As title says, have 4 vents on right side of tank. I am looking at a new tank from Holley, says stock replacement for my car, has only 1 vent on right side. I called tech support and he couldn't give me any info on why it only has 1 vent. For a non stock resto, do I need to have 4 vents tubes (and where do they all go) versus only 1 vent tube? I believe the fuel cap is also a pressure vent?

It could be a matter of a California emission issue vs 49 state.
I've seen 1970 Chargers with the 4 tube tanks and others with the single one.

This might help.

https://www.allpar.com/threads/fixing-1970s-and-1980s-fuel-evaporation-control-systems.229057/

Like he said most are California emissions.

The 4 tubes go from the tank to a vapor separator inside the trunk behind the passenger side rear wheel house.

There is no reason for it except emissions and can easily be removed.

There is an oval hole the trunk floor that the vapor separator mounts to. On my Challenger (single vent tube) the oval hole has a plate with a grommet for the vent tube to go up to the top of the filler neck. On the Cuda's I think there is a tube that makes a loop through the same plate.

Change over is just a matter of getting the tube and making or buying a plate.

Attached is a picture of both inside the trunk.

Factory venting covers all 4 corners.
Holley cost reduced that out.....

The idea with the four-corner venting and the different-height pipes inside the separator was that no matter what angle the car was at, in what direction, there would always be at least one vent fitting above the liquid-fuel level, so there would always be a vapor vent, thus preventing pressure buildup that would force fuel vapors out. The lines to the four tank-corner vents were relatively short inside the separator.

Fuel caps are different - vented vs not. Also the fill tubes may be unique to work in conjunction with the type of fuel cap needed? I think the tangs on the fuel caps need to match the fill tube opening, but don't quote me on it.

It doesn't hurt to keep the ECS gas tank setup if you have most of already there in place.

I have the big tube that is in the trunk.

IMGTX - Ok, so if I understand correctly, the 4 lines are not necessary and the 1 vent tube is plenty. For the 1 vent tube style, it loops up into the trunk, back down through the plate. Where does it go after it goes back through the oval plate? Oh, which parts houses carry that single vent line setup?

The vapor separator tank was required for all 1970 model year cars with N95 code which would include all CA sold cars.
In 1971 Federal mandates required them in all 1971 model year cars.

The 4 line systems are not bad but most 70's came with the single vent line which is apparently what Holley is making the tanks for.

On my Challenger the vent line starts at the top of the filler neck and goes through the plate and into the frame rail. Any fuel that gets through the tube would be dripped into the inside of the frame rail and vapors would be vented to the air inside the frame rail.

On my Barracuda it starts from the single vent line on the tank. Goes through the plate, loops in the trunk, and goes back through the plate. I have not looked, so I am not positive, but I would imagine it would go into the frame also. I will try to look at my Barracuda when I get home.

On a side note they got rid of the 4 line ECS used in 70/71 in 72 because it vented into the crankcase. In 72 it vents into a charcoal canister. I have heard rumors of gas fumes in the crankcase igniting and popping valley pan seals and valve covers. I have never seen it but I have heard rumors.

As far as the gas cap, it is different between the systems. I know they made different latches on the necks of the Challengers but I forgot if it is a year thing or a type of cap thing. On the barracuda's the cap can not leak under acceleration with either type cap, so a vented cap should work fine if it is made for a barracuda/cuda.

I know several places make the kits.

This is company that has everything you need in one kit. Look at part number EFV7001OM

https://www.sstubes.com/collections/fuel-lines-vent-line/Plymouth-Barracuda-1970

On a side thought, you could run one line to one of the 4 lines in the ECS vent/separator then cap the other 3. It should work fine.

Thanks for the info, much appreciated

That is a good idea, I think I will do this as the tank is on sale for a great price.

Just ordered, 109 bux with Holley's winter sale.

Actually they didn't get rid of it. In 72-up the 4 lines are on the front of the tank and go to a small vapor tank mounted up on the shock cross member. Also in 72 the charcoal canister was Added to the system.

Very true. I was trying to point out the 70/71 vented to the crankcase and in 72 they vent to a charcoal canister.

I worded it wrong.

Good Catch.

I am curious where you are getting a Holley Fuel tank for $108

Holley is having their winter sale. Get while supplies last. They have a bunch of stuff at nice prices. If you search by vehicle, it lists it as an “A” body in title but that is incorrect. The description is for the cuda. When I looked up the a body tank, it is different number and it has a reduced area for the spare tire.

Just saw this too, sign up for emails and get an extra 10% off. You can get tank for under 100!