[xj-s] Vacuum advance module repair

["Lee Opausky" <Opausky@netcom.ca>]

This may be another subj of interest to people overhauling their
distributor: I have completed a John Napoli described repair of a spare
advance module.  The  flat link assembly  from a module bought for a Chevy
350 did not fit the internal Lucas spring, also the size of the Chevy
assembly inside the Lucas dome did not allow for the full 5/16 " travel
required. ( 88 - 89 non Marelli).
Therefore I fabd a new actuating rod out of a brass rod, treaded at one
end, using the old Lucas washers to hold the Chevy diaphragm compressed by
a nut . This gave me the required travel and a secure fit of the spring
inside the dome.  8 holes drilled into the rim of the two halves of the
bell, a thin layer of high temp silicone applied before sandwiching the
diaphragm, clean up the sharp edges - job done. The unit tests great to
human sucking - full travel.
 Only one concern: even using the smallest bolts ( 3-48 I believe) , the
holes required in the rim of the dome left barely 1 mm metal to compress
and hold the edge of the diaphragm. This is less than 1/4 of the original
compression area, and with the continuos workings of the diaphragm the
rubber is likely to tear, making the whole car less than roadwordy.
Any suggestion to clamp the old Lucas dome together other than drill away
the  surface of the mating rim ?
Kirby indicated recently that he did a vac adv module repair years ago, I
wonder what clamping method he used?     He also mentioned that he used a
piece of INNER TUBE for diaphragm, this really grabbed my interest!  How
did it stand up in the high heat?  Anyway, being a scientific type, I am
now looking at a suitable rubber membrane ( the Chevy diaph is really
fragile looking - maybe Lucas' idea of having a double membrane and fiber
or canvas reinforced has a merit). Medical rubber cut from hot water bottle
or a piece of acid proof rubber gloves which has a fiber mesh backing could
be more heat resistant.
Your constructive comments are appreciated!
Lee Opausky

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Follow-Ups:

• Re: [xj-s] Vacuum advance module repair
• From: "Kirbert" <palmk@mailer.gadcomm.net>
• Re: [xj-s] Vacuum advance module repair
• From: John Napoli <jgn@li.net>

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