Fuel return line and venting

[socalliving]

Have a Backdraft with aluminum tank. There is a -06 an bulkhead fitting that is currently capped almost at top(vertical part of tank)facing towards the front of car. Can/should I use this to place a fuel vent valve? Rollover valve? My return line is tee’d into the filler tube.

I have a g-surge high pressure pump in the engine compartment. It requires a full return line to the tank. Still using low psi pump at tank in conjunction with this high psi pump. Also, have a Fitech EFI TB.

When my racing cap is closed it is tight, meaning it is not allowing any air into the fuel tank/system. Won’t this cause a vacuum in the system?

Not sure if my tank needs to be vented or not and if this bulkhead fitting should be used as a place for returning fuel or venting.

Steve

[Morris]

Originally Posted by socalliving

Have a Backdraft with aluminum tank. There is a -06 an bulkhead fitting that is currently capped almost at top(vertical part of tank)facing towards the front of car. Can/should I use this to place a fuel vent valve? Rollover valve? My return line is tee’d into the filler tube.

I have a g-surge high pressure pump in the engine compartment. It requires a full return line to the tank. Still using low psi pump at tank in conjunction with this high psi pump. Also, have a Fitech EFI TB.

When my racing cap is closed it is tight, meaning it is not allowing any air into the fuel tank/system. Won’t this cause a vacuum in the system?

Not sure if my tank needs to be vented or not and if this bulkhead fitting should be used as a place for returning fuel or venting.

Steve

Yes.....use the top of the fuel cell (AN-6 fitting) as the return line......and vent the cell thru the gas cap....with some AN-6 check valves so fuel can’t escape but will let air out....

Go to Summit and look for AN-6 fuel check valves

[twobjshelbys]

Originally Posted by Morris

Yes.....use the top of the fuel cell (AN-6 fitting) as the return line......and vent the cell thru the gas cap....with some AN-6 check valves so fuel can’t escape but will let air in......

https://www.summitracing.com/parts/s...192b/overview/

Is anyone seeing the summit link? Every time I click it I'm highjaked to some "viglink" site that tries to sell me sunglasses!

[Gaz64]

Originally Posted by twobjshelbys

Is anyone seeing the summit link? Every time I click it I'm highjaked to some "viglink" site that tries to sell me sunglasses!

Yes, link must be posted incorrectly.

[socalliving]

Thanks Morris.

I also had to drill a 1/8” hole into the plate that is underneath the Lemans style race cap otherwise it was a tight seal due to the o-ring. I didn’t use the an-6 on the tank but tee’d the 3/8” line off the Moroso filler tube. So the fuel is returning to the same location as it would if filling the tank. It seems to work fine with no issues. Unless somebody else sees an issue with that please let me know.

Thanks

Steve

[socalliving]

Re: my previous post. the line off the filler tube enters the tank at the rear at the highest point vertically on the tank. Same as the other an-6 fitting that is capped. However the returning fuel is now further from the pickup point by the low psi pump. If I think about this logically this is doing the same as if I would’ve used that capped fitting as my return entry location, right? I think?

Anyways, any more input would be appreciated.

Thanks

Steve

[CompClassics]

If you have a roll over flap on the fuel filler pipe is the return line before or after the flapper? If the return line is before the flapper than you could have a problem in the event of an accident where the fuel could be allowed to escape the fuel tank more easily than if the return line was on the fuel tank side of the flapper. I would do as suggested above and put the return at the blocked off port at the top of the fuel tank and run the fuel tank vent with a rollover valve to the fuel tank filler pipe.

[socalliving]

CompClassics, note well taken. I do not see any flapper in the filler neck when looking down from the top. Unless its some sort of ball style that I can’t see. I assume this has to be placed in the vertical position of the neck for it to function properly.

Therefore if I move the return to the capped fitting I should install a flapper in the filler neck. I assume that requires removing the entire filler neck assembly to install one.

BTW your not far from me. Belong to the local cobra club?

Again thanks for the input.

