Go back to to square one, put your timing light on it and start bring the RPM up and see if you are getting any advance at higher RPMs. If not it's probably the vacuum advance unit. Replace that if needed first and then recheck. If there is still no advance it could be something in the govenor, which I have no idea how that works.

 

It is very common for the vacuum diaphrams to dry out, crack and leak vacuum. The best way to test this is with a hand vacuum pump with the engine running and watching a timing light. I know you said you don't have a hand vacuum pump.

I would fully expect that the diaphram is shot, and it needs replacement. You may be able to find a replacement diaphram kit. Back in the day of points distributors and vacuum advance, it was a normal part of the tune up procedure to test the diaphram.

 

He did mention in the OP that as engine RPM increases advance does not.

So there's still the issue of mechanical advance. I think. Is "tach drive" a different name for a vacuum-only advance distributor, though? Load-o-matic was another.

 

Tach drive means it has a cable driven tachometer.. It appears his has no mechanical advance like a "load-of-crap" model, vacuum only.
OOPs I missed where he said it didn't advance with higher RPM..

 

Ah, OK... So the tach, while nice to have isn't a factor here in the advance mechanism problem. A '57 distributor should have a dual advance type distributor. He should be able to at least clean everything up and make sure the breaker plate slots, springs and weights aren't gummed up or seized. Vacuum advance can can be repaired as someone mentioned.

 

These large truck distributors are a totally different animal, nothing like a Y block. The vacuum units can't be repaired, they are a sealed unit, you just replace it..

 

If not a vacuum only unit though, should have centrifugal weights and springs? I dunno. You're right about that.

 

OP says when he sucked on the vacuum tube, nothing moved. Change the diaphragm

 

True that, but he's not getting any mechanical advance either, that's the killer.

 

As the original poster (OP) said here: https://www.ford-trucks.com/forums/1...l#post15090585

He has no mechanical advance to worry about...

 

Well OK.. Converting to a dual advance distributor would make sense if practicable.