Re: Dist Vacuum Advance Problems

[jlandry@domain.elided (John A. Landry)]

In a brilliant stroke of genius, "Eppinger.Michael"
<Eppinger.Michael@domain.elided> blurted out:

>He listed as one of the problems, as being a "weak" distributor vacuum
>advance unit.  Is there anyway to fix this or just simpler to replace?

Epp,

I've pried open and worked on several of these vacuum advance units.  After
doing a few I'm getting good enough to where you can hardly tell I've
opened it.  I use a bench vise and a large pair of channel locks to do the
job.

Once open, you will probably find a torn diaphragm.  Depending on where the
tear is, you can sometimes seal said tear with liquid rubber or preferably,
a *thin* film of silicone sealant (black in color to be Landryesque about
it).  Replacements are about $35.00 and most auto parts stores can order
them without difficulty.  Due to the expense and lack of the need to trade
in a core, you might try rebuilding it yourself a shot.

>I guess the vacuum unit is not appling enough advance to the
>distributor.  The dist is remanufactured, and this is the first
>installation of it.  I can't remember if the vacuum advance came with
>the unit or if I pirated it off of another dist.  This is a Prestolite
>points dist.  Would a prestolite electronic dist vac advance work?  What
>about one off of a holley dist?  What about an adjustable one from

The Holley and Prestolite advances are not compatible, but if you're
ingenious enough, you can swap and fabricate internal parts.

Come to think of it, if your mechanic is saying you're not getting *enough*
vacuum advance (but it's not leaking down), then you might try this: See if
there is a threaded reducer on the end of the vacuum advance unit (where
the vacuum hose fitting threads on).  If so, unscrew it to reveal a spring
with washers underneath.  Remove some or all of the washers.  They serve to
put more tension on the vacuum advance spring and delay application of the
vacuum advance.  Otherwise, the *amount* of vacuum advance cannot be easily
changed by you.  You have to disassemble the vacuum advance unit and modify
the connecting arm (the arm that goes between the diaphragm and the
breaker-plate) to allow for more movement and thus, vacuum advance.

Good luck,

John
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