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. However, they would surely be
classified as four "thick" shims. The two originally fitted to later 5-main
engines (after 1968, I believe) were actually quite skinny - from memory,
I'd say about .010" at the most.
No-one really knows why the factory decided to put them there (unless Mr..
Cairns has some wisdom for us?) but they were, indeed, fitted only under the
center two pedestals.
Going back to the original question, however, there never were gaskets under
any of the pedestals. The one that Hicks found must have been an ill-advised
effort by a DPO to prevent oil leaking from the pedestal that supplies oil
to the rocker shaft.
Lawrie
British Sportscar Center
-----Original Message-----
From: Robert Allen <boballen@sky.net>
To: Hicks <hicks@mohawk.net>
Cc: mgs@autox.team.net <mgs@autox.team.net>
Date: Sunday, August 30, 1998 9:27 PM
Subject: Re: Valve rocker to head assembly.
>Hicks wrote:
>
>> I am reasembling the rocker assembly to the head and remember at least
>> one gasket under one of the rocker posts between the bottom of the post
>> and the head. . I can't seem to find it in my parts. Very thin gasket
>> like material. I think it was on the post that has the oil passage way
>> in it. Anyway, none of the manuals that I have comment on this gasket.
>
>Well, this may not apply, but when skimming the head or the block to get a
>little more compression, you effectively move the rocker shaft closer to
the
>cam. This messes up the desired pushrod geometry a little. If a significant
>amount of material is removed (say 20 thousands -- about the thickness of a
>matchbook) you're supposed to add metal shims of the same thickness between
>the rocker tower and the head.
>
>Do you know the history of your motor? Is compression higher than expected?
>
>If you're not looking for four skinny shims, one under each rocker tower,
>then Chris is right, two thick shims were specified as stock.
>--
>Bob Allen, Kansas City
>
>
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