Philippe,
The function of the vacuum advance is to advance the timing under light load
during cruise operation. Under full throttle, the vacuum goes away and the
vacuum advance is retarded, so only the mechanical advance is working. A
non-functioning VA will not affect full throttle acceleration. At partial
throttle, between full and cruise, the vacuum advance varies with the amount
of vacuum. Some loss of power will be noticed with a non-functioning VA.
During cruise operation, a significant loss of fuel economy will be noticed.
The VA should have no affect during starting, since there is little vacuum
during cranking.
If the VA leaks, it doesn't work and the vacuum line could be plugged with
no harm, and plugging would also prevent a vacuum leak. The short term
affect may be increased engine heat that could overload the radiator on a
hot day. The long term affect may be increased carbon deposits in the
combustion chamber.
Vacuum advance chambers are not repairable. New replacements are
occasionally found on eBay for around $10 to $25. The correct P/N for your
57 Imperial is 1689773, Autolite IAZ-2023RE, which is 22 degrees advance.
Close substitutes could be IAZ-2023RG (20 deg) and IAZ 2023RA (23 deg). A
spare is good to have around, since they are hard to find on short notice.
My parts book only goes to 58, so I have no P/N data on your friend's 59.
A non-functioning VA should not cause your friend's stalling, starting, or
missing problems. Since he has addressed most of the ignition and carb
potential problems already, he might try a fuel pump pressure check.
Dave Homstad
56 Dodge D500
-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of Philippe COURANT
Sent: Wednesday, May 22, 2002 4:17 PM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: [FWDLK] vacuum advance diaphragm leaking and other problems
Hi,
My Imp is ready to the 1000 miles trip (Chrysler Anciennes #2
meeting) but my friend ('59 Coronet) has some problem with his
car: no power, the car stalls at breakaway, very difficult or
impossible to start again, seems that engine misses some
cylinder(s) when it runs. He replaced points, condenser, coil
without results. He tried another carb (new), no results; he put
some gas in the carb and starting is always hard. He's checking
ignition wires and sparkplugs because it seems that it's a
ignition problem.
He found that the vacuum diaphragm is leaking (when he sucks or
blows, the air goes through). As he has no spare diaphragm what
could happens if he blocks the vacuum line from carb (to have no
vacuum leak). Could he drive the car without vacuum advance ?
--
Philippe COURANT (Pau, France)
Imperial 57 Crown convertible
Buick 58 Roadmaster sedan
- American Car Club de France (ACCF) : http://www.accf.com
- Chrysler Imperial France : http://www.ifrance.com/c-i-f
- Cadillac " Standard of Excellence " :
http://www.ifrance.com/accf-cad
- SportsCars : http://www.ifrance.com/accf-sprtcar
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