3/8 or 5/16 Lines

[darrin75]

383 Engine
750 Holley carb
452 heads
509 cam and lifters

I have 5/16 sender and fuel line. My questions are, Is this enough fuel line for this set-up, should I go to the 3/8 set? It Seems that my car wants more fuel, although It is a fresh rebuild and has not been really broke in yet. Any advantages to going with the 3/8 set up over stock 5/16 lines and sender. The 5/16 is what was in the car when It had a 318 in it. Am I getting enough fuel. Also Who recommends electric fuel pump over manual pump? Any great upgrade there? Thanks

[gtx6970]

depends on the rpm range it's gonna live in

upgrading to 3/8" is not going to hurt it in any way, but may not be needed or worth the costs involved

[Purple440]

darrin75, I'll just share my experience and it might help you decide:

I have a 440, and at one point it was a 5/16 sender and lines, and a stock mechanical pump.  My power died off after about 4500 rpm.  This spring I installed a Carter 120gph pump and 3/8 sender and lines.  With that change alone I got power through 6000rpm so I was very happy.  Regarding the electric pump, I went with another mechanical pump that put out more volume and it was just a simple swap.  With an electric it may take more work/time assuming you have a mechanical now, for maybe no advantage unless your racing.

Maybe it depends on your RPM range.  My cam gives me a range of 2500-6000rpm.

P.S.  My car had a 318 in it also before swapping in the 440.

[firefighter3931]

A 5/16 line with a good quality mechanical pump will support 500hp no problem. In your case i would keep what you have and invest in a high volume Carter mechanical (6psi) street pump. Check the fuel pump pushrod while you're at it.....it should measure 3.25in....if not...replace it when you do the pump. 



Ron

[Purple440]

Ron is that for a 383 and/or 440?  Do you think I would have been ok with 5/16 lines but the HV pump?

[GreenMachine]

5/16" lines are fine for your application, just get a higher volume mech. pump.

[firefighter3931]

Ron is that for a 383 and/or 440?  Do you think I would have been ok with 5/16 lines but the HV pump?

Purple, doesn't matter what engine....in the 500hp range that line is fine. In fact i have a buddy who ran mid 10's with a roller cammed 440 and HV mechanical pump....no problems. Oh ya....the car was originally a 383 with the 5/16 pickup and fuel lines. 


Ron

[Purple440]

I guess I should have asked before I replaced my 5/16...that was a pain in the ass.     Yeah mine was a 383 car too even though I got it with a 318.

Oh well, that's one less thing to do when I put my Roots blower on 

[4cruzin]

I would change it out anyways . . . better too much than too little when it comes to gas flow!   

[Nacho-RT74]

from factory all 440s were 3/8, but I'm agree 5/16 is enough even for a 451 stroke, at least on street use, maybe not race.

I just bought a ne fuel sender 3/4 with 1/4 retunr line. I will plug on my stock 5/16 and just will upgrade the fuel line IF I notice is not enought to my very future 451   VEEERY FUTURE IT SEEMS

[sean68charger]

from factory all 440s were 3/8, but I'm agree 5/16 is enough even for a 451 stroke, at least on street use, maybe not race.

I just bought a ne fuel sender 3/4 with 1/4 retunr line. I will plug on my stock 5/16 and just will upgrade the fuel line IF I notice is not enought to my very future 451   VEEERY FUTURE IT SEEMS

i disagrre with you that all 440`s came with 3/8. my genunie 68 R/T had 5/16 fuel line, i changed it a few weeks ago and it was the original one i swapped out

[Nacho-RT74]

well... it is what does appear stated on Mopar manual catalog

[Steve P.]

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..

[darrin75]

Best HV mechanical pump? I want more fuel?

http://store.summitracing.com/partdetail.asp?part=CRT%2DM5903P&view=1&N=700+

Also If I got this I assume I need no regulator or gauge, and what fittings do I use for 5/16 line?

[darrin75]

383 Engine
750 Holley carb
452 heads
509 cam and lifters


With these spec should I have the vaccum advance plugged off???

[Ghoste]

Yes.

[Rolling_Thunder]

I had a 5/16" fuel line with a mechanical pump...      with a 383...    starved out at high RPMs...    i didnt like it...    so now im running -10AN and -8AN lines   

[Steve P.]

