Thought I would post the following - hopefully it will help someone.
Note - as far as I can tell from a Chilton's reference, the attached diagram seems to work for any 78-79 300 CID. If not, it's real close. Couple of real-world changes:
A) On mine there is only one (1) line to the vacuum canister. This shows 2.
B) This shows one line to the PCV. Every pic I have been able to find for a '78 PCV shows 2 lines.
1) Purge CV - is the gang valve on top of the carbon canister, on my truck just behind the right front radiator support.
2) I have a vented fuel tank - a short hose connects it to a long metal line the length of the truck, to the line showed from the carbon canister.
3) V REST is an inline round plastic thingy in the hose. 3 is the PCB, mounted in a grommet onto the rear half of the valve cover. Per note B above - I ran the second line to manifold vacuum.
4) - Is the air cleaner diverter valve, located on top of the horn of the air cleaner. It's the only connection on top of the air cleaner.
5) The Bi-metallic switch is a small valve with two connections located in the BOTTOM of the air cleaner.
6) INT MAN is the intake manifold- there is a vacuum "tree" screwed into the intake just below the carb base plate. There are additional non-emissions vacuum lines attached to it, for the transmission and power brakes (if equipped.) Mine has 5 branches.
7) The Vacuum Reserve is the tin-can vacuum reservoir located on the driver's fender near the hood hinge. As in note A, mine has only one vacuum line but has a round T-connecter/valve in it, one line of which heads into the dash presumably to the AC/heat controls.
8) VRDV is one of those round in-line plastic parts (colors may vary)
9) The TVS, Thermal Vacuum Switch, located in the rear of the air cleaner and has a push-on connector with two different-diameter lines on it.
10) The S (Spark) port is where your vacuum advance hooks to. On my Carter YFA carb that is the only port in the carb baseplate and is by the idle adjustment screw.
11) The E port is in the YFA mid-section just above and to the rear of the S port. On mine it is pretty much concealed by the bracket for the throttle positioner bolted onto the rear of the carb.
12) WOT is a Wide Open Throttle valve - I have seen pics of it and it looks to be a round valve about 1" in diameter and 2" long mounted at the front bottom of my carburetor. Mine is long gone (if ever was).
13) BV is Bowl Vent - on mine right by the fuel inlet. Not shown on the diagram but on mine is a round in-line plastic restrictor valve.
14) This is the small port on the EGR valve.
15) is the vacuum advance on the distributor.
16) Not shown) - there is an additional 1/4' vent on top of the carb, which faces the right fender - it is the clean air line for the choke assembly.

 

Excellent resource! I've had to use these on the old EFI 5.0 Mustangs.
But fortunately, my truck is an F150 with apparently a '69 240, so I think my only vacuum lines are to my distributor advance and PCV.

 

i have the chiltons and i used this but i dont have a TVS VCV or smog pump so i had to improvise and connect things where it made sence, runs great but bogs at mid throttle.

 

My smog pump sits in a box. Other posters have told me that the only things you really need are the vacuum lines to the AT and power brakes (if equipped), vacuum advance, and PCV. You can probably cap everything else. The mid-range bog -think I would just go through the tune-up basics of plugs, timing, checking for leaks, etc. initially.

 

life saver just changed head gasket and even though i marked everything a few pieces of tape came off.

 

Where is the ported vacuum switch? Its the sensor on the thermostat housing.

Is the EGR connected to the "vacuum tree" ?

Thanks MIKE

 

On mine the EGR is T-ed into the hose that runs from the top of the purge valve on top of the vacuum canister to the thermal vacuum switch by the thermostat. Not sure I understand the other question - the main ported vacuum connections are on the carburetor (like the S port for vacuum advance), there is no 'switch' for them. Maybe someone who understands this better than I can answer?

 

Excuse me friends, I have a 1977 4 door ford maverick and have a 6 in line cylinder engine known as the 250 and the carburetor is a carter yf/yfa, was working well until a big trailer crashed against my car, and caused a fire, very much of the cables and a hoses were destroyed by the fire, I have worked on it for 2 years and almost is working again, I have found some missing hoses and if you may tell me where it is connected the hose that goes from the distributor vacuum canister to the carter yf/yfa carburetor will be great, today the engine starts and run, but if I select the "Drive"shift, the engine begin to work very irregular and stops, I am thinking is that hose, may somebody help me? , Thanks in Advance, Octavio Salcido

 

Reviving this thread. Thank you HoustonDave for the detailed explanation.it is really helpful for those is us with these rare birds. Particularly in smog check states. I have this motor with CA emissions. I believe one correction is needed. I think Number 9 is the thermal vacuum switch located on the front of the motor. I believe it is connected to ported vacuum on the YFA (upper right pass). The TVS only allows vacuum to the EGR when the motor is warm and the vehicle is under acceleration or cruising. It should close vacuum to the EGR when cold. Mine is like this one with only two ports. One is vacuum in and the other (bottom I think) is vacuum out to EGR. Mine works this way but exact info is really hard to find. Thought I’d try to contribute here. Thanks again.

 

you are correct... not sure how I messed that up. Moot point on mine now, I live in a free state and when I changed manifolds and carbs, all the emissions hoses sorta fell off. Carbon cannister and PCV are what's left, along with lines to the heater controls, brakes, and trannie.