Just wondering if sucking on the vacuum advance hose would be enough to test the diaphragm or if I need a vacuum pump?  (4k distributor) I'm not getting any movement. 

Thanks. 

Sucking is plenty.

Can you turn the base-plate by hand??

If it doesn't move around freely & smoothly take it out and lube the rusty ball bearings it sits on.

Unless the vac diaphram has really died...

2 hours ago, altezzaclub said:

Can you turn the base-plate by hand??

If it doesn't move around freely & smoothly take it out and lube the rusty ball bearings it sits on.

Unless the vac diaphram has really died...

I know with mine I could tell the plate mechanism was seized by feeling it, but sucking on the diaphragm it was clear it wasn't punctured because it was like sucking on a blocked straw, i.e. no air getting through. 

Seems like the previous owner had gone 20 years without oiling the vacuum or mechanical advance mechanisms--I bet that would be common, being hidden under the points, etc.! A couple of drops of oil and some wiggling back and forth and they were perfect again

Thanks. I'll have a play with it tonight. 

I had a play and it's definatley not working so I swapped it with a ratty one from another distributor I have. Also doesn't work. I've been giving the engine a birthday to try and get rid of the vacuum leaks. It seems to be never ending. Redid the manifold gasket, big improvement. Replaced the vacuum hoses, huge improvement. Almost there but still not happy which is why I was looking at the vacuum advance. 

Is it possible to buy a new vacuum advance without buying a new distributor, or can they be repaired?

Thanks 

 

So, if you suck on just the diaphram units neither of them move the arm in??  Do they leak air through into your mouth?

Does the base plate turn easily with your thumb?

They are swaged over so wouldn't be repairable, but I expect you can by a new one from some distributor tuning specialist.