Fuel Tank plastic attachments in trunk info req'd

[v8ford70 98]

My 1970 Coupe fuel tank has a plate covering where this plastic part attaches to the tank in photo( photo attached is not my car but for reference).The previous owner had it disconnected but I did get it with the car.Can someone tell me what this plastic set up does.Is it required to be fitted? I don't know if it has anything to do with working out what sort of fuel cap I should have fitted vented or non-vented? (no pollution gear is attached to motor).My unfinished car is just parked in my shed & I'm having trouble with fuel leaking out of my 600 Holley pooling fuel into the dips along both sides of the new Edelbrock performer inlet manifold below carby. Could it be due to the high temps here in Queensland Australia at present (35 deg C) that the fuel tank is pressurizing ? Any help will be much appreciated.Cheers Phil

[Mach1 Driver 560]

Some of the 70 people will have to speak-up here, as that plastic stuff isn't on a 69. On my Mach the fuel line and fuel gauge sender are on the same plate which rotates in to seal and are located on the front side, near the top and middle of the tank. The tank is vented through a little relief in the fuel fill pipe sealing surface. Unless 70s were changed substantially, that's aftermarket.

[69ShelbyGT350H 61]

It seems to be part, or a complete gas vapor system. Possibly for California cars.

http://forums.vintage-mustang.com/vintage-mustang-forum/1035266-fuel-tank-vapor-vent-separator-71-mustang.html

[Brian Conway 264]

As mentioned Fuel vaor recovery is a 70's thing only.  Suggest you take another look at your carb, fuel lines and throttle cable set ups.  Brian

[1969_Mach1 333]

1970 was the first year for vapor recovery systems on all makes.  Basically, the fuel vapors from the fuel tank and carb are collected in a canister filled with a charcoal medium.  Some call it a Carbon Cannister, some call it a Charcoal Cannister, some call it a Vapor Cannister.  The medium absorbs the vapors.  When driving (not at idle) the vapors get purged into the engine through a vacuum hose connected to the canister.  There should be a canister mounted somewhere unless a previous owner removed it.

The car will run just fine without this system connected as long as the fuel tank and the carb bowls are still vented to atmosphere.  If you want something concourse correct, then you need all the correct components.  Note, if it has the carbon canister installed and it is only connected to the fuel tank and never being purged when driving, it will eventually become saturated with fuel vapors and you will smell them.  I guess that situation can become dangerous.

[v8ford70 98]

1969_Mach1 I have no charcoal vapor canister from previous owner, all I have are the plastic parts  as in the above attached photo that would go in the trunk.The previous owner attached a metal cover plate over the hole in the fuel tank where one of the plastic covers would have attached(as in Photo).The plastic parts are connected with tubing ,I don't think there is any place for a tube to attach to these parts & go to the motor I will have to check out tomorrow.Has any 70 owner got this set up connected in their trunk & no cannister up front on motor,or neither connected.You may be able to let me know whether your fuel cap is vented or not.My tank being plated if the fuel cap I have is non vented could this send pressure to carby & make it leak?Thanks everyone so far for your input.Regards Phil

[1969_Mach1 333]

Usually what happens if a fuel tank is not vented is the carb eventually runs out of fuel.  As the fuel level in the tank drops, air must enter the tank to compensate for the volume reduction of fuel. I guess your thought is possible on an extremely hot day if the gas cap was only previously opened on a cold day.  But never seen or heard of that.  If your carb is leaking it probably needs to be rebuilt including a new float.  

[v8ford70 98]

I have pulled the 600 Holley carby off Manifold & stripped it down ready for cleaning & then to install new Holley carby kit.I came across on the Holley web site in questions and answers that they said that fuel from carby can percolate with heat transferred from engine & leak onto intake manifold,they suggested a Plastic Phenolic carby spacer  could solve problem.Has anyone had this fuel leak problem & used one of these spacers? Also has any 70 owner removed the plastic set up on their fuel tank or has it set up on their tank as in above photo.PM me if you prefer as I still require info.Thanking you Phil

[Mach1 Driver 560]

I traced the origin of this. In 1970 in California only, Ford came out with the vapor canister system for the tank only. They improved it and put it on all cars from 71-73. The 71-73 tank is substantially different. It has an air space at the top with a vent tube that runs over to the fill pipe and mates with a baffle in the fill pipe. These cars also have a floor in the trunk, not like the older cars that use the top of the gas tank as the trunk floor. There is a vapor/fuel separator that connects to the top of the tank at the air gap.That goes to the vapor canister and from there to the air cleaner. Since the plastic parts become very brittle and it was only used in California for one year, there aren't many of those parts still available. It may be easiest to go with a 69/70 tank (used in all the other states) and fill tube. That fill tube has a little indent tooled in the gas cap sealing surface (at the top) which becomes the tank vent.

[LoneWolf2U 136]

Yes this is the vapor recovery system for 70 and up. You need to have a vented fuel cap for your tank if this system is not going to be connected or it will pressure feed the carb with vapor expansion.

As for the leaks it is coming from the pressure over riding the float from the tank trying to expell vapor.

reseal the carb and check float levels

Yes using at least a 3/8 spacer under your carb to keep heat soak to a minimum is a good idea, They are available at most parts stores.

[v8ford70 98]

Thanks everyone for your info.I have purchased a 1/2"  Plastic Phenolic carby spacer & carby parts have been cleaned & ready for re-assembling in next few days,then back on motor with  new spacer. I have attached photos of my fuel tank fill tube.Looks like the previous owner drilled a small hole as a vent near where fuel cap seals? I have also attached photos of my fuel cap which I presume is non vented.Do you think that this drilled hole in fill tube is big enough to vent the fuel tank? and a non vented cap will still be ok to use.

[LoneWolf2U 136]

Your good to go, Hole is more than needed for venting.