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
|