vacuum unit broken on dizzy of a 1982 911 SC 3.0

[BasRottier]

Hi,

I have a 1982 SC 3.0 that was imported from Florida to Holland (now in Belgium).
Unfortunately, the dizzy is damaged. it is the vacuumbox (Porsche ref 93060293300 or Bosch ref 1 237 122 763) which is EOL, but it isn't available in the aftermarket either.
(it has connections for 2 hoses)
Would anybody know if it can be replaced with a compatible one? (one that would still respect the timing of the ignition)
Or should I go for full electronic ? Any suggestions?

Thanks in advance,
Bas

[Jonny H]

All the vacuum unit does is give another 5 degrees of advance at light throttle load when cruising. This is in the vain hope of improved fuel economy. As soon as you touch the throttle it has no effect.

Unless you are doing long distance cruising barely touching the 'go' pedal, I wouldn't worry about it.

[Flat6pac]

The double vacuum unit has retard and advance.
The retard side, closest to the distributor, is used for meeting emission at idle. The vacuum source is below the throttle butterfly.
The advance is moved forward as the RPMs increase. First mechanically, then with vacuum from demand of the motor for more air. The hose for vacuum originates above the butterfly.
The advance isn't totally in until high RPMS
Bruce

[BasRottier]

thanks,
But my car has a behaviour that is quite 'shaky' between idle and let's say 3000 RPM. Specialists tell me the Dizzy is OK, but the vacuum part is causing this behaviour. It is no pleasure driving.

[Flat6pac]

Start the motor and take the hose off the pod.
Touch it to your tongue. Is there a vacuum?
If there is, you're on the wrong port to the throttle body
Considering the pod doesn't kick in until high RPMs you shouldn't be having problems at low RPMs
Pull the dist. And remove the pod, you should have rotation in the distributor of about 30-40 degrees.
Bruce

[Dave Kost]

Put a timing light on to check if the distributor rotor advances smoothly. If the timing mark jumps around - there is your issue. ( Usually what happens is the spider ring is frozen and won't move- so the vacuum pod won't work.)

Then I would pull the ignition distributor and inspect it. ( I would do this anyways)
Any end play on the shaft?
Runout of the shaft?
Is the spider gear advancing smoothly?

If any of the first two items are a concern, the distributor needs rebuilt. If Not, then I would buy a gallon of your favorite penetrating oil and submerge the distributor for a few days, occasionally blowing it out with compressed air- watch all the crap that comes out!