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The vacuum advance is not working on my 1947 Deluxe Clipper. I can rotate the distributor by hand, but it is really stiff, and that is probably the problem. Is the advance mechanism's return spring the only resistance to it turning? Before I mess up what was probably a good adjustment, I thought I would ask the question.

Yes, the spring should be the only significant resistance. I assume you have the autolite system where the vac adv. turns the whole dist.

If it snaps back to position when you let it go then there is probably not a friction problem.

You can easily test your advance by hooking a bit of rubber tubing to the line at the carb end and sucking on it--it should hold a vacuum, and the dist. should move. If not, it's advance time which is hardly a surprise at this late date.

Thank you for the reply. I tested it with a hand vacuum pump and it did not hold vacuum or turn the distributor. I then removed the spring in the advance and found it was still difficult to turn the distributor. I think I am going to have the distributor and advance rebuilt.

I have a 1947 Super Clipper-I also had vac adv issues. I caution you on your test of the vac adv. I used a hand held vac pump(mityvac) to test the unit. It tested bad. When I got the new one and repeated the test it showed bad also-I believe it was leaking around the threads. Anyway the orginal vac adv was bad-the car would not idle-now it idles fine. I assume when you say move the distributor you mean the breaker plate in the distributor? I also got the new vac adv from Max Merritt other places will repair yours at for less $$

My whole distributor is supposed to rotate with vacuum, not just the plate. I can feel the vacuum at the line when it is disconnected, but I can't connect it to my vacuum gauge to measure the amount, because of of the fitting on the end of the pipe. I am convinced I need the advance unit.
With the vacuum line disconnected the car will idle at 400 rpm. and if I slowly rev up the engine I can see the timing advance, but because of the centrifugal advance. If I quickly rev up the engine there is a hesitation.
Rick at Hagen's Hiway Auto Parts says he rebuilds them to like new with modern diaphragm for $85.00
Jason Smith at Advanced Electrical Rebuilders says he has NOS units, but I didn't get the price yet.

Add Terrell Machine shop in Texas-he rebuilts them. Max Merritt probably has them on the shelf-but more expensive

I also have the distributor that moves the whole unit. It's a neat setup! Make sure that the two plates that hold it in the block are on right and a little lube, so it doesn't bind when you snug it down. A quick ID on the distributors is that the vacuum arm connects to a gauge with a pointer and a long slot on the outside of the dist body, while the plate moving ones just run inside a hole on the distributor body to connect to the plate.

Since there is no ported vacuum on our cars, the distributor will be very advanced when working well, at idle. A couple quick blips of the throttle and you will see it jumping around as it rotates. It's kind of neat to watch, and i like this model distributor very much for that purpose. While doing a ton of testing and tuning, i found mine had randomly stopped working as well one day. Got a new one from MM and it's been good since, although the car has a knock so it hasn't moved much.

I disconnected the vacuum line and made a video showing the timing being advanced by the centrifugal mechanism. I can't wait to see it with the vacuum advance working.
http://www.youtube.com/watch?v=P8fkIfD_rpk&feature=BFa&list=ULP8fkIfD_rpk