Topic: Using a std gas tank with emissions system

[RocketScientist]

I need to replace the emissions gas tank on  my 70 B302 and I intend to use a std tank with the original filler neck to preserve the look. As the gas cap is the non-venting type will I run into problems with fuel flow and creating a vacuum inside the tank?  I have seen some drill a small air bleed hole in the filler neck near the cap and I was wondering if it is necessary?
Brad

[J_Speegle]

Believe the vent hole needs to be located in the cap so that it vents/breaths to the exterior of the car. Venting the neck will produce gas vapors into the trunk and in turn into the interior of the car. NOT what most people would want nor is it a safe idea. But yes you will need a vented gas cap

You could do something like the 69 retrofit (there is at least one thread about that here on the site) for Shelby's but it included the venting of the neck of the filler and a vent over and out through the passenger side

For the "original look" have you figured out how your going to join the filler neck and the tank so that the large tank end bell shaped rubber hose?

[RocketScientist]

Working out the attachment of the rubber hose was going to be the next item on the list to tackle. Having the best intentions of keeping the original look is sure causing a few headaches.

[J_Speegle]

Working out the attachment of the rubber hose was going to be the next item on the list to tackle. Having the best intentions of keeping the original look is sure causing a few headaches.

Always part of the fun and challenge   Think the bottom wider end will be pretty easy to do - Hiding the upper difference is going to be the fun part. Good luck with the project

[69bossnut]

On a 69/70 standard tank the cap is not vented on the original caps. So you should not have any issues converting to a standard tank & cap. There are some caps that I have come across standard tank caps that are vented. So either way you should be ok.

[Bob Gaines]

The standard Mustang /Cougar gas caps and filler necks for 65-70 were designed to be vented but on the 69/70 CA emission system the caps were designed not to be vented because the gas fumes were instead routed to emission system. If using a standard gas tank and adapting the emission filler neck and using the emission non vented cap you WILL have problems like you suspect. The fuelpump may or may not be able to overcome the vacuum created by trying to pull fuel from a closed up fuel tank without air to displace it. However there is a easy solution. You will need to do exactly like what was done for the 69/70 Shelby GT500 vent recall. In that case the vented cap was replaced with a non vented cap (so fumes could not be ignited by center exhaust port during a backfire) . The short explanation is that the the filler neck was vented by adding a nipple to the filler neck and using 3/8 fuel line the filler neck was vented to the passenger side and down the trunk drop to the out side . I will try and dig up the Shelby vent recall instruction and illustrations and post unless Jeff Speegle bets me to it-I hope .

[KevinK]

Working out the attachment of the rubber hose was going to be the next item on the list to tackle. Having the best intentions of keeping the original look is sure causing a few headaches.

If you are looking for a hose to adapt the connection, they make quite a variety in silicone hose adapters for air intakes. Unfortunately, the are not stock looking.

[RocketScientist]

I noticed that the std gas filler neck was notched near the cap to enable venting and I was wondering if it would work if the emissions filler neck was notched in a similar way?

[J_Speegle]

I noticed that the std gas filler neck was notched near the cap to enable venting and I was wondering if it would work if the emissions filler neck was notched in a similar way?

Likely so as long as the gasket does not compress in that spot and restrict the venting

[Bob Gaines]

Here is a illustration of how the 69/70 GT500 had to be modified so as to vent the filler neck fumes to a different location. You could use this in your situation if you choose to use the factory filler neck and non vented gas cap.

[RocketScientist]

Thanks for the schematics Bob and it is good to know that there is a solid solution possible. I am also concerned that the gasket could restrict the venting but I will give it a go, knowing that it may cause me problems and worst case I will revert to the conventional venting gas cap. There's no harm in giving it a go and seeing where I end up.

[J_Speegle]

Of course the use or installation of the Shelby Fix will be visible (more on your Boss than even a Shelby) and negate the efforts of trying to camouflage what your attempting to do.

Did notice before that the notch on the filler neck is mentioned in the Shelby recall paperwork. 

We had pictures and the diagram posted in another thread on another site. Guess its time to create a thread and post it all again here for the GT500 Shelby owners

Opps - Found it here

http://www.concoursmustang.com/forum/index.php?topic=17420.0

[69bossnut]

I was stating that if went to a standard tank, standard neck, & standard cap he would not have any issues. That’s what I thought he was asking. I guess I missed the part about using his ca emissions neck & cap.

[Bob Gaines]

I was stating that if went to a standard tank, standard neck, & standard cap he would not have any issues. That’s what I thought he was asking. I guess I missed the part about using his ca emissions neck & cap.

No worries .Been there done that more time then I care to remember.