1/4" return on sending unit

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73beast

73beast

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So I'm setting up my return style electric pump fuel system with a stock 73 dart tank. Have all 3/8 hard line (and -6an braided line), summit electric pump for carb mounted in front of the right leaf spring, Holley bypass style regulator set up after the 750 holley carb, and a spectra 3/8" sending unit with 1/4" return.
http://m.autozone.com/fuel-delivery...ding-unit/dodge/dart/796728_70445_0?location=

The issue I'm having is the 1/4" return port at the sending unit is causing a bottleneck making minimum pressure 8.5psi at the carb, and the carbs not liking it. Have tested dumping my 3/8 return line into a bucket and the pressure is a good 4psi which I can adjust up from there at the regulator. I'm aiming for about 6psi.

The question is has anyone else had this issue? Any better sending units out there? Because all I've seen are identical parts with different brand names.
I'm tempted to drill out the 1/4 return line and weld/braze in a 3/8 steel line that actually runs to the bottom of the tank, but am not sure how to prevent the level sensor plastic seal from melting... Another option that I'd rather not go with is drill out my tank for a -6an bulkhead fitting, and hope it seals.
Any tips would be appreciated!
 
Worst case scenario you can pull the filler tube and install a 3/8th hook up for the return there

Well, that's not completely true...i guess WORST case scenario you could trade it for a chebbie
 
3/8 supply and 1/4 return just won't work, because the amount of fuel being sent back is too great for the line to handle. I tried it a long time ago. Sorry to say, the best (and more expensive) solution was a new Tanks Inc. tank with in-tank Walbro pump. These tanks come with already-installed 3/8" sized supply/return fittings that can be adapted to -6AN or equal.
 
Solder in your new fitting not weld or braze. I used to rebuild sending units and repair gas tanks and that is the best way to do it.
Mike
 
73beast said:
So I'm setting up my return style electric pump fuel system with a stock 73 dart tank. Have all 3/8 hard line (and -6an braided line), summit electric pump for carb mounted in front of the right leaf spring, Holley bypass style regulator set up after the 750 holley carb, and a spectra 3/8" sending unit with 1/4" return.
http://m.autozone.com/fuel-delivery...ding-unit/dodge/dart/796728_70445_0?location=

The issue I'm having is the 1/4" return port at the sending unit is causing a bottleneck making minimum pressure 8.5psi at the carb, and the carbs not liking it. Have tested dumping my 3/8 return line into a bucket and the pressure is a good 4psi which I can adjust up from there at the regulator. I'm aiming for about 6psi.

The question is has anyone else had this issue? Any better sending units out there? Because all I've seen are identical parts with different brand names.
I'm tempted to drill out the 1/4 return line and weld/braze in a 3/8 steel line that actually runs to the bottom of the tank, but am not sure how to prevent the level sensor plastic seal from melting... Another option that I'd rather not go with is drill out my tank for a -6an bulkhead fitting, and hope it seals.
Any tips would be appreciated!
Click to expand...

A person might find this a bit tedious to do, but I drilled the return in the sender plate and soldered copper tubing into each end of a brass allthread pipe like used to put lamps together with the fiber sealing washers and nuts inside and out.
Then used 3/8 nylon 12 EFI line from up front back to the tank.
Just a possible alternative for you if it helps.
 
69_340_GTS said:
3/8 supply and 1/4 return just won't work, because the amount of fuel being sent back is too great for the line to handle. I tried it a long time ago. Sorry to say, the best (and more expensive) solution was a new Tanks Inc. tank with in-tank Walbro pump. These tanks come with already-installed 3/8" sized supply/return fittings that can be adapted to -6AN or equal.
Click to expand...

Found this
http://magnummopar.com/articles-and-how-to/tag/Walbro
Looks like what you suggested. Wish I would have seen it earlier, before I spent $ on making my tank work... I agree it is the best option especially considering the tank is baffled and in tank pump. But close to $500.
 
TrailBeast said:
A person might find this a bit tedious to do, but I drilled the return in the sender plate and soldered copper tubing into each end of a brass allthread pipe like used to put lamps together with the fiber sealing washers and nuts inside and out.
Then used 3/8 nylon 12 EFI line from up front back to the tank.
Just a possible alternative for you if it helps.
Click to expand...
Good idea! What kind of sealing washers did you use?
 
73beast said:
Good idea! What kind of sealing washers did you use?
Click to expand...
I used the fiber washers that came with the lamp repair kit.
A light coat of brush on type aviation Form a Gasket on both sides of both washers and it worked perfectly with not even so much as a damp spot around it after about a year of running.
FYI, I bought a regulator but didn't use it.
I put a pressure gauge on the supply side at the carb and added a restrictor in the return to give me 5.5-6lbs and then took the gauge back off and reconnected the line. (no gauge, no regulator and exactly the pressure needed)
Still have the brand new Holley regulator sitting here.
Just put the nuts on the tube before you solder the copper on as taking the nut back off before installation will help clean up the threads if they got any little bit of solder or flux on them at the ends.:D
Most any hardware store has these lamp repair kits.

319Ou-ocsgL.jpg
 
Last edited:
15041288151502131790463.jpg
So I'm going to end up using the bulkhead fitting I already have. Not going to crowd the sending unit, so drilling the tank at the circle in the picture, and keeping it high so it's not always sitting in fuel. Going to attach a 3/8 aluminum tube to the back side of the fitting down to the bottom of the tank to reduce splash. And just plug the 1/4" tube.

By the way had to bend the crap out of the pickup tube on the sending unit, was 2.5" above the tank floor. And fingers crossed on fuel level gauge being accurate.

Would have liked the aftermarket tank much better, but going with the simple quick and cheap fix. Thanks for the input guys!
 
In case anyone is curious this is how the tank turned out
20170908_161426.jpg

20170908_161809.jpg

The flash may have the clearance hard to tell, but the return line is 3/8" off of the tank floor, and the pickup screen has a 1/16" gap off of the floor.
 
Assembling that return line inside the tank was like building a ship inside of a bottle.
 
Now explain to me why the return line had to go to the bottom of the tank....
Im sure I missed something here.
And why mount it so high in the tank instead of parralel the the send unit and pickup?

This is a real question... No sarcasm intended...
 
mbaird said:
I think I figured out the high mounting...
Click to expand...
May not be necessary for either, but I'd rather put the bulkhead fitting above the usual fuel level. I'm sure it's leakproof, but I'd rather give it every chance to succeed. Also looked cleaner with how I routed the fuel lines outside of the tank.

Ran it to the bottom to kill splash. With the built in return line on the sending unit I could hear a sound like someone peeing in a pool from 20+ yards away. Not foaming up the fuel is a plus too.
 
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