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Can anyone explain how this vacuum port works? The spring clip opens the little ball joint when depressed. I tried blowing in the small holes and can’t perceive any air movement
I believe that it's a simple open/close valve that's thermostatically controlled (the bi-metallic spring thingy) that is sensing the temperature of the incoming air. Once it reaches a certain temperature it either opens or closes to start of stop the vacuum signal.
If I remember (which I might not!) it's for controlling the hot air riser diverter part of the air cleaner snorkel. Which either allows colder outside air in when up to temp, or allows heated air from the exhaust manifold in when it's cold.
At least that sounds like a good story I just made up on the spot!
I'm sure someone will chime in with corrections if I'm mistaken.
Didn’t consider the bimetallic spring. Must be closed when cold, thus pulling warm air from that manifold divert tube and once warmed up, open to allow vacuum to open the fresh air diagram on the air cleaner snorkel
My air filter lid has 1 hose that runs from the lid to the snorkel. Does it matter which nipple it is on? The other nipple does not have a hose on it. When I place a hose on it, we're should the other end go?
Does it matter which nipple it is on?
When I place a hose on it, we're should the other end go?
I do not believe it matters which nipple each hose is on, but I believe Ford set it up so that the fitting closest to the snorkel was used for the flapper valve and the fitting furthest away went to vacuum.
As to where the vacuum is connected, it’s probably a can-o-worms. Might depend on which year you have, but more than likely the vacuum is not sourced directly from the intake manifold but instead goes to one of those thermostatically controlled vacuum valves. Do you have any of those remaining on the engine?
And just as important, in case it’s shown there, do you have any remaining vacuum routing decals on the underside of your hood?
Someone out there probably has either a diagram, or an existing set up that still stock. Might even be me!
i’ll see if I can get a picture of mine later.
I do not believe it matters which nipple each hose is on, but I believe Ford set it up so that the fitting closest to the snorkel was used for the flapper valve and the fitting furthest away went to vacuum.
As to where the vacuum is connected, it’s probably a can-o-worms. Might depend on which year you have, but more than likely the vacuum is not sourced directly from the intake manifold but instead goes to one of those thermostatically controlled vacuum valves. Do you have any of those remaining on the engine?
And just as important, in case it’s shown there, do you have any remaining vacuum routing decals on the underside of your hood?
i have a thermostatic switch on the water neck, but someone cut all 3 lines going to this switch. Other nipple to vacuum makes more sense at there needs to be vacuum to pull that back valve open.
This is the vac disgram for a 79 f350 400 automatic. It is typical for preheater/heat riser setups. There are two vac switching valves and 2 delay valves. One cuts off vac below a certain coolant temp, one below a certain air temp and the delay valves slow the application.
Thanks for the diagram aldridgec. I have a pic of mine saved somewhere, but I lose that stuff regularly anymore! Glad yours is more easy to hand.
It shows that for the diverter valve at least, there is only one little thingy that egchewy needs to worry about for this circuit.
You can see that the vacuum source is straight from the vacuum tree at the back of the intake manifold. No temperature control as of yet.
From there it goes to one side of the air-cleaner bi-metallic valve (A/CL BI MET on the diagram) and from the second nipple to a color coded VRDV whatever that stands for. From the VRDV direct to the the air-cleaner diverter (A/CL DV) on the snorkel.
So only the VRDV is controlling vacuum timing here. Easy peasy... Once you determine what color/rating the unit is. By a book or by someone's stock setup.
So we should take a poll on who knows/guesses the actual meaning of the letters. Unless someone has the book handy. Vacuum Reducing Delay Valve maybe? Seems reasonable...
Do you happen to have one of those things laying around in your pile of leftover parts egchewy?
The VRDV is plastic and the cap color inside air cleaner side. I have saw white and blue paint daubs on the bi metalic sensor. Figured they meant different temp ranges. Back in the day of emission testing of carbed Mustangs think the blue cap VRDV from a Pinto was the hot ticket. Sad thing is all this stuff actually worked in the day, but most were thrown away or disconnected. Low compression and retarded camshaft was a grasping a last straw era and air injection was a pitiful attempt to cover epa requirements. Some of the HD trucks had 2 air pumps, blow enough clean air out the tail pipe and everyone is ok. This generation is left trying to figure out the mess.
Thanks for the diagram aldridgec. I have a pic of mine saved somewhere, but I lose that stuff regularly anymore! Glad yours is more easy to hand.
It shows that for the diverter valve at least, there is only one little thingy that egchewy needs to worry about for this circuit.
You can see that the vacuum source is straight from the vacuum tree at the back of the intake manifold. No temperature control as of yet.
From there it goes to one side of the air-cleaner bi-metallic valve (A/CL BI MET on the diagram) and from the second nipple to a color coded VRDV whatever that stands for. From the VRDV direct to the the air-cleaner diverter (A/CL DV) on the snorkel.
So only the VRDV is controlling vacuum timing here. Easy peasy... Once you determine what color/rating the unit is. By a book or by someone's stock setup.
So we should take a poll on who knows/guesses the actual meaning of the letters. Unless someone has the book handy. Vacuum Reducing Delay Valve maybe? Seems reasonable...
Do you happen to have one of those things laying around in your pile of leftover parts egchewy?
Paul
i do have a plastic do-hickey in line between the nipple on the air cleaner and the snorkel. So from my understanding, there should be another vacuum line going from the back of the carb directly to the other nipple, right?
Not the back of the carb. The "back" of the intake manifold. They're called vacuum trees, although some are just multi-port manifolds while others actually look like a tree (my '79 has a "tree" type.
But you're looking for an available port on the intake according to that diagram.
Sometimes they used a T-fitting to let the vacuum go to multiple places, but at least as far as the diagram is concerned, there wasn't a T needed in that particular circuit. A T or not though, the function is the same for getting full manifold vacuum to that valve on the air cleaner.
