The dizzy i my 72 has to vaccume ports. What does the back one do. I had to unhook it when I put in a temp gauge. Do i need to hook it up somewhere?
Tha back one should be the vaccume advanced if im not mistaken. You are talking about the dist right? mine went to the intake manifold and pvs valve right by the thermostat housing.
It had a line going from the back of the manifold to the valve, that i removed, then to the the dist. If i suck on the line that goes to the front one, the dist advances. So what does the back one do?
One in back is vaccum advanced and the other sticking out is the retard vaccum. Vaccum advance and retard are options. Advance is nice if you want a little better mileage. Retard is only desireable if you are trying to meet an emissions test, otherwise it is undesireable. I dont use the retard vaccume. Not sure if others do on theirs.
The dual diapgragm keeps the distributor retarded unless the engine begins to get too warm - then the valve allows more advance at an idle to help cool the engine. If you removed the valve then you should not us the distributor port closest to the distributor - use only the port furthest from the distributor. It will further help to use manifold vacuum instead of ported vacuum - especially if the engine has a tendancy to over-heat at an idle.
That was fords' way of meeting emissions requirements. By placing better control on timing advancement. The engine will run just fine without the inner (retard) port connected. The feds may not like you. If you don't have any smog checks, your choice. If you leave that post on the dist unconnected, don't cap it as that will restrict the vac advance from working as well. RS
Sorry so long to reply. Thanks for the help. I'm just going to leave it unhooked. The car runs great and doesnt over heat. We will see this summer....
