3/8 or 5/16 Lines

[Steve P.]

A simple and basic rule of thumb is==  The more CFM your motor requires, the more fuel it requires.

The last thing you want to do is go lean..

[Ghoste]

Mmmm, I could be wrong too, I very frequently am, but I'm pretty sure the 3/8 fuel lines were only used for the Hemi and 440.

[Steve P.]

Looks like all the sending units I'm finding for a Charger are 3/8.  I would think it would have 3/8 being a BB car.  Could be wrong.

If you are looking to replace the unit and lines, just go to the 3/8 and don't worry about it. A bigger line will not hurt anything...

[73ChargerSE]

New lines are far along the line(no pun intended) for me.  I was just wondering and this seemed like a good topic to add it in.

[Purple440]

Well I'm happy with my 3/8 lines and HV 120 Carter.  I don't have a high rpm 440 but my plugs look better (probably because of the pump) and I can check fuel lines off my list of why I'm running lean.  Just checked and my plugs are grey as apposed to white like they were last summer. 

Although my new 120 carter pump has a 5/16 inlet so I'm not sure if that's bad or not since my lines and sender are now 3/8.

- Doug

[Ghoste]

It's definitely a choke point.

[Steve P.]

A point that is commonly overlooked is WHEN to check plugs. 90% of the time we are driving like normal. If you pull your plugs and read them after a normal run to the store and back and they look good, well many are pleased with that. It does not end there......  You also need to know what is going on with your fuel when doing an all out run for the money. IE, do a 1/4 mile blast and at the end of the 1/4 mile shut off the engine and read your plugs..   Most times when I have asked people how they check plug readings they tell me, (I check them after a run to the store). or (I do a 1/4 mile blast and drive right home to check the plugs)..

WELL,,, if you do a big blast and the drive it like grandma you are NOT going to find out anything different than the same drive to the store..  To get it right you have to shut it down at the end of the blast and read the plugs. This is where many people find out they are running lean. Can be due to jetting. Can be due to a fuel system that is not up to the task.

Also keep in mind that a motor on a dyno in not in motion. Dyno's are great for getting your jetting right, but their fuel system is short with very few if any bends and has no G forces working against them. They are also normally in a 70* or so room. The fuel in the bowls is not being sloshed to the rear.  This is an area where fuel injection is king.  Fuel injection is always being scrutinized and adjusted by the computer. It runs more than enough pressure from the pump in the tank to overcome "G" forces. Is always recirculating and is manipulated by the computer for every condition...

Had Team Charger had fuel injection in place during the BULL RUN on Spike they would have come home with $200K....

[Purple440]

I was told that there weren't any 3/8 size carter pumps available so 5/16 is what we had for a choice. 

Good point Steve P.  I'm keep that in mind.

[Steve P.]

This pump and filter makes for an expensive system. I am merely showing this so that some of our younger crowd can see what a common high HP system uses and how it works.

There are many variables in fuel systems. This is just the one I find closest to perfect in my humble opinion..


http://www.barrygrant.com/images/bgfuel/catalog/BG220LINcopy.jpg


Holley used to have a very similar pic. on the www. I just found this first..

[Ghoste]

I was told that there weren't any 3/8 size carter pumps available so 5/16 is what we had for a choice. 

For a stock application perhaps, ask about a Hemi fuel pump.

[Steve P.]

I would think having a bigger supply than the pump can outlet would be a good thing.  If you look at most PUMPED systems they have a large supply. Then a pump and the return is aways bigger yet or at least equal to the supply.   Simple hydraulics 101.. A/C works this way as does your power steering.

[Charger1973]

I agree with Ron that a 5/16 line can keep with your motor, but I prefer a very large line with a regulator and return line to the tank. This becomes more of a necessity with higher HP and in hotter areas of the country. With the excess fuel being returned to the fuel tank you stand less of a chance of vapor lock as the fuel normally stays cooler. You will have plenty of fuel at the ready with the larger line. You will also work the fuel pump less hard with a by-pass. Mechanical or electric pump. 

There are many trains of thought on this subject, but every HIPO manufacturer will tell you bigger is better and return lines are a big plus. 

Ask VegasMike about high temps without a return line..

How would I go about setting up a return line to the tank?  Im not sure how that works. 

[Steve P.]

Look at how this is run for a general idea.

http://www.barrygrant.com/images/bgfuel/catalog/BG220LINcopy.jpg


What I plan to do is weld a return nipple into my stock tank. I will feed my carb using an electric fuel pump and 3/8 line. Then close to the carb I will run a by-pass style regulator. From there I will run a 1/2 inch return line back to the tank..

I live in a hot climate and have plans for a big future build..

[Charger1973]

Looks fairly simple.  I saved that picture for future reference, it's not one of those things im going to do right away but I like the idea...   

[471_Magnum]

A 440 HP is 3/8" from tank to pump, then 5/16" from pump to carb.

[darrin75]

I said what the hell. New Hp pump, and new sending and new 3/8 fuel line?  Bigger can only help.

[Purple440]

same here

[Steve P.]

Yes, your suction and return should always be larger than the pressure line..

Some pumps have a by-pass built right into them. That's ok.. I prefer the by=pass being AFTER the carb feed lines with a return.  Plus living in a high humidity area like I do in Florida, I want as much gas being circulated and filtered as possible..