3/8” Fuel system for an A-body?

[dust]

Did the 340/360 Dusters come with 3/8” fuel lines and pickup/sender assemblies?

I am upgrading my stock /6 Duster fuel system for my street 408. I would like to just go to NAPA and buy an OE style pickup/sender assy.

Also, do you guys get fuel line and bend it or pre-bent fuel lines for you vehicles?

Thanks
-dus

[ehostler]

Allstar or Quanta should have everything that you need to convert to 3/8" fuel lines. They should have the correct pre-bent line.

[racintracy]

I bought my pre bent 3/8 fuel lines and pickup for my 68 Cuda from the Paddock and they fit real good. Not sure if the have them for Dusters but you might check. I also agree with sbfinne about low quality of NAPA lately.

[BillyBob]

IMO, if it is a mainly street driven vehicle 5/16" lines will be adequate. It's your $$$

How much fuel flow is enough?
The correct volume of fuel is that which is required to support the amount of horsepower that the engine can produce. Most engines that are using gasoline burn approximately .5 pounds per horsepower-hour. This is sometimes called BSFC (Brake Specific Fuel Consumption). What this means is that for each horsepower produced, it takes ½ pound of fuel. This is a general statement and sometimes engines can be a little more efficient than .5lb/hp-hr., but it is a good practice to plan and measure fuel system operation using this number. Carburetors must have a stable supply of fuel in order to maintain the correct liquid fuel height. This is most difficult with drag racing vehicles that sometimes have forward acceleration and wheel stand at the same time. Each time that a nitrous system is engaged, additional fuel supply demands must be met or melted parts may result from "system lean-out." The fuel required is in excess of the .5 lb/hp-hr. for normally aspirated conditions. The additional fuel requirements for nitrous system planning is about .7 lb/hp-hr.

How much fuel pressure is necessary?
First, the fuel system pressure (provided by the fuel pump) must be enough to oppose the effects of gravity during the launch and during the run for drag racers. The system pressure of at least 6 to 8 psi per g is "generally" adequate. Fuel regulators need to be adjusted to 6.5 to 7.5 psi WITH FUEL FLOWING at a rate of about ½ cc per second (that's about 10 drops per second). Higher fuel pressure will generate more foam in the float bowl.

Use a handheld calculator and plan on .5 lbs/hp-hr. (gasoline). Methanol alcohol requires about 1.0 lbs/hp-hr. Use .7 lbs/hp-hr when planning a gasoline system for nitrous assist. EXAMPLE: You have a 550 hp engine. 550hp x .5 = 275 lbs/hr. (gasoline). Although you need to know how much your fuel weighs, assume for this example that it weighs 6.2 lbs/gal. 275 lbs/hr. ÷ 6.2 = 44.35 gal/hr. Dividing by 60 (minutes per hour) yields .739 gal/min (GPM). Note that this flow number is what your engine needs at the float bowls.

[pishta]

44.35 gal/hr, bummer~! I can only drive my car WOT for 20 minutes! I bought 15 feet of Copper 3/8 and just bent it up while I was shoving it in the supplied holes I also used the same tubing to create my new pick up on the sending unit. I ground out the 5/16 sender tube and drilled a new hole for the larger tube. I tried to braze it but ended up JB welding it.

[ehostler]

Why did you go with copper over stainless steel fuel line? I thought that the copper would corrode quicker than SS, when exposed to gas and all of it's additives. Also, he intends on converting to ethanol in the future. I don't know that that does to the choice in plumbing materials.

[Ray Bell]

I guess you could avoid replumbing the whole car by having a dump tank under the bonnet?

What I mean is you could run the regular 5/16" line to a half-gallon container mounted on the firewall or inner guard, then run whatever you like from there to the carburettor with no real fitment problems or expense.

After all, it's only for short bursts, right?

[Robertson_Tech]

one other problem with copper tubbing is it may kink when bent. I have bent lots of SS316L tubing it is easy when you get the hang of it and use a bender.

Use a larger feed from tank to rear mounted pump then regulate pressure back down at the fenderwell. It is easer to push liquid than to pull it.
Remember even with good bends each bend adds resistance and with flow pressure drop.

