I've got a ported vacuum switch located by the water outlet on the manifold, it has two outlets on it. anyone know what this is for? right now it's not connected to anything, should it be? 76 f150 360

 

Heated vacuum actuates the valve inside it,which allows warm vacuum to flow to the next part of the system

 

On some engines, the ported accum switch is where the distributor advance connect to. There are also several other components that goes to these depending on whether you still have the factory breather on it, etc. Like Dennis said, when it heats up, it allows opens the vaccumm to what ever componet is hooked to it. Some engines hav more that one ported vaccum switch....

 

Usually ported vacuum is connected to one of the ports on the "double" side. Manifold vacuum is connected to the other port on that side. The single port is connected to the distributor vacuum advance. Hook up the switch so that when the engine is cold full manifold vacuum is applied to the distributor. When the engine warms up ported vacuum is applied to the distributor. Some switches apply full vacuum if the engine overheats also.

 

actually that is backwards you want the distributor to get ported vacuum all the time except when running hot.the ported switch will give the distributor manifold vacuum at 210-220 degrees so the distributor will advance during high vacuum idleing and make the engine idle faster when its hot to spin the water pump faster and help cooling.
I think you want a "red" switch for this purpose.

allways run the distributor on ported vacuum unless you are running a heavy medium duty truck and you want a low vacuum retard for hill climbing.

 

Nope, -long experience here with these engines. You want full manifold vac when the engine is cold to give the A/F charge some extra time to burn. The A/F charge in a cold engine loses extra heat to the cylinder walls and does not build pressure as rapidly. I could always tell when the thermostat finally opened in those engines by the RPM drop.

Like I said, some vacuum switches had the "full vacuum when overheated" function but not all of them.

Otherwise the other information you gave was correct. I don't remember the switch colors but there were a number of them for function and temperature.

 

My factory manual describes the PVS function as Oldhalftons descibes it for air conditioner equipped trucks. Doesn't really matter though, you guys are describing a 3 port switch and the original quesiton was about a 2 port switch. If I was to guess it would be for some emissions function. Like engaging the EGR after the engine warms up.

 

where should the vacuum line on the distributor vacuum advance connect to? I've got a 76 f150 with a 360.

 

My OEM manual has a "cooler" PVS function described but it has nothing to do with AC. I just know how they work from working on many hundreds of these systems. I started as a mechanic in 1967 and had to work thru the nightmare years of vacuum controls before the cat converter and electronics. There are many of these switches used for a variety of functions. The most common one that is present on almost all engines is the one I listed. It is also one of the most common causes of poor engine performance reported by users.

The original user asked about a switch with "two outlets" saying nothing about the rest of the switch. I answered about the most common switch application. There is no way to know the exact function or configuration of his switch without more information. The user can also look up his vacuum diagram at Auto Zone if he has checked any of the other threads here.

 

It should be connected thru a PVS to both the full and ported vacuum sources.

 

ok, so the vacuum lines goes from the distributor to a pvs then where? i don't think mine is connected corectly. It goes straight from the dist to a conector on the carb but that conector is open and not conected to anything its just open.

 

There should be two ports near the base of the carb. One has full manifold vacuum, the other one has "ported" vacuum that has very little vacuum at idle but increases off idle. Both ports are connected to the PVS and then the PVS outlet is connected to the distributor. Check with AutoZone's website for a vacuum schematic. There are many other vacuum lines but you don't have to have them all to get your engine to run. To make it run right you do need many of them. To eliminate any of them you may have to make adjustments to the engine. There is no way to tell what you have until you go thru and check everything.

 

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