To me it looks like they were making sure all trapped air (some would be gas vapor) at the top of the tank is taken out of the tank and put in the evaporator tank, I assume for environmental reasons to prevent it from escaping to the atmosphere. Picture the tank rocking forward and back and side to side as might happen if the Z was going down the road or is parked on an incline as it is being filled with gas and how those vents are placed so that one is always at the top of any bubble of trapped air that might form. Why getting the trapped air out might be important I have no clue.

Edited June 7, 201410 yr by Mikes Z car

The tank to evaporator hoses and filler pipe circulate the gas from liquid to vapour to liquid. I thinks the four hoses are for drain back and for collection at the highest locations. The three pickups on the tank seem to prevent trapped pockets of gas vapour

The tank to engine compartment line is the only opening in the system where fresh air can be drawn back to the tank to replace the fuel that is consumed when running. The fresh air is drawn through the carb's air filter box.

When the car is stopped and off, the line to the engine compartment also sends fuel vapours to be be stored in the crank case (when heat causes the fuel tank pressure to increase)

The flow guide valve either sends tank fumes to the crank case or fresh air to the tank.

I recently replaced all hoses on one of my Z's. It appearance that the multiple vapor hoses are needed due to the baffling in the tank (which minimizes gas sloshing around). The baffles essentially create separate pockets at the top of the tank, and each needs to be vented. It seems to me that they could have collected them together in a manifold and then sent one or two hoses back to the recovery tank, but why make it easy on yourself?

look at your rubber insulators that hold the fuel and brake lines, if the ones in the transmission tunnel and the one in the center of the firewall above the transmission have 4 holes then you have or had the piping for the flow guide valve. If only three holes then no flow guide valve.

steve

Here's a pic for the guidance from Steve. The vapor return line is on the driver's side frame rail.

I can't believe very much fumes are going to make it out of the evap tank, down the long 1/4" tube, and out into the engine bay, especially since air is supposed to be going the other way when you're driving. Nice idea, but I doubt if it does very much except vent the tank, which is necessary.

If it turns out you have the tube (shown clearly in the post above) but no flow valve, you could just leave it as is. If the tube is disconnected at the evap tank, maybe put some emission hose on it and let it go down under the car, to keep any fumes out of the cabin.

Anybody with a flow valve, give that thing a good blast of carb cleaner so it actually works.

Edited June 9, 201410 yr by Stanley