Holley sniper return line question (2 Viewers)

[sfab]

Has anyone run a Holley Sniper return line back through the OE gas outlet port on the side of an interior gas tank? I have a 68-72 tank on my 66 and it is brand new (thank you Toyota!). I am curious if the return line pressure (supposed to be 3-6#) will be enough to overcome the pressure of gravity on a full tank, if there is indeed much.

thanks

 

[Skreddy]

What pump will you be running? I have the tanks Inc. in tank pump and it has a return port built in. An option if you haven’t picked a pump yet.

 

[sfab]

Sorry, I should have stated that- I already have an in-tank pump, made by Holley. It is technically a return-less model. I have had a few friends look at my set up and they've said it's better not to "dead-head" the fuel if at all possible. So I have been looking into that.

 

[GA Architect]

Sorry, I should have stated that- I already have an in-tank pump, made by Holley. It is technically a return-less model. I have had a few friends look at my set up and they've said it's better not to "dead-head" the fuel if at all possible. So I have been looking into that.

FWIW: My Sniper's fuel system, I use the supply and return ports on my '77 OEM gas tank. The 5/16" supply line off the tank steps up to 3/8" just after passing through the cab floor. The 3/8" return line off the Sniper steps down to 5/16" approximately in the same location, then to the tank.

 

[Steamer]

I am curious if the return line pressure (supposed to be 3-6#) will be enough to overcome the pressure of gravity on a full tank

If I’m understanding you question correctly.

As far as resistance to return flow, it doesn’t matter where the return enters the tank. The resistance to flow on the return will be determined by the height of the fuel that it is working against. Width or volume has no effect. Only height. It’s the definition of “head pressure” if you plumbed the return over the top of the tank and dropped in, the resistance to flow (head pressure) is simply measured by the height the fuel is pushed/pumped.

So yes, no problem plumbing the return to the bottom of the tank. My tank is custom, but the return enters the bottom.

 

[sfab]

If I’m understanding you question correctly.

As far as resistance to return flow, it doesn’t matter where the return enters the tank. The resistance to flow on the return will be determined by the height of the fuel that it is working against. Width or volume has no effect. Only height. It’s the definition of “head pressure” if you plumbed the return over the top of the tank and dropped in, the resistance to flow (head pressure) is simply measured by the height the fuel is pushed/pumped.

So yes, no problem plumbing the return to the bottom of the tank. My tank is custom, but the return enters the bottom.

Steamer, this is what I need to drill down on. Column inches is a concept that comes to mind. So in my case and for easy math, say my tank is 10" tall. The outlet port is somewhere around the 4-5" high range, but feeds to the bottom. So in my theoretical scenario, if I have a full tank (10" high), that is the "head pressure" I am trying to overcome? If so, I can find some math to work that out.

 

[Steamer]

There’s really no need to do any math. The resistance to flow in the return due to height is insignificant. The return is controlled by the regulator which maintains 60psi on the supply side and the excess gets passed to the return. If you increase the resistance on the return, you will still have the force of the pump pushing through.

If you were to put a gauge on the end of the return line with no other way for the fuel to get out, (dead headed) the regulator will pass anything over 60psi, and that gauge will end up reading the max output of the pump. Don’t try this because it’ll exceed 100psi. That is with the Walbro external pump anyway.

 

[sfab]

Bueno. Got it. Thx for the clarification Steamer.