If you have enough power to pull the front wheels off the ground you better have a good electric pump with large volume and return line.  You know that feeling of being slammed back or pinned into your seat?? Well fuel is no different. While you are being pinned to the seat your fuel is too. It is trying to run back to the tank. Imagine sitting in the passenger seat of your car with someone else driving it. He stands on the go pedal from a dead stop, BUT,,,,,  SOMEONE PULLED YOUR SEAT BOLTS... Where are you going?? 

Standard every day drivers from the factory where never set up for this scenario. Most of the time you can get away with a 'like factory' set up.   You better have big fuel bowls and set up right..  True 1/4 mile cars that starve the motor for fuel lose.. If this wasn't true, (RACE CARS), would never bother with electric pumps and the added cost of the fuel regulator and lines..   

[darrin75]

Ron is that for a 383 and/or 440?  Do you think I would have been ok with 5/16 lines but the HV pump?

Purple, doesn't matter what engine....in the 500hp range that line is fine. In fact i have a buddy who ran mid 10's with a roller cammed 440 and HV mechanical pump....no problems. Oh ya....the car was originally a 383 with the 5/16 pickup and fuel lines. 


Ron

This guy seems to thing I will be fine with this set-up.  He seems to know lot about engine specs.

[Nacho-RT74]

IMHO, don't get a headache about... change in a future JUST IF YOU FEEL that you are needing. But when you need a fuel sender you can start getting a 3/8 fuel sender with return line anyway, will be just a step ahead and price is the same than 5/16 unit. I'm doing it.

[Steve P.]

Ron is that for a 383 and/or 440?  Do you think I would have been ok with 5/16 lines but the HV pump?

Purple, doesn't matter what engine....in the 500hp range that line is fine. In fact i have a buddy who ran mid 10's with a roller cammed 440 and HV mechanical pump....no problems. Oh ya....the car was originally a 383 with the 5/16 pickup and fuel lines. 


Ron

This guy seems to thing I will be fine with this set-up.  He seems to know lot about engine specs.

Ron absolutely know a thing or two about building.. No doubt about it.. There is very, very little that we don't agree upon. If I sound like I don't agree with him I'm sorry. I don't always print what I am thinking.. What I am saying here is that all cases are different. If your building a street cruiser with a fairly healthy motor you can get away with allot. If you go back and read what I have wrote you will see that I am merely pointing out a few points. I don't know your exact build or what your plans are for the future.  Or for that matter where you live, Climate wise.   Also, when asking a question on a board like this many people read it and go back to it for reference. Many others in the past have asked the same question. Many will in the future. I am just making points that you and others can use for consideration for your and their builds.

For instance, I am building a 450+/- hp motor for my 65' Coronet 500. I live in Florida where it is hot and muggy all summer. The motor going in NOW is a light weight, but I am going to set it up with a electric pump, fat lines and a regulator. It's probably over kill for this motor, but I have plans for a big stroker in the future. Also air conditioning. My car is fairly light and holds 4.10 gears RIGHT NOW..  Sure I could save some time and money right now, but I now what will be coming down the line later, so why do it 2 times when I can do it once.  Setting it up the way I am going to now will guarantee plenty of fuel all the time and will continuously be pumping and filtering and keeping fresh fuel all the way to the carb..

You can absolutely trust what Ron tells you. He doesn't plug for anyone unless he has used it or is close to someone he knows well that  has. The info I have given you is a step or two more toward hi horse, full blast runs with just about anything you want to throw at it and in most conditions..

Again, I am at Sea Level and don't need half of the stuff I am doing now. Some are at 4000 ft. above sea level and have shitty gas. (Vegas has shitty gas).....  Also 2300 ft. above sea level. Good place for a strong fuel system. Under 10.5 clicks at the track==== Better have a strong fuel system..  In a hot area that likes to cause problems with vapor lock.. You get the picture... 



This is of course my opinion.

[darrin75]

No maybe you took it the wrong way, I value all the opinions on the board, no problem at all.

[73ChargerSE]

What lines would a 400 '73 have? I'm guessing 3/8?

[Ghoste]

5/16.

[73ChargerSE]

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.

[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..