Fuel lines, hard or soft. What is the general sense on fuel lines?

3/8 steel with NPT brass ends. Took me 3 tries before I got the bends right, had to buy a length for each try. I bought a trick tube bender but I looked all over the store and couldn't find a tube straightenerou:

 

Not a real fan of NPT brass fittings for high performance. The 90 degree fittings are very restrictive.

 

Didn't use any 90 degree fittings... I have a tube bender.
Actually, now that I think about it... the fittings that came on the tube were steel double-bubble flares, not brass NPT, but I did use a brass NPTadapter because the input threads in the chrome fuel-line (with the built-in port for a fuel pressure gauge) were NPT. The chrome fuel-line also had a 90 degree banjo fitting at the carb.

 

I always straighten messed up tubes with a 5 pound hammer (also good for fixing computers.):idea2:

 

Id be using as few fittings as possiable.
Normal brass NPT ones and no 90* bend adapters. All straight stuff.

Not a fan of the AN fitting stuff, cost way to much for what it is.

Though I never used aluminum tubing like that and only worry about the softness?

Even with a tubing bender is it gonna kink easy and what about making the flares? I can see it splitting when the flare is made, copper does sometimes.
I got a good flare tool. But dunno how manytimes I had to re-do the copper line for my air compressor as the flare would crack.

 

Here's where I go OVERKILL. If you say a fuel system should be good for 500hp, I want one good for 1000hp. In the early days of hot rodding where we were swaping engines into anything that had been 4 and 6 cylinders with 1/4" and 5/16" lines, I learned early to GO Big, keep the lines away from HEAT and have as much pressure as the needle and seat will stand. You wouold be surprised at the cars I beat that had lots more "good" parts and should have been faster, but while they were running out of fuel, I would drive right by for the win. I know you street guys have to deal with things that a race car don't but don't sell your self short. Note: a car with gears, that 60's real well has to have the pressure (pump in rear) or vacuum (stock pump) to over come the fuel wanting to go in the other direction in the line.
Jim N.

 

well shoot man, what are building with 500 hp? i live close. i wanna see!!:3gears: :3gears: gimmme a holla, bro

 

Ok Im sorry I was exploring using NPT fittings from hardware store, as I won't need fittings but for the ends of the hard line for adapters for the steel braided rubber. So my plan is to use simple NPT air fittings stuff as they got nice nipple adapters I can use off the shelf.

Only if I remade a new FP to carb will I need to find that finer thread me thinks???

 

There are different ways to skin that cat. Newer vehicles come with hard plastic tubing; and that can work well. Older vehicles almost universally have double-wall seamless steel tubing--and those two methods are what I'd suggest.

The big factors here are:
1. HOW MUCH horsepower
2. Pusher or "puller" fuel pump?

Amount of fuel needed is directly dependent on horsepower created. And while there's math formulas and such that can get you closer--the fast 'n' easy way is to just move the decimal point:
500 horsepower requires "about" 50 gallons per hour of fuel AT THE CARB OR INJECTORS and AT THE PRESSURE REQUIRED by the rest of the fuel system.

400 horsepower would need 40 gallons per hour. 300 horsepower would need 30 gallons per hour. You get the idea.

Now, if you plan to return fuel to the tank via a return system--the amount returned would add to the amount actually used; and the gallons-per-hour required by the pump goes up accordingly.

The engine mounted fuel pumps have to "suck" fuel through fifteen feet or more of tubing. The tubing needs to be larger than if you have a rear-mounted fuel pump that can "push" the fuel; and doubly so when the rear mounted fuel pump is higher-pressure with a regulator in the engine compartment.

So: I bet you'd have no problem feeding 500 horsepower with stock tubing provided you have a rear mounted pump at ~14 psi feeding an engine-compartment-mounted dead-head (no return system) regulator that provides ~5--6 psi to the carb(s).

As little "soft" hose as possible. 12" is a good figure. ANY "rubber" hose is succeptable to chemical deterioration due to gasoline or gasoline additives. Watch it closely. My friend burnt up his Impala--and nearly his house--because his steel-braid-over-rubber hose rotted away on him in about two or three years; the hose was on the pressure side of the pump, and the electric fuel pump continued to pump fuel through the ruptured hose feeding the fire.

HIGH QUALITY rubber is fine in short lengths. You should NOT use typical rubber hose on the PRESSURE side of the fuel pump!