[pishta]

Originally Posted by ehostler

Why did you go with copper over stainless steel fuel line? I thought that the copper would corrode quicker than SS, when exposed to gas and all of it's additives....

Its the sulfer in the gas that corrodes the copper and US gas is Very low in sulfer <.03% mass. You know that neat chrome fuel line that feed the Holley? "The chrome plating of these Mr. Gasket gas lines dresses up your engine bay, along with providing an excellent trail for your fuel to travel. It's made of copper tubing, brass fittings, and silver-brazed connections." I used a jim-dandy tubing bender that made be-u-ti-ful bends in the tubing and a compression fitting (never use water pipe solder, only silver solder when working with any kind of gas line). Hell, im gonna repipe my house next!

[dust]

Originally Posted by Ray Bell

I guess you could avoid replumbing the whole car by having a dump tank under the bonnet?

What I mean is you could run the regular 5/16" line to a half-gallon container mounted on the firewall or inner guard, then run whatever you like from there to the carburettor with no real fitment problems or expense.

After all, it's only for short bursts, right?

My dad was telling me about that, where do I get a tank like that? Is it called a fuel log?

A tank between the pump and carb, right?

Thanks for the replys to far, I'm going to have to re-read BillyBob's post a few times. Yes, I plan on running Ethanol in the future but not for a couple of years.

[Dennis Jokela]

I know for a fact, that my 71 Scamp, has run a best of 11.86 at 114mph with a 5/16 fuel line that had been flattened with a floor jack several years ago. I just replaced the whole system with a cell and 3/8 line. I was quite surprised to find the crushed fuel line.

Dennis Jokela

[pishta]

Originally Posted by dst

My dad was telling me about that, where do I get a tank like that? Is it called a fuel log?

A tank between the pump and carb, right?

I dont know if that would work unless it were above the float level (maybe not). If it were on the frame rail for instance: you gas it, the G's force the fuel in the line to the rear. The "can" is in front of the pump. The pump is trying to push fuel that may not be available into the can so it can displace fuel into the bowls. the bowls have no way to draw up fuel from the can by themselves so you are still in the pickle. If it were above the bowl level, you could run the car without a pump for the entire amount of fuel available in the can. But then you would have to figure out how to vent the can so you could actually fill it up when the carb inlets "seat". Then you would have to figure out how you would stop your fuel pump from filling the can past the vent (like a float valve). Ever seen the filler tank on a Ford 390? Its a small tank about carb level that has a cap on it. that would make a good can with a floating check ball type valve that would plug a vent when the fuel level got to a specific level. Sounds like alot of work. Maybe just try one of these inline before your pump?

[DanL]

If it were my car, I'd get rid of ALL copper fuel lines as soon as I could. Copper work-hardens with vibration and becomes brittle. That means cracks, leaks, and well, you get the picture.

A rule to live by is to never, ever use copper for a fuel line.

[toad490]

Originally Posted by dst

My dad was telling me about that, where do I get a tank like that? Is it called a fuel log?

A tank between the pump and carb, right?

You could use a surge tank from a race radiator, there're sealed and usually have AN fittings. You can pick used ones up preety cheap and they look good. Look them up on eBay its a good place to see whats availabe. Fuel logs are generaly a fitting for double pumper carbs.

[toad490]

Originally Posted by pishta

Iavailable in the can. But then you would have to figure out how to vent the can so you could actually fill it up when the carb inlets "seat". Then you would have to figure out how you would stop your fuel pump from filling the can past the vent (like a float valve). Ever seen the filler tank on a Ford 390? Its a small tank about carb level that has a cap on it. that would make a good can with a floating check ball type valve that would plug a vent when the fuel level got to a specific level. Sounds like alot of work. Maybe just try one of these inline before your pump?

I just had a thought, what about a oil accumulator? I have a 2 quart one that I was going to use in a marine application. It would of supplied oil to the engine incase the pickup got uncovered in rough weather. It could be plumbed into the fuel line inbetween the pump and carb and before the regulator. You would have 1 1/2 or more quarts of fuel stored under pressure. Sound too simple to actually work.

[BillyBob]

His question was:

"Did the 340/360 Dusters come with 3/8” fuel lines and pickup/sender assemblies?

