When do you use a return fuel line?

[mikes68charger]

I have a 68 with a good 360 motor. I'm running 3/8 stainless steal lines to the filter then pump Blue Holley electric) which then turns into 1/2 stainless all the way up to the regulator which is on the fire wall, back down to 3/8 stainless.  My problem is I'm using the Hemi fuel sending unit / for the bigger pick up tube, but it has a nipple for a ruetun line. I'm not using one and I don't think I have had a problem with it running low. SO How should I plug the return line nipple or should I some how use it.

[Steve P.]

Hey Mike.. You've got some good questions there. You didn't mention if it's an aftermarket 1/2" or factory style 3/8" sender. I am guessing you went with the 1/2 inch as they run about the same price and why not??

Let's start with the feed line.  The ideal feed line would be to use the biggest suitable lead line from the tank to the pump. You never want to starve the pump. Electric fuel pumps like yours are built to push fuel, not pull fuel. So since you have the 1/2 inch sending unit you should be using a 1/2 inch feed to the pump.  Also the pump should be mounted just below and as close to the tank as possible for best performance.

From the pump forward:  You could use the 1/2 inch. line that you allready have in place without any trouble. In most cases more volume is better. The only real problem with using a large line here is if it ends up too close to your exhaust. The bigger the line, the more heat is absorbed and the longer it takes to change the source fuel. With a 360" you will probably never use the amount of fuel that the 1/2" line will produce. If you plan to use No2 the 1/2 line would help, but a stronger pump would probably be called for.  You could easily use a 3/8" line from the pump forward.

The regulator: Great idea. Only I take it yours does NOT have a return port. I recommend using a regulator with a return line to the tank. It's not necessary, I just like to have fuel running in a constant loop back to the tank. This helps with heat in lines and will help keep your fuel pump running cooler and for a greater amount of time.

The return line: For most street applications you can get away with using the 1/4 inch return port in the sender. My opinion, and again I say, MY OPINION is that the return line and the return port back in to the tank should be the largest ID. of all on the car. This is the way that many other systems are built. Smaller lines for higher pressure and larger lines for lower pressure.  Your AC lines are this way. The feed and return lines at your local gas station are this way. Your steam heater is this way. Many pump manufacturers require it this way.   The Barry Grant web site has some pretty good drawings of this. 

You could plug off the return at the sender with a FUEL USE nipple plug from your local parts store. If you do, make sure you use a clamp on it to make sure it doesn't drop off and start picking up road dirt.

Take a look here: http://www.barrygrant.com/bgfuel/default.aspx?page=85 The third system down is what I like. 

Hope this helps. Any other Q's, don't hesitate to ask..

Steve

[8WHEELER]

I am betting that his sender is 3/8in fuel and 1/4in return, I have never seen 1/2 in fuel with a return line.
The people that I have seen and used only have 1/2 senders with no return, but maybe somebody is
making one now, you can make most anything 

And as so well stated    put the pump in the rear. In 82 I bought a charger that ran a pump in
the engine bay, it kept getting hot and wearing out because it was pulling fuel and getting hot the hole time.
The cam had gone flat on the prier owner, so instead of a new cam he ran a pump go figure 

Dan

[Steve P.]

Dan, I believe you are right.. I was looking into a 1/2 inch sender for my 65" Coronet. Non of the 65 stuff I found had the return, but when I was looking one up for VegasMike I Figured on tapping the tank for a 1/2 inch return. Now I can't remember what is on his 68!!   


At any rate, it is rather easy to remove the 1/4" tube and replace it with 1/2". A cut off tool, drill and a bit of grazing. If you can't braze it in you can take it to a radiator shop and have it done pretty cheap.. 

[mikes68charger]

Its a Electric Holley with the Holley regulator. I am currently using the return port on the regulator for my fuel pressure gauge. I guess I could run a 1/4 return line with little existence. If you all say its worth it I will do it. The electric pump is located on the frame in front of the rear axle.

