would be the same as before - with regards to the
>geometry
>of the valve train. Lo and behold, we don't have to machine the
>pushrods - merely back off the rocker adjustment screw to restore the
>normal .15 thou clearance and bingo! Back in business just as before.
>
>
>As a matter of fact, I believe that the geometry would be screwed up
>if
>you installed 1/16 in shims under the rocker pedestals. Then the
>"geometry would certainly be different since you have raised the
>rocker
>arm in relation to the valve stem tip.
>
>I think John Twist has made this point before, but can't find the
>reference...
>
>*Bill Schooler *Check the MGCC Wash DC Centre Web Page
>*Woodbridge, VA *http://members.aol.com/mgccwdcc/
>*schooler@erols.com
>*53 TD
>*60 MGA
>*69 MGB/GT
>
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