I am upgrading my stock /6 Duster fuel system for my street 408. I would like to just go to NAPA and buy an OE style pickup/sender assy."

My answer is no, they did not come with 3/8" fuel lines and pickup/sender.



Furthermore, what MOPAR factory standard production car(other than special units) had larger than 5/16" tubing? [circa 1950-1980]

Is going larger than the stock size better or necessary? Maybe..........

[pishta]

Originally Posted by DanL

If it were my car, I'd get rid of ALL copper fuel lines as soon as I could. Copper work-hardens with vibration and becomes brittle. That means cracks, leaks, and well, you get the picture.

A rule to live by is to never, ever use copper for a fuel line.

Thanks for the concern, Dan. All my copper is either clipped to the frame (tank to pump) , or through brackets wrapped in thin split foam pipe insulation. Since my motor is solid mounted and I used stainless braided hose from the fender mounted filter to the carb I dont think anything is going to vibrate work harden in its 100 mile a year lifetime.

[pishta]

An accumulator would have too much pressure behind it. If you could knock down the pressure to about 6, it may work, but you would have trouble filling it with stock pump.

[dust]

Originally Posted by BillyBob

Furthermore, what MOPAR factory standard production car(other than special units) had larger than 5/16" tubing? [circa 1950-1980]

Thats a good question, I wonder what engines came with 3/8". Did any of the 383 or 400's come with 3/8"?

[dust]

Other than pishta, anybody else bend their own lines?

[DanL]

Originally Posted by toad490

I just had a thought, what about a oil accumulator? I have a 2 quart one that I was going to use in a marine application. It would of supplied oil to the engine incase the pickup got uncovered in rough weather. It could be plumbed into the fuel line inbetween the pump and carb and before the regulator. You would have 1 1/2 or more quarts of fuel stored under pressure. Sound too simple to actually work.

Not sure how your oil accumulator is built, it might be OK. But just a can, by itself, in the fuel line wouldn't help at all. It would just be a large piece of fuel line. Now, if it has a diaphragm in it, and you could put a little air or nitrogen pressure (4-6 psi) against it, it would do the trick.

Look at it this way. If your carb is starving for fuel, just having that extra volume in the line won't help at all, because the problem is the fuel pump is unable to supply enough fuel for the carb. But, if you had an accumulator (with air pressure), it would then supply the fuel during the time the fuel pump is unable to keep up. When the demand goes back down, the pump can again pressurize the accumulator.

In the end, though, I agree with BillyBob. I think 5/16" line is plenty adequate for most street-driven cars, probably up to 400 HP or more. There might be other reasons for making the switch, though. For instance, the lines on my 73 need to be replaced because of corrosion and damage. I'm going to switch to 3/8" line for 2 reasons; 1) it will ease the plumbing adaptation problems with my Holley EFI fuel pump, which is designed for 3/8 lines, and 2) some day, it might have a bigger motor . So, if you need to replace the lines for other reasons, go for the bigger ones.

Pishta; 100 miles a year isn't much, perhaps you don't need to worry. I still wouldn't trust copper for my fuel lines, but maybe that's the jet mechanic in me being too cautious. The vibration doesn't have to be the copper lines actually flexing around, although that certainly speeds the process. Just the vibration from your solidly mounted engine would concern me, because all those engine vibrations go directly into the chassis rather than being absorbed by rubber mounts.

Edit: Of course, I meant 3/8" lines, not 3/16.....

[Robertson_Tech]

Originally Posted by dst

Other than pishta, anybody else bend their own lines?

I have bent lots of lines fuel lines, brake lines with flared ends and lots and lots of 1/4 and 3/8 316L SS toxic gas lines, it takes a little pratice to get the hang of a tubing bender but then it is easy...

[rusty duster]

I don't think that a tank above the carb is safe and is not allowed in NHRA .

[ehostler]

Originally Posted by BillyBob

Furthermore, what MOPAR factory standard production car(other than special units) had larger than 5/16" tubing? [circa 1950-1980]

440 6 packs and Hemis had the 3/8" fuel line.

I've run a pretty stout 383 on 5/16" with an electric fuel pump and had no indications of fuel starvation.