I'm REMOVING all the steel-braid-over-rubber-liner hose from my boat; and I wouldn't add that to any of my cars; although lots of people do. It's expensive, heavy, expensive, often porous enough so that the garage smells of gasoline after the car has been parked overnight, expensive, and the steel braid will act like a hacksaw on everything it rubs against. It's expensive, and it has a relatively short service life--so you're going to have to replace it much more often than you would replace steel tubing. And it's expensive.

Even more expensive than steel braid over rubber. BUT, it's not porous. It is very sensitive to being curved or bent too sharply--the teflon liner will kink, and then the hose is ruined. Be VERY careful with minimum bend radius!!! This is what is going into my boat; although of the five fuel hoses that are on the boat now, three of them will become steel tubing and only two will remain as "hose".

Huh???

Now you're talking. Of course you need some hose to allow engine movement and to connect to the fuel tank--but the amount of hose should be minimized and then use as much metal tubing as practical.

NO! Copper tubing as sold in the USA will work harden and crack. I'm told that copper tubing available in England has a very thick wall and can be used for fuel plumbing--but--I haven't verified that. It's just what I was told by some guy in England.

Commonly sold for race vehicles. I don't like it; but I can see being forced to used it because double-wall seamless steel tube isn't readily available in sizes larger than 3/8. Not my first choice.

Galvanizing is just zinc-plating; I suspect you mean galvanized steel. Typically "pipe" not tubing. Again, not my first choice. Very heavy, extremely difficult to bend. Typically joined with pipe thread; and that isn't optimum either. Stay away from galvanized pipe.

Somewhat popular. Expensive. Durable. Tougher to form and flare; some folks have problems getting the flares to seal. Plain ol' steel tubing is plenty durable; I just don't see the need for stainless fuel tubing.

Yeah, that works well. I might prefer AN in steel rather than aluminum; but either one can work just fine. Don't confuse "AN" stuff (37 degree flare) with household-plumbing and farm fittings that have a 45 degree flare. Not many hose ends can be used on both 37 degree and 45 degree flares--although there are a few. Otherwise, you'll have cracked female flares and big leaks.

NPT is never used to connect tubing. It is sometimes used to install a fitting into a casting, where the other end of the fitting has a flare or compression ferrule that attaches to the tubing. It should be avoided if possible. Sometimes it's not possible because the other fuel system components like the fuel pump or regulator are already machined for NPT; and then NPT if assembled properly can be just fine. I prefer DOUBLE-FLARE fittings in brass; although I have used compression fittings. Compression fittings WHEN ASSEMBLED PROPERLY can work just fine. They are not as "foolproof" as a double flare; which is why the OEMs used double flare and not compression fittings.

Not if you have any choice about it. But again, sometimes there isn't a choice because other components of the fuel system are intended for plain ol' clamped hose. At least use "fuel injection" clamps rather than worm-gear clamps. Don't confuse this with modern "Push-Lock" hose that is specially-designed to slide over matching hose-barb ends; that stuff is wonderful. Most all the advantages of "quality" steel-braid-over-rubber; but less expensive. May or may not still be somewhat porous. Has a shorter service life than steel tube. It works as well as steel-braid over rubber, at lower cost.

YES! Although modern cars are using hard plastic and that can be just fine, too. I'm considering hard plastic for the boat; but at this point I think steel braid over Teflon is more likely.

Yes! I also have the Mastercool hydraulic flaring tool. Still need to order the 37 degree AN flaring accessories, though.

Yup. Much less expensive and less restriction to bend the tubing and use straight fittings if possible. Sometimes it's not possible; and then you do what you have to.

A good bender will not kink the tubing.

Double-wall seamless steel tubing will not crack at the flare if the flaring tool is used properly. Can't say about copper flares; I usually solder copper tube or use compression fittings

 

Sorry again Jason my brain always goes right the the pipe section.
Though Im sure I can get the proper kind still local.

I just recently dumped my return line system, try to help cure this.
Thinking my FP was just old and worn out I decided to put on a new non-ac FP. which has no return. I don't have AC anymore.

Not a fan or have luck with compression fittings.
Our kitchen sink is using half of my top radiator hose cause of that.

 

Im just planning ahead, your way beyond where I will be anytime soon engine wise. I need to come over n watch you work.

1. Need to square away fuel system so I can enjoy the new trans, instake, carb, ign system as is, haven't been able to go all out and test changes.

2. Then install posi.

3. Then heads n cam, stay low comp.

4. Then turbo's

5. ?

