Vacuum routing for dizzy and carb

1930artdeco

1930artdeco

Well-known member
Ok, this week I hope to start hooking things up. What I am curious about because I cannot find it in the repair manual is the routing for the dist. vacuum line/source. I have a later valley cover with a PCV valve that goes to the back of the manifold (312 Y block). But where does the dist. Gets its vacuum from? I am Going to run a 1965 auto lite 4100 four barrel. I have what I think is a vacuum port on the side of the carb under the choke adjuster and I also have a spacer with a tube in it for a pcv valve that the carb sits on. Any ideas as where I plug the line into?

Thanks,

Mike
 
Going to run a 1965 auto lite 4100 four barrel. I have what I think is a vacuum port on the side of the carb under the choke adjuster ...
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That should be ported vacuum (vacuum source above throttle pates).

That is how the DUAL ADVANCE DIST is calibrated to work with.
 
1930artdeco said:
... But where does the dist. Gets its vacuum from? I am Going to run a 1965 auto lite 4100 four barrel. I have what I think is a vacuum port on the side of the carb under the choke adjuster ...
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This may be a similar carburetor(?) with the port for the distributor vacuum canister circled.
 

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Dmsfrr, bingo. I think the original 4100 was vacuum ported off of the fuel pump? But this carb has a port just where you circled. I assume it goes above the primary throttle plates or at least into one of the throttle bores.
 

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1930artdeco said:
Dmsfrr, bingo. I think the original 4100 was vacuum ported off of the fuel pump? ...
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The ported vacuum line between the carb and distributor is totally independent & separate from the manifold vacuum line setup that runs thru the booster on top of the fuel pump. That circuit goes back into the dash to run the wiper motor and a couple cabin heater valves, if equipped.
Those two different sets of vacuum lines shouldn't connect to each other at all.
 

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DMSFRR, ok I was at least in the ball park for vacuum. I am going to cap both ports on the pump as I have an electric wiper now and no other vacuum accessories. Other than the dizzy. But that will come off the carb and the PCV valve goes into the back of the manifold. Thank you very much.
 
The first of the Ford Y-blocks had a similar system to the flathead, which was the load-o-matic system, when they came out in 1954. The spark control was full vacuum operated against the adjusted spring tension of the distributor point plate. In 1956, the dual vacuum chamber distributor was used but may have been problematic since it was a one year only set up. The 1957 distributor finally had both a centrifugal weight set up and a vacuum set up so the carbs were changed from an all vacuum venturi source to a manifold pressure sensitive design so it could simply react to the lower manifold pressure under load or wide open throttle. The centrifugal set up did the initial advance according to rpm of the engine and flyweight spring tension. The vacuum portion could react to a sample of manifold pressure for load control.

A person just needs a carburetor for V8 models after the 1957 change. V8 carburetors used the centrifugal/vacuum system for many years after that and a lot of aftermarket carburetors have a port for that signal. Mixing and matching of load-o-matic components is problematic unless the carb is properly matched to the distributor.
 
OK, I saw a reply here I want to ask about. I have 3 Holley/Ford 94's on my car. The primary carb has choke plate, the screw in valve, and the idle passages. No vac port though. Right now my dist vac is picked up from a fitting in the intake. I have electric wipers. Can I use that vac port on my new carter fuel pump? How will that operate? I assume to do that I'd route that manifold vac line to the pump, through the pump, then to the dist?
 
The load-o-matic system it matched between carburetor and distributor and won't work on manifold pressure. An aftermarket distributor or a modified centrifugal/vacuum distributor for any V8 type that is easy to modify can be tailored to work on manifold pressure utilizing an adjustable vacuum can. The GM types are the most common ones chosen. This is more common on flathead V8s but will work for Y-blocks as well.
 
Anybody know where I can find the little nipple/adapter that goes into the carb? I cannot find one for the life of me. It is 3/8x24. All of the brass fittings I see are 1/8x27 in NPTF. NAPA didn't have anything either.
 
I have had good luck at Advance. My Advance store has them in the customer area, and behind the counter on a rack.
 
rotorwrench said:
The load-o-matic system it matched between carburetor and distributor and won't work on manifold pressure. An aftermarket distributor or a modified centrifugal/vacuum distributor for any V8 type that is easy to modify can be tailored to work on manifold pressure utilizing an adjustable vacuum can. The GM types are the most common ones chosen. This is more common on flathead V8s but will work for Y-blocks as well.
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Thanks Roto..., but I don't have a clue based on your reply. You experience in this area far exceedes mine.
 
Thanks, found a line that I am going to use at another auto parts store. Just need to figure the routing out as the coil sits right in the way:(
 
Ford used the same double compression fitting for many years . The Eaton number is 6100-3 but other companies made them under their own numbers.
 
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