Any reason NOT to upgrade to 3/8 fuel line?

[1974dodgecharger]

I have a mild build on a 383 and I have decided to take apart the fuel line, tank, etc.. a total replacment.  Originally it has a 5/16 line with no return. 

Would it hurt to just upgrade everything to 3/8 with a return line/vapor setup?

[Fred]

Won't do any harm at all. In fact, in my opinion, it's a good idea. I myself have got a 3/8 fuel line but no vapour return line, I just plugged up the vapour return plug on the sending unit.

[1974dodgecharger]

Won't do any harm at all. In fact, in my opinion, it's a good idea. I myself have got a 3/8 fuel line but no vapour return line, I just plugged up the vapour return plug on the sending unit.

hmm...interesting I guess I could do that also never thought of it and when i do drop the hemi in I could then re-route another line to the vapor unit.

[Fred]

Yes you can but I've got a hemi in mine and run it without the vapour return line. And I have no issues.

[1974dodgecharger]

no vapor lock issues fred or any of the sort?  No starvations of fuel in higher rpms?  I was reading on the separator and thats why it was required on the 426/440 setup was that during higher rpms the engine would starve and the vapor fixed this. 

[Fred]

No problems what so ever. My hemi is a 472 and I fitted a B/RB-HEMI fuel pump. But I did mount a heat shield under the manifold so the carby is protected from engine heat. I run it on hot summer days (this is Australia lol) and have never had any issues with fuel supply to the carby.

[flyinlow]

 What is your max. fuel flow or worst gas millage?

4 MPG at WOT?   Burning 1/2 gallon per minute.  Does your current set up deliver that?

[1974dodgecharger]

What is your max. fuel flow or worst gas millage?

4 MPG at WOT?   Burning 1/2 gallon per minute.  Does your current set up deliver that?

i get roughly 8mpg thats alot of heavy foot which i do when i acceralate onto highway.

[Fred]

I average around the same. 

[1974dodgecharger]

I average around the same. 

and yet you have a nice hemi vs my 383 im still savin for a crate 426 myself...


why do you ask flyinlow what my mpg is?

[Dino]

Now correct me if I'm wrong, but is the return line that goes with the 3/8" inlet line only 1/4"?  Should the return line not be the same size or bigger than the inlet line?  I suppose it's a moot point seeing that the connection on the sending unit is for a 1/4" line.

I also have the 5/16" line only and am looking to upgrade, I have the canister waiting to be put in place.  Who provides the best lines and clips btw? (quality, cost, good company to order from).  Has anyone installed a sending unit without the special tool or is it a must have?

[flyinlow]

What is your max. fuel flow or worst gas millage?

4 MPG at WOT?   Burning 1/2 gallon per minute.  Does your current set up deliver that?

i get roughly 8mpg thats alot of heavy foot which i do when i acceralate onto highway.

Plumb a fuel pressure gauge in and see if your 5/16 line holds pressure going from 0-120 mph.  I switched to 3/8's

The only advantage a 5/16 system might have is the fuel near the engine would have less exposure to heat before getting to the carb. Smaller surface area on the pipe and the fuel goes thru faster. 

[green69rt]

Now correct me if I'm wrong, but is the return line that goes with the 3/8" inlet line only 1/4"?  Should the return line not be the same size or bigger than the inlet line?  I suppose it's a moot point seeing that the connection on the sending unit is for a 1/4" line.

The vapor separator has an .060 orifice ( I think that's the size??) in the vapor return line nipple, so even a 1/4 inch return is over sized.  You don't want to bleed all your fuel pump pressure back to the gas tank or you would starve the carb.

[flyinlow]

I
why do you ask flyinlow what my mpg is?

I was not interested in your average mpg. I was interested in you WOT mpg.  Average Auto engine fuel burn per HP .4-.5 pounds per hour . Assuming your engine makes 400HP.