6. Profit

 

dude, im not THAT far ahead. took 2 yrs to do the build on my car,and of course still never done.would definitly have gone with bigger cam. hey, im jobless, so ill pm you with number. get ahold of me.john

 

OK Im back to using 3/8" steel line as after looking at all Ill need, ill be steping down the sizes all over the place.

Only $150-200 150GPH electric fuel pump have a 3/8" fitting though.

All the rest are 1/8" or 1/4" .
All the Mr gasket ones in my needs range are 1/8", knock off off brand is 1/4"

FP regulators are 3/8" though.

Fuel filter 3/8"


I should have no trouble with a 30 GPH 2-4 PSI electric pump as a pusher to feed the Mech stock pump on the block right???

 

I know lots of questions. [ I fixed that post above Jason ]


Would I be better off going back to an AC FP that has the built in regulator and return line to make sure I don't over psi the carb that way?

Or use an external regulator like a 7-9 one and run a return off it.

Or piss on a regulator and return, and just get a gauge installed then decide?


Trying to map it all out on paper first.

 

Probably wise.

Are you talking about PIPE THREAD? 3/8 pipe thread is HUGE.

Pipe is measured by INSIDE diameter; and generally has a thick wall.
Tubing is measured by OUTSIDE diameter, and generally has a thin wall.

3/8 pipe thread is about three times the size of 3/8 tubing.

Ummm...yeah, that'd be fine if you have less than 300 horsepower. And only then if the rating is for 30 GPH at 4 psi and not 30 gph free-flow.

Better Idea: Get a pump that'll throw 50--60+ GPH AT 5--6 psi; and ditch the engine mounted pump altogether. Use QUALITY hose at the engine-to-frame junction; that hose is now under pressure instead of vacuum like with the engine-mounted pump. If it leaks--it's a disaster.

Return system or dead-head--either one works. Return systems cost a lot more, but are said to be quieter and longer-lasting. I have a dead-head system on my "toy" car.

7--9 psi is probably too high, especially for a Q-Jet. 9 psi may be too high for most any carb.

Actually knowing your fuel pressure--at max RPM and WFO--is always a good thing. But in the end...

How...Much...Horsepower???

A Holley Red pump is inexpensive and requires no regulator for most applications. Probably good to 350--400 horsepower. Claimed output is 67 gallons per hour at 5 psi--if you had no restriction in your fuel plumbing, that'd support a BUNCH of power--but--there's always some restriction.

A Holley Blue pump is "somewhat" more expensive; comes with a dead-head regulator, and would probably support in excess of 500 HP because the higher pressure could overcome some amount of restriction in your plumbing.

http://www.holley.com/data/Products/Technical/199R7914-3.pdf

Both of those pumps are NOISY AS HELL; it's the only drawback to them that I know about. Some folks have issues with durability; mine's worked fine for ten years but not many miles. If I were buying a new pump, I'd look at the Holley "Volumax" line; the gearotor pump is said to be much quieter than the vane-style pump--but also more expensive and requires a separate regulator that isn't included with the pump.

http://www.holley.com/data/Products/Technical/Fuel Pump Tech Info.pdf

 

I took another look at this statement.

Do you mean a standard, engine mounted fuel pump with a return fitting leading to 1/4" tubing?

Those return fittings have NOTHING to do with regulating pressure. They're restricted inside so that they're very good at venting vapor, but not-so-good at passing liquid fuel. The ordinary return system on those old cars is a "fix" for vapor lock--NOT a pressure regulation device.

 

My return line carried fuel all right, even before any problems.
Not allot but enough. It would piss out a nice dribble when running but not enough to get your attention or notice fuel loss. But it done that well before any problems.

Back to other stuff.

I was asking about that small electric fuel pump as it will just be a pusher / helper. I got a brand new good block pump that should be able to feed the engine just fine. I just wanted to give it a hand with a small cheap pump that wouldn't over drive it since it sucking fuel from 18ft away. I don't need a $150 pump yet as Id have to go blue as to many bad stories on the web about the red.

 

Yup. Exactly right. Restriction in the return fitting--like jamming a Holley Jet into the tube. Air/vapor passes just fine, liquid fuel gets through too, but not so much as if there were no restriction--you'd be flooded with fuel.

The engine mounted pump probably moves 35--45 GPH. I think you'd want at least that much capacity at the back, or the engine mounted pump will outpace the electric. Then the electric pump becomes a restriction.

By the time you do that--you might as well just use the rear mounted pump and forget the engine-mounted unit.

But maybe I'm mistaken. Never tried to run a rear electric assisting an engine-mounted pump.