I have a 2.2L 911 engine with carbs that I believe has a poor distributor advance curve. As you can see from the picture below the vacuum advance mechanism is locked down with a screw.

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If the distributor was designed to have a vacuum advance then wouldn’t the springs and weights be set up for this? If I set the distributor to get about 30 degrees of advance at 5000 RPM then at about 1000 RPM I am sitting at around 10-15 degrees when I think it should be at 5 degrees.

Looking for some advice on this or help on where I should go to get help with this.

Jeff B

I can't fully remember but are you sure that vacuum can isn't a retard for timing ,take the screw out and test it,the advance plate will work in the opposite direction if so.
Your mechanical advance must be working as you wouldn't get your indicated 30degrees advance.
Bosch distributors with end numbers 004,005,008,and 009 had this retard system ,I notice most folks seem to remove them when they fail.
What year is your motor because I was thinking it would have a Marrelli distributor being a 2.2,the original setting for that was 35 degrees @ 6000rpm so if yours is converted to a Bosch it would be the same.
If you can remove the points plate and check the advance weights are moving fully,they can gum up over the years and not advance fully...give them a good clean and lightly lube them,also remove the felt oil wick from the shaft under your rotor and clean down in there,replace the wick and put a few drops of motor oil into the felt.
I also highly recommend you convert to a pertronix ignitor ll module and matching coil,my 2.2 runs really nice with this setup.
Good luck.