I'm looking for pictures of where vacuum lines go on a 1979 300 CID. Specifacilly the 3 lines from the charcoal canister, and the two lines form the vacuum control valve up by the water thermostst. Also the air cleaner/filter lines, and the two lines from the PCV on back of the valve cover. All others if you got em. If you don't have pictures, try and explaining it to me.

Thanks in advance

 

cant seem to get the pictures to work on here, Ill post them in my gallery

 

IKE, MY 300 SIX IS A LITTLE DIFFERENT THAT THIS. First off my charcoal canister has 4 ports. Anyway thanks for the effort. Someone out there must have a 1979 300 inline six.

 

Sgt,

I have a '79 300. Unfortunately, when I replaced the inner fenders, I pitched the charcoal canister with it. I can't tell you which ports on the canister go to what, but I can tell you in general terms. One port is for the metal line that goes all the way to the fuel tank. A small length of rubber hose connects the end of the metal line to the canister. This line is for evaporative fumes from the tank. Another one of the lines goes up to the air horn of the carburetor (at the very top). This is where fumes are purged, for reburning. A third port is for ported vacuum. It is usually tapped off the EGR vacuum line. It is sourced after the ported vacuum switch (more on that later). The vacuum is used to purge the fumes in the canister into the carburetor. If you have a fourth port on the canister, it may be the fuel bowl vent valve which would run up to the carburetor. This is for fumes that evaporate in the fuel bowl inside the carburetor.

As for the ported vacuum switch - this is the valve that is next to the termostat. It opens\closes based on coolant temperature. It has two ports. One port connects to ported vacuum on the carburetor. It does not matter which port on the switch you use. Ported vacuum on the carburetor is above the throttle plates - it has zero vacuum at idle, and has vacuum when you open the throttle. Make sure you're running ported vacuum to the switch and not manifold vacuum, otherwise your EGR valve will be on at idle and your truck will stall. The other port on the ported vacuum switch runs to your EGR valve. This supplies the EGR valve with ported vacuum only above a certain temperature. You can tee off this line for your canister purge vacuum signal. That is how the factory did it for these trucks.

For your air cleaner - you should have one vacuum line starting from manifold vacuum. This can be from the very bottom of the carburetor, or from the vacuum tree on the back of the manifold (lots of available vacuum ports there). This line runs up to the bimetallic temperature switch on the air cleaner. Similar to the ported vacuum switch, this switch opens\closes based on temperature, except it uses ambient temperature instead of water temperature. Again, it does not matter which side of this switch you run the manifold vacuum to. You then connect the other side of this switch to the vacuum motor on the snorkel of the air cleaner. This vacuum motor (basically just a diaphragm with a rod) opens\closes a small door on the air cleaner snorkel so that the carburetor can draw in warm air wafted from the exhaust manifold during cold-starts rather than fresh air, which in some climates can ice up the carburetor. On some systems, there may be a check valve inline with one of the vacuum lines on this setup.

For the PCV valve - the PCV valve sits in the back of the valve cover. You want to run one 3/8" vacuum line from the PCV valve, to manifold vacuum. You can find a spot for this possibly in the vacuum tree, or you may have a port for it on your EGR spacer plate. That's one half of the system. For the other half, you should have a hose fitting in the front of your valve cover. Run a hose from there, up to the side of the air cleaner - it attaches to a breather filter. The system is: manifold vacuum, pulls through the PCV valve, pulls through the crankcase through the valve cover, pulls through the other PCV hose, which pulls in fresh air through the breather filter in the air cleaner.

I think I got it all covered - I couldn't help you specifically with which port does what on the canister, but that's what the ports do in whatever order. I covered the ported vacuum switch, the air cleaner lines, and the PCV lines. Let me know if you need anything cleared up.

 

Thanks Jeff, you have helped immensely. But I would still like to know which line goes where on the casister. I have connected the fuel tank line and the one that goes to the air horn on the carberator. The other two I know where they go, but which one goes to what? The three smaller lines seem to be in a triangular cluster (one being on top and the other two on the bottom, with another on the side.