74 fleetwood vacuum advance not working

[ithaca1230]

Spent a couple hours with the mechanic yesterday changing the points and trying to get the old girl tuned up and running correctly. One thing that we found was the Vacuum advance on the distributor was not working. What do you guys recommend. Is this part replaceable or should we replace the whole distributor. While we were there we replaced most of the old vacuum lines that were dried up. Car runs good with all new wires plugs cap rotor.
Thanks
Billy Epthimiatos

[30326]

Would say you should be better off changing to an electronic ignition and a new coil http://www.pertronix.com/default.aspx.

Here is a way to do it on a car that is 10 years older than yours: http://6364cadillac.ning.com/forum/topics/pertronix-ignitor-ii-and-flame-thrower-ii-installation

Now I have to admit I am not sure how the -74 distributor is designed. But normally its very easy to replace the vacuum advance and cost of a new one is low. Use a vacuum pump if the screws are hard to get too.

[ithaca1230]

Hey thanks! I will do some reading on this and see if it is something I can do myself.

["Cadillac Kid" Greg Surfas 15364]

Billy,
The Vacuum advance is a replaceable part.  They are essentially exposed to gasoline vapor (via the vacuum connections) and have a limited lifetime.  Replacement is a very common task.
Even if you convert to another type of ignition you will still need a vacuum advance for temperature control, fuel economy and idle stability.
Greg Surfas

[Scot Minesinger]

I have three 1970 Cadillacs, two with electronic ignition conversion, the other with points and condenser, and while the conversion made absolutely no difference in performance or anything, the one remaining points and condenser Cadillac is the best running of the three.

BTW as Greg wrote that vacuum actuator is replaceable, and easily done.  The part is readily available.  Electronic ignition was an option in 1974 (first year).

[ithaca1230]

I would like to order order a new vacuume advance but I'm having trouble sourcing one any suggestions.
Thanks

Billy

[Jeff Rose CLC #28373]

While it more than likely needs to be replaced, it may just be frozen if it sat long. Hook a vac hose up to it and suck. If it holds vac then it may be good. If it like suckling thru a skinny straw (think coffee stirrer) then the diaphram is bad and needs replacing. If it is good then try to get it all moving in the distributor and lubricate. Don't get any lube on/around the points. However be prepared to replace it.
Jeff

[TJ Hopland]

What usually causes you to have to replace the whole distributor is wear in the bushings or shaft.   An indicator of the condition is how steady the dwell reading is.   A badly worn distributor the dwell will tend to jump around especially as the rpms change.   A solid distributor the reading will remain steady.   Sometimes the weights and such can have issues but that didn't seem to be a problem with the points style, more common on the later HEI. 

Replacement vacuum canisters these days seem to be a one size kinda fits most sort of thing so looking for a 'performance' model that is adjustable as far as the amount of travel may be best so you can try and duplicate the original specs.   There should be several options.   I believe the top of the GM V8 distributors was pretty standard from the late 50's early 60's till the end.   It was the bottom that was different to fit different engines and then the 'tune' that varied.

[ithaca1230]

I would like to replace it just can not find one I am sure will fit the car.

[30326]

This should work. Took 2 mins search online for it:

https://www.summitracing.com/int/parts/acc-31034/overview/year/1974/make/cadillac/model/fleetwood

[35-709]

Be sure to set that adjustable vacuum advance up with a tachometer and timing light according to the specs in your Cadillac factory shop manual or you may well have moderate to severe pinging like another poster here recently wrote about.  It should go without saying that ours are not SBC Chevy engines and do not respond well to the kind of aggressive advance a Chevy will. 

[TMoore - NTCLC]

...or, if you decide to replace the distributor -

http://www.rockauto.com/en/catalog/cadillac,1974,fleetwood,7.7l+472cid+v8,1026526,ignition,distributor,7108

[James Landi]

Is the '74 vacuum advanced hooked up to a vacuum break that does not engaged unless the car is up to speed (my '70 and '72 had the arrangement)?  IMHO-- taking the advance and running the vacuum directly to the manifold gives these model cars a much more response engine response (i.e. taking the vacuum break out of the circuit).  James Landi

[TJ Hopland]

73 they got rid of that speed limit vacuum solenoid dodad.   The second part of that was a little gearbox thing hanging off the side of the transmission with the speedometer attached to it.    74 Likely just had the thermal vacuum switch kinda near where the distributor goes into the block that changed between ported (carb) vac and manifold vac depending on coolant temps.    Those switches often don't seem to be working properly at this age.   I have seen them stuck and plugged up not passing any vacuum as well as having vacuum on all 3 ports at the same time.  Never took one apart to see how that is even possible.