Steve

[socalliving]

Also, the return fitting I’m using now is 1.5” higher on the tank, when measuring from ground to center of fitting, compared to the capped fitting. Not sure if this really makes any difference. But it is further from the pickup so I’m not dumping warm fuel near the pickup.

[CompClassics]

socalliving,
Our shop is located in Escondido, you are welcome to stop by anytime. We may have crossed paths at Cruzing Grand?

[Morris]

Steve

Here's what you want....first you want to set up the ability to vent the Fuel Cell then Block it in case of a Roll over situation. So we start with a Aero Cap inside of the Cobra Cap.... and this gives you a space between the Aero Cap and the Flip Cap which is what you need to mount the AN-6 fittings for the vent lines



Now you need to drill some holes to the atmosphere for the ventilation of the fuel cell.



When the Aero Cap is closed and the Cobra Cap is closed the air can come up into the space between the two caps and vent through the holes you drilled.



Now you see the AN-6 Nipples and 90*degree fittings for the fuel cell... one for each side of the tank, so when it's full you don't have any issue with venting from one side or the other.



This is the Passenger side vent .... and if you notice it has a check ball in it so you are protected of a Roll over on that vent line ... but the AN-6 fitting on the other side of the Fuel Cell does not have a check valve in it line...



Now you can see the under side of the Fuel Cap .... this shows the two AN-6 90* fitting coming out of the cap and the two vent hoses attached to the fitting and below the fitting you see the AN-6 Check Valves in line to stop the fuel from coming out.... Also remember the most important item in this photo is the Grounding of the Cap to the Frame of the Vehicle so you don't get any Static when Fueling...



Here's the other side of the Cobra Fuel cap showing the AN-6 Check Valve on the other vent line so no fuel can escape during a roll over or accident.
Again check out the Ground Straps.

Sorry for the long Post ...but there's no easy way to say it...

[socalliving]

Thanks Morris.

I drilled one 1/8” hole like you did on the cobra cap. Do you really need so many holes? The purpose is to prevent a vacuum, right? My fuel cell and filler tube is is a little different.

I have the capped fitting which is behind the driver side and the other fitting is being used for the 1/2” line which is coming off the Moroso tube and is pointing down. This line(off the filler pipe) enters the passenger backside of tank.

I was going to place a rollover valve on the drivers side fitting.

I post some pictures.

Thanks for the photos.

Steve

[Gaz64]

The venting needs to be good enough to replace the fuel the engine is using at peak consumption.

So 600 hp, 300 lb/hr, 5lb/min, about 1 gallon/minute, about 4000cc/min. 66cc/sec.

Can a 1/8" hole flow that much air?

There are other ways to have to filtered air as a venting supply.

Gary

[Morris]

Originally Posted by Gaz64

The venting needs to be good enough to replace the fuel the engine is using at peak consumption.

So 600 hp, 300 lb/hr, 5lb/min, about 1 gallon/minute, about 4000cc/min. 66cc/sec.

Can a 1/8" hole flow that much air?

There are other ways to have to filtered air as a venting supply.

Gary

Gary

Very nice comment.....I especially like the calculation......and that is why we have many holes..........we are running 750 plus HP and it’s using a lot of fuel....and air....

[Gaz64]

Originally Posted by Morris

Gary

Very nice comment.....I especially like the calculation......and that is why we have many holes..........we are running 750 plus HP and it’s using a lot of fuel....and air....

Thanks for the comment Morris.

Love your photos, keep them coming.

Gary

[Morris]

Bill

You noticed something that most don’t.....the second ground strap that goes from the fuel cell inlet mount to the chassis ground....

When we mounted the fuel cell we put silicone rubber between the straps under the cell that support the fuel cell....and the cell.......so we needed to ground the cell again

And we needed to make sure we had a good ground for the Fuel sending unit to work.....

Static spark was the reason for the fuel cell cap ground.....you can’t have enough grounds .....

[Gaz64]

A few of us did notice your ground straps, and we know what they do, .

Static discharge at the filler neck is an issue with some cars that have poor grounding at the neck. Seen some fire damage from this.

Love the use of braided ground straps.

Gary