This original set up is in a 1956 Merc 312 Thanks for the information. AR

As always, thanks for the insight!

If you’re looking for a timed or ported vacuum source for the distributor, then this will need to come off of the carburetor.  Timed or ported vacuum will originate at a point just above the throttle blades when the throttle blades are in the idle position.  Starting in 1957, all V8 Fords had a timed port at the carburetor specifically for distributor vacuum advance control.  Prior to that, it was a combination of timed and venturi vacuum being regulated by a spark advance valve located on the carburetor.

Any vacuum ports that are sourced below the throttle blades will be direct vacuum.  If attempting to use one of these for distributor vacuum, then read some of the past posts on how to time the vehicle accordingly.

Here are some past threads discussing both direct and timed (ported) vacuum uses at the distributor.

http://www.y-blocksforever.com/forums/Topic44648-3-1.aspx

http://www.y-blocksforever.com/forums/Topic49569-3-2.aspx

http://www.y-blocksforever.com/forums/Topic57850-3-2.aspx

http://www.y-blocksforever.com/forums/Topic11631-3-1.aspx

Using the search function will bring up more.

Basically, I may want to eventually change out my carb to a later model.  I knew to do that I would also need to change the distributor.  What I hadn't realized though was that changing the distributor also meant making modifications to my intake manifold.

I'm kind of a purist, but my carb continues to give me headaches even after a rebuild last year.  Right now, everything is as she left the line back in '55.

I thought my stock 272 just had the carb vacuum line going to the distributor, but after reading last night does it also have one coming from the manifold?  I'd check but right now she's under a cover.  So if it's just the carb vac line, sounds like I'd have to tap a hole as mentioned.  May be a good time to go to a multi-carb set-up.  Any suggestions on where I might look to for a new manifold with the requisite vacuum ports for a '57-'64 distributor?

Also, are there any other distributor choices beyond the original Loadmatic and '57+ options that would not reqiure a vac line from the manifold?  Again, that may be a dumb question.

Just an FYI....I have a lot of trouble with the search function here   I can't seem to go to the next page when the search results fall over to more than one page because it says I can't search within 15 seconds even when it's been minutes, etc.  But either way, I really appreciate the help you guys give, and will certainly continue to try and utlize search.

Any ’57 and later distributor can be run without the vacuum line hooked up to the distributor.  In this mode, it will be relying solely on the mechanical advance portion of the distributor.  Some recurving of the ‘’57 and up distributor can have the driving attributes the same with only the mechanical advance portion versus using both the factory mechanical and vacuum portions working together.

If you are still using a pre-1957 carburetor but have a ’57 or later distributor, then you need to modify the carburetor so it has a ‘true’ timed or ported vacuum port if wanting to used the vacuum can on the distributor.  A recurved ’57 and up distributor being used without the vacuum at the distributor for the short haul but using the vacuum signal from an unmodified pre ’57 carburetor will supply too much vacuum for the ’57 and up distributor vacuum can when used in conjunction with the mechanical advance.

Assuming you have the three bolt 2V carb, check out this link for the necessary modifications.

http://www.eatonbalancing.com/blog/2010/02/07/modifying-the-holley-94-two-barrel-for-late-model-distributors/

There’s a modification that can be performed on the Teapot 4V carburetors that also accomplishes the same thing.

I also probably need to slow myself down a bit.  I want to dive right into making a bunch of changes in order to solve a nasty tip in hesitation issue but would likely be better served by taking things on one at a time, as originally planned.  You know how it goes though....car is out of storage and the euphoria is hitting me!

Anyway, I was going through the service manual while under the hood last night.  Yes, I have the 2v Teapot Holley, which is connected above the throttle body into the vacuum advance unit.

I probably should start another thread about this at this point, but I really hate clutter, so I'll just throw this out here now and go from there:

The issue is tip in hesitation.  Additionally, it seemed to me late last summer that on really hot days, when at idle the engine would (this is hard to explain) rev up and down a bit.  When going to a stop sign, the reving down part of the cycle would almost (sometimes would) stall the car.  These two things may be totally unrelated, as I understand that this last issue may be gas boiling in the fuel line to the carb, maybe. 

Rebuilt the Holley last year, which included of course installing a new power valve.  There was a lot of crud in the bowl at the time and it seemed as if the tip-in hesitation went away for a couple of weeks, but then came back.  It had new plugs and wires installed when I got the car last April.

So my plan now is to work my way up from the gas tank system by system, because I'm not sure if there could be more than one variable at work here.  Have an in-line fuel filter on backorder.  Once that is installed I should see whether the tank needs replacing.

If not, I'm moving back to the carb and will replace the power valve again.

Finally, is there a way to test the vacuum advance unit?  I'd simply replace, but at $62, if there's a way to test first I'd prefer that.

After that, it sounds as if the hesitation may simply be a driving characteristic of the loadamatic set-up (?).  If so, I'll have to weigh changing the carb/distributer combination.

Does this sound like a good 'battle plan'?

Sorry....I can get wordy. 

The old style carb and Load-O-Matic distributor isn't a favorite amoungst Y-block enthusiasts - but the fact is - it can and will work for well maintained vehicles brought to near original condition. There are wizards on this board that can get it to work and work well.  The "trouble" is in the maintenance of the system (by we mortals) - and performance can quickly slip.

The later distributor offers some serious advantages - both in tuning and consistent, reliable performance. I would suggest that you get a base gasket for the 2V carb (an intake manifold gasket) and go looking for a way to put a small (say 1/2 inch) spacer under the carb. Some artful drilling and a small piece of brake line tubing will allow construction of an attachment port that is sampling vacuum from under both venturis. This will provide the necessary signal to use the later distributor with your carb - I've seen this sort of spacer made out of marine plywood and it worked well.

I love all the info I'm learning!

I'd still suggest you look into a rebuilt distributor from a local source - and asking for the one for the '64 -292 truck engine is your best option by far. If you use a spacer to get your manifold vacuum source - the distributor will work with a more modern four barrel arrangement should you want to try one, one day.