Evaporative Control System

1968 -1970 Mopars

  1. Grabinov911

    Grabinov911 FBBO Gold Member FBBO Gold Member

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    Hey Gents,

    I have a 1970 RR California car with the Evaporative Control System (ECS). that means that in addition to he fuel line, my tank has four hoses which run from the passenger side of the tank up into a canister in the trunk, and a steel fuel line which then runs forward all the way to the engine bay where it, theoretically, allows fuel tank vapors to be consumed by the carb when running, or carb vapors to condense into the tank when parked. By modern standards, this emission control system is a joke, particularly given that the Holley carb I am running does not use that line!

    So can I just cut off / block off all of those lines at the tank? One of them may be necessary as a tank vent (I'll check) but the others just seem like needless extra complexity. This is a mechanical question, not one of legality. I assume that I should not tamper with the factory emission system, even such as it is, but really, it's a joke. Carb vapors? Seriously?

    Greg
     
  2. 72RoadrunnerGTX

    72RoadrunnerGTX Well-Known Member

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    The ’70 ECS system is an early version of same evaporative emissions containment systems almost every car on the road has today. The canister in the trunk is simply a liquid/vapor separator insuring the hard line running forward only contains fuel tank evaporative vapors. In ’70 this line was connected to a three nipple crank case breather on the passenger side valve cover. The intent was for these vapors to be stored in the crankcase while the vehicle is at rest and consumed via the PCV system at start up rather than allowing these unburned hydrocarbons to escape into the atmosphere. Later years used a charcoal canister to temporally store these vapors. The vapor return line also acts as the fuel tank vent system, if you plug it all off you will need to provide another tank vent.
    71fueltankr.jpg
     
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    • moparmarks

      moparmarks FBBO Gold Member FBBO Gold Member

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      I wounder if the reproduction tanks have that thermal-expansion volume tank in them.
       
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      • 383man

        383man Well-Known Member

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        I have plugged the lines on some of the cars I have done that were basically turned into hotrods. After plugging the lines I just ran a vented gas cap. If you do that just make sure you can get the vented cap. If not use one of the lines for a vent but just run it so no gas can come out of it. Most muscle cars out there have their evaporative lines unhooked or removed. Only the full stock restorations still use them. Ron
         
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        • RustyRatRod

          RustyRatRod Well-Known Member

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          Yes, your Holley does have "that line". They all do. In fact, it has two. They are the float bowl vent tubes.
           
        • 72RoadrunnerGTX

          72RoadrunnerGTX Well-Known Member

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          The single enclosed bowl vent valve fitting present on the OE ECS carbs are not on β€œall” Holleys, specifically non-ECS OE and most aftermarket/race versions do not have enclosed bowl vent valves and its related hose fitting. The vent hard line to the tank never connected directly to the carb. The carb vent valve fitting connected to its own breather nipple in '70-71, again to recover and store evaporative vapors from the primary fuel bowl while the vehicle is at rest, consumed when running.
          A well maintained and intact ECS system has no negative impact to engine/vehicle performance, you gain nothing by disabling a functioning system.
           
          Last edited: Mar 8, 2013
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          • RustyRatRod

            RustyRatRod Well-Known Member

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            ALL 4 barrel Holleys have float bowl vents. That was my point. You are absolutely 100% correct about disabling the vent system. In fact, it can and usually does have a negative impact on mileage, since one of its promary functions is to return fuel vapor BACK to the tank. Fuel vapor=FUEL which condenses back into the tank once it cools. A good return system also serves the same purpose.
             
          • Grabinov911

            Grabinov911 FBBO Gold Member FBBO Gold Member

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            You guys are awesome...

            EXACTLY! The tank I used from Classic Industries appears to have weld marks on its top which suggest that it does in fact have that expansion volume. I also DO have a vented gas cap, and my plan is to leave the canister in the trunk with one line running to it as a vent just in case. I am asking about removing the system only because I don't need a bunch of useless lines running around under the car - I do agree that it otherwise has no negative performance effect on the car.

            The only reason that I am removing my new tank is that, in the interest of "restoration-ism", I reused the 40 year old pad which fits between the tank and trunk floor when I installed the new tank. That pad promptly disintegrated and slid, in pieces, out from between. Now, at a stop, at idle, in gear, under just the right conditions, the tank top and trunk floor vibrate against one another and make a metal to metal howl that would drive any auto enthusiast nuts! So I have to unhook all those durn hoses t get the tank out. Why put em back...

            Thanks guys. I'm off to the garage...

            Greg
             
            Last edited: Mar 8, 2013
          • 383man

            383man Well-Known Member

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            The Holley bowl vents might be confusing to some. All Holley carbs on cars with evaporative systems had at least one carb external bowl vent that would open at idle. Then all Holley four barrell's have the 2 internal vents in the air horn. The idea was the external vent was open at idle with the car on or off to vent carb bowl fumes to the crankcase or charcoal canister depending on the system. But off idle the external bowl vent should close so the carb will be internally balanced by the internal vents in the air horn which are the ones many racers join together with a rubber fuel hose and cut a hole in the hose. Ron
             
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            • hsorman

              hsorman FBBO Gold Member FBBO Gold Member

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              I also have a 1970 California road runner with the Evaporative Control System (ECS).

              While I currently plan to put the system back on (the return line was cut and plugged), I've also been thinking about maybe using that line as a fuel return line. Either for fuel injection or just to keep the fuel cool.

              Thoughts?
               
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              • 383man

                383man Well-Known Member

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                Very good idea. I have been considering putting a return line on my 63 with my electric fuel pump but I will have to rig up a return line setup. Yes its a great idea. Ron
                 
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                • mobbody

                  mobbody New Member

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                • mobbody

                  mobbody New Member

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                  I would just cap the carb line at the crankcase breather air cleaner and keep the other two connected.
                   
                • oldbee

                  oldbee FBBO Gold Member FBBO Gold Member

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                  If "THEY" ( EPA,state) aren't checking, there's your return line & screw the rest!
                   
                • hsorman

                  hsorman FBBO Gold Member FBBO Gold Member

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                  This is an old thread, and since that time (from my post #10 above), I have restored my car. I bought two Hemi (3/8) fuel lines for the car. One is the fuel supply and one is the return. I have a throttle body fuel injection system and a fuel pump in a custom gas tank.

                  The system works great and I am very happy with it. No vapor lock, fuel issues, evaporating fuel making for hard starting, etc. It just works great.

                  Hawk
                   
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                  • 383man

                    383man Well-Known Member

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                    The only time an evap system will effect the eng is when its purging. On the early ones where the fuel tank and carb bowl vent lines go into the breather on the valve cover as soon as the eng starts it pulls any stored gas vapors in the crankcase into the eng through the PCV system. So it could make the eng a little rich on startup. If its the later system with a charcoal canister they usually will purge at part throttle so when it purges the fumes that are stored in the charcoal canister the eng may run a little rich for a minute or so. On newer fuel injected cars Mopars have a purge free and purge adaptive memory cells so the controller will lean the fuel mixture a tad when its purging running in the purge cell. Ron
                     
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