400hp X .5 = 200 lbs. per hour  divided by 7.5 lbs. per gal. = 26.67 gallons per hour.  Your fuel system needs to deliver 1/2 gallon per minute to drive around a Nascar track at WOT.

I got these numbers from the internet, so they must be true.  

[1974dodgecharger]

i was reading thats the reason to do a return line so the engine does not starve of fuel it moves the fuel faster? thats why they were only on the 440 and hemi i believe?

i only plan to do this since im i have the whole tank taken apart anyways and plan to redo the whole lines if nit at least get the 3/8 tube in the fuel sending unit in and upgrade the lines later for a hemi.

Now correct me if I'm wrong, but is the return line that goes with the 3/8" inlet line only 1/4"?  Should the return line not be the same size or bigger than the inlet line?  I suppose it's a moot point seeing that the connection on the sending unit is for a 1/4" line.

The vapor separator has an .060 orifice ( I think that's the size??) in the vapor return line nipple, so even a 1/4 inch return is over sized.  You don't want to bleed all your fuel pump pressure back to the gas tank or you would starve the carb.

[1974dodgecharger]

holy crap you are corrent on the hp rating wow thats really good man based on the fuel consumption you have.

im impressed.......wheres this formula on the net? 

I
why do you ask flyinlow what my mpg is?

I was not interested in your average mpg. I was interested in you WOT mpg.  Average Auto engine fuel burn per HP .4-.5 pounds per hour . Assuming your engine makes 400HP.

400hp X .5 = 200 lbs. per hour  divided by 7.5 lbs. per gal. = 26.67 gallons per hour.  Your fuel system needs to deliver 1/2 gallon per minute to drive around a Nascar track at WOT.

I got these numbers from the internet, so they must be true.   

[green69rt]

i was reading thats the reason to do a return line so the engine does not starve of fuel it moves the fuel faster? thats why they were only on the 440 and hemi i believe?

i only plan to do this since im i have the whole tank taken apart anyways and plan to redo the whole lines if nit at least get the 3/8 tube in the fuel sending unit in and upgrade the lines later for a hemi.

Now correct me if I'm wrong, but is the return line that goes with the 3/8" inlet line only 1/4"?  Should the return line not be the same size or bigger than the inlet line?  I suppose it's a moot point seeing that the connection on the sending unit is for a 1/4" line.

The vapor separator has an .060 orifice ( I think that's the size??) in the vapor return line nipple, so even a 1/4 inch return is over sized.  You don't want to bleed all your fuel pump pressure back to the gas tank or you would starve the carb.

Maybe, but a 0.060 oriface won't flow a lot of gas, but it will flow a lot of vapor.  So. will there be liquid gas in the return line?  Probably because there should not be a lot of vapor in the gas pump discharge line but I don't think it would be significant compared to the total discharge flow from the pump.  Per this thread... alot of folks have done away with the seperator with no ill effects so I think it is just a safety precaution that MOPAR added because of some calculation somewhere that said "vapor could get into the carb and do bad things."  But if vapor makes it to the carb isn't there a float bowl vent??  But if you want a correct setup you need the line and I can't think of anything it would hurt to have it in

[Fred]

I average around the same. 

and yet you have a nice hemi vs my 383 im still savin for a crate 426 myself...

I had mine custom built.     If you do get a crate hemi, pull it to bits and have everything checked. 

[Fred]

Now correct me if I'm wrong, but is the return line that goes with the 3/8" inlet line only 1/4"?  Should the return line not be the same size or bigger than the inlet line?  I suppose it's a moot point seeing that the connection on the sending unit is for a 1/4" line.

I also have the 5/16" line only and am looking to upgrade, I have the canister waiting to be put in place.  Who provides the best lines and clips btw? (quality, cost, good company to order from).  Has anyone installed a sending unit without the special tool or is it a must have?

No Dino, the return line doesn't have to be bigger than 1/4". The fitting on the sending unit is only 1/4".  Bigger is not always better.