[8WHEELER]

Well it is not a necessity to run a return line, you can get by fine without one. My wife drove her 68 RT Charger
every day to work for 15yrs with no problems, and I had the return line plugged off because I could not find
a replacement fuel vapor separator 24yrs ago 

I now run the 1/4in return line mostly just for stock 68 440 HP correctness, you know car show points 

But it can help with any car, sometimes people have issues and try everything, then hook up a return line and that
has solved there problem, it has happened on this site a few times. Anyway its really not necessary, but for piece
of mind I hook it up.

Dan

[Rocky]

Dan, I believe you are right.. I was looking into a 1/2 inch sender for my 65" Coronet. Non of the 65 stuff I found had the return, but when I was looking one up for VegasMike I Figured on tapping the tank for a 1/2 inch return. Now I can't remember what is on his 68!!   


At any rate, it is rather easy to remove the 1/4" tube and replace it with 1/2". A cut off tool, drill and a bit of grazing. If you can't braze it in you can take it to a radiator shop and have it done pretty cheap.. 

I can't think of any reason anyone would need anything larger than a 1/4" return line.  The return is smaller for a reason.  The fluid will take the path of least resistance, and you would actually be starving your carb if you used the same size for supply and return.

[Steve P.]

[

I can't think of any reason anyone would need anything larger than a 1/4" return line.  The return is smaller for a reason.  The fluid will take the path of least resistance, and you would actually be starving your carb if you used the same size for supply and return.

Regulators built with a RETURN port direct fuel flow to the fuel line ports. What ever fuel is not needed by the carb is then directed to the return port. This is exactly the way your EFI daily driver works.  Go back and look at the BG site I posted or go to Holley or any other fuel pump company's site. They all recommend a larger or equal size return line as the biggest feed line..   The reason for the larger return line is to have little or less pressure on the return system.

Return lines ARE NOT a mandatory part of the system. Many of our old cars did NOT have them at all. That doesn't mean that foreword progress isn't a good thing. Model A's didn't have heat. Hell, the first cars didn't have windows!!   How about those disc brakes??  Haha... 

Another thing to keep in mind is that the cars we are all working on did not come with expensive electric fuel pimps.. Electric fuel pumps are designed to move fluid up hill, so to speak. They realllly don't like to spin without moving fluid. When they do they will heat up and cause early failure.  The pump companies don't tell you this with a big red warning tag as they want to continue selling pumps..  Much the same as headliner glue..  6 - 7 years and the glue quits holding it up.. (CRAP, time for a new car)!!

[deputycrawford]

     I have a much simpler post dealing with just the original question. My two cents would be to go to the loacl NAPA dealer and look through the back of their fuel filter book, as I did. I found a filter that had 3/8" in and out with no return line. It was around $7-$10. I did end up getting the return style and ran a 1/4" line to the tank. I also have the 1/2" sender in my tank which has the 1/4" return line built in. It as easy as running the line and hooking it up.
     Oh, I needed my return installed because I have a mechanical pump and was having vapor lock problems. A 1/2" phenolic spacer helped but it didn't fully disappear until I added the return line. I know its not manditory for a return on and electric pump but keeping the fuel moving away from the under hood heat and exhaust heat might be beneficial. Just my experience.

[Rocky]

Regulators built with a RETURN port direct fuel flow to the fuel line ports. What ever fuel is not needed by the carb is then directed to the return port. This is exactly the way your EFI daily driver works.  Go back and look at the BG site I posted or go to Holley or any other fuel pump company's site. They all recommend a larger or equal size return line as the biggest feed line..   The reason for the larger return line is to have little or less pressure on the return system.

Steve, I took your advice and looked up the Holley site for the Blue pump application.  Here are the instructions.  http://www.holley.com/data/Products/Technical/199R7914-3.pdf

The regulator is a NON-return style.  They also suggest a 3/8" fuel line.  1/2" is not reccomended under 750HP.  I also looked at my EFI daily driver, a 98 Neon R/T.  It doesn't have a return line either.  I was just trying to save the guy some time and money.  He should be fine using what he has already.  Your advice is great you know your stuff; however, I think it is major overkill for this application.   

[Nacho-RT74]

in your opinion... if I finally go with 451 stroker not for race but street...  can I keep the stock 400 fuel lines and will I need a return line ?

[Rolling_Thunder]

I will be running a return line for the EFI ---