The different fuel lines have been sorted out and the remainder of this post is going to be adding the components needed to create an EEC system. The below diagram is just a basic showing the components that are needed for a functional system. The one exception in the diagram is the carburetor fuel bowl vent tube, some carburetors have them some don’t and it’s not absolutely necessary and not all charcoal canisters have a tube fitting for this line, it could be (T) in to the vent line from the fuel tank. I found on older systems that if the carburetor vent is not used or not there it might cause a slight smell in the garage around the carb but not bad.
The first item you’re going to need to make an incorporate in your EEC system is what I call a high loop. The different car/truck manufactures call it by different names, but all of them do the same thing. They prevent gas in a liquid form from getting to the charcoal canister, the canister cannot handle liquid gas and it would just run out the bottom of it (not a good thing to happen).
The high loop is easy to make and cheap, I made mine out of 3/8 aluminum tube but finding the place to install it can be the hard part, you’re going to have to figure this out for your particular truck. The top of the loop needs to be approximately 10 inches above the top of the fuel tank or higher. I would not make it out of a smaller tube because liquid fuel could be forced over the top of the loop and not drain back into the fuel tank. I also would not make the high loop with fuel hose because it could become kinked/compressed blocking the vent system.
The 2 EEC lines on Chip’s tank can be (T) together and then to the one end of the high loop, the other end of the high loop is to the line running forward to the charcoal canister.
There is another option that Chip could use to create a high loop if he wants to locate a Liquid Check Valve that can be seen in an earlier picture in this post (Blazer and Jeep Vent). The Liquid Chick Valve needs to be located approximately 10 inches above the top of the fuel tank. Of course finding and buying one might be higher in cost than a simple high loop but it might be easier to locate it on the truck.
Next you need to run a 3/8 vent line from the high loop to the engine compartment. Normally the factory cars/trucks run this line inside the frame and parallel to the fuel feed line. I try to use as much fuel tube as possible minimizing the use of fuel hose, I feel it’s safer to do with tube instead of hose. This is how I ran mine, ref post #311
http://67-72chevytrucks.com/vboard/s...318544&page=13 .
In the vent hose just prior to the charcoal canister there needs to be an Orifice/Restrictor, in the factory installation you probably would not be able to see it or even know that it was there. Finding one or buying one is almost impossible, but making one is simple. When using a 3/8 vent hose at the charcoal canister you need to obtain a peace of aluminum or steel rod 3/8 inch in DIA. by ½ inch long and drill a 1/16 DIA. hole thru the center of it. Insert this Orifice/Restrictor in the vent hose, it doesn’t need a clamp to hold it in place. The picture below shows the Orifice/Restrictor on a factory installation.
The factory Charcoal Canister on an EEC systems for the 71 – 72 trucks can be found to the right of the battery. If you can find a canister mounting bracket (grate), if not you’re going to have to make one. The location to the right of the battery or there about appears to be a good location to install one.
Finding a Charcoal Canister for this modification. Finding a used canister for the 71 – 72 trucks is probably impossible and if you do find one it’s probably not functional (cracked, broken, clogged filtering, or inoperative Purge Valve), they do wear out just over time. I did a quick look over the internet (as of this post) and found no replacement canisters being listed or obtainable for the 71 – 72 trucks. (Not is all lost ---- smile) Over many years since EEC systems have been used the charcoal canister has changed very little and their function is basically the same. You can find many different sizes small – large with more than one purge valve on the top and multiple in and out vent lines. I would recommend finding and using one with just one purge valve on top and one in line for the fuel tank vent line and a size similar to the ones used on our trucks (4-1/2 inches DIA X 6 inches tall). No need in trying to figure out what additional lines to cap off or fitting a larger canister.
Here are some pictures of a canister that I found at NAPA that will meet the requirements, it is listed for many different GM cars/trucks from 1973 to 1980. As of this post the canister NAPA part number is CBR 229817 and the approximate cost is about $100.00 dollars. I’m not trying to say that this is the only one you can use and by this manufacture, I’m just using it as an example of what can be found.
The hose size can be different on different canisters and you will need to check their fitting sizes on the one that you’re using. Reference back to the basic EEC system picture to see how to hook up the lines from the canister to the engine.
1 (Top line on purge valve) goes to a timed vacuum port (at idle it has no vacuum, above idle it has vacuum). This one could also be (T) into the distributor vacuum line.
2 (Bottom line on purge valve) is connected to the PCV valve hose, see below picture for options.
As I said earlier in this post you may have or not have the carburetor fuel bowl vent tube depending on the carburetor your using. If you decide to use it, it can be (T) into the vent hose from the fuel tank.
Well that about it, I think that I’ve given you enough information and pictures to create an EEC system on your ride. As with all customizing and bring together of a number of parts from different cars/trucks and years you will be making the decision on what ones to use. Only you can hook it all up, you need to evaluate what you have and what you’re using.
Hay Chip, I did notice a possible problem on your engine (one of the last Pictures on your build thread) There doesn’t seem to be a filter cap on the opposite valve cover from your PCV valve. I’ve seen this problem many times especially when the valve covers have been changed to custom ones. Filtered air needs to enter the opposite valve cover for the PCV system to work correctly. If there’s no way for air to go into the crankcase the PCV valve will not be able to draw the engines internal fumes from the engine.
Enjoy your build
Bruce