Folks,
I apologize in advance if this has been covered in another thread -- I looked and couldn't find it if it has. I have a '73 F-100 with 302, factory 2-barrel, no AC. The vacuum connection on the distributor is currently connected to manifold vacuum on my truck. I have never myself checked the vacuum "wiring" until now, and many, many shops have worked on this truck over the years I and my father have owned it. I understand there are many different vacuum diagrams for these trucks, but I think mine is connected improperly.

There is a single vacuum connection on the dashpot that is part of the distributor (vacuum spark advance), and right now it is connected to an intake manifold vacuum port. There is only one vacuum connection on the distributor dashpot and it is on the "front" of it. There is not one on the side. On vacuum spark advance units with two connections, the front one seems to go to the vacuum port on the carb (the one that reads zero at idle) and the side one goes to the intake (full vacuum at idle). I believe the one connection on mine should go to the carburetor port, and that is my first question: does it?

The only other thing connected to the intake manifold vacuum is one of the two steel lines that go out the rear of the engine compartment (to the transmission?). The vacuum port from the carb currently goes to the valve on the heater hose, and from there to a T that goes to the EGV and the other steel line running out the rear of the engine compartment. That is it. Should I put a T in the line from the carb port and connect the spark advance dashpot to it? And if so, before or after the valve on the heater hose?

Another thing that might complicate things is that I had the points and condenser replaced by a drop-in aftermarket electronic ignition module. Does this system still use vacuum to control the spark advance?

And finally, the engine is running mostly okay right now, but does choke off on deceleration, which is what got me looking at this. I have already cleaned the carb, checked the float, replaced the fuel filter, and adjusted the idle mixture, idle speed, and fast idle speed screws. If I do need to re-route the vacuum for the spark advance, what will be messed up?

Thank you.

 

It's been a few hours with no responses. Have ya tried Googling for a diagram? There seem to be quite a few available online.

 

I have looked, and found many for related models. There seems to be wide variation. I was hoping someone would know as as general principal, if the single-connection vacuum advance went to the carb port or the intake manifold on that engine.

 

my 74 f100 302