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  #1  
Old 01-01-2003, 11:52 PM
dans76sport dans76sport is offline
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Default fuel line size

does any one else out there wonder if the 5/16 line from the tank to the fuel pump is too small? I have been considering changing this to 3/8 but wonder if it is gonna help at all. I run a 350 to 400 horse 360. Bracket racer, with some street use. Carter mechanical pump and holley 750. what do you all think?
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  #2  
Old 01-02-2003, 12:37 AM
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340MAN 340MAN is offline
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You can be to small & are with 5/16 line, but you stand to run -10an line. Now if you are trying to stay with original style lines then I believe that is the largest line without going aluminum.
A -10an line is very near 1/2" od - a little larger than 3/8 id.
This will give you room to move up the h.p. with redoing the fuel system when your ready.
Just my thoughts
Good luck
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  #3  
Old 01-02-2003, 01:27 PM
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Does your fuel pressure drop at WOT?
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  #4  
Old 01-03-2003, 03:21 AM
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Default Agree

-10 is correct application up to about 800 HP Gas / 1200 HP Alcohol.

Give that Carter what is wants!!!
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  #5  
Old 01-03-2003, 11:12 PM
451Mopar 451Mopar is offline
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3/8" line should work fine.
#10 AN is way too big, I think 340MAN means #8 AN which is just a tad smaller than 1/2" ID and is usually good for 600HP? The #10 AN would be pretty hard to plumb because of it's size, also braided AN hose is expensive.
If your car is a street car, you can get pre-bent 3/8" steel line from fine lines or one of the other places that reproduce factory fuel lines. These fit really good and may cost less than braided AN lines. You will have to enlarge the fuel line pickup in the gas tank to get the full benifit of the larger lines. If your car had the option of the 1/4" vapor return line, it would be worth using it too with some type of vapor by-pass to prevent vapor lock in hot weather.

In my opinion the 3/8" line is probbably good for 500HP?
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Old 01-04-2003, 12:11 PM
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"In my opinion the 3/8" line is probbably good for 500HP?"

In my opinion the 3/8" line is probbably good for 400HP?

5/16 is OK for a /6 or stock 318 anything over that and you need bigger lines and a bigger fuel pump. Beware of inline fuel filters..most are designed for 5/16 fuel lines and you can run -16 but you'll still flow at 5/16 volume trying to force the fuel through those cheezy filters.

My guess is that probably 75% of all modified Muscle cars don't have correct fuel delivery....it's now 64 days until the track opens...do you know where your fuel pressure is?
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Old 01-04-2003, 04:06 PM
JoeGrapes JoeGrapes is offline
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Well, I'll tell you what. My 440 Cuda was originally a 383 car. It had 5/16 fuel line. When I put in a modified 440, about 450 HP, I didn't change the fuel line or the stock fuel pump. The car ran 13.2@106 and and crossed the line at about 6200rpm with no hint of starving for gas. So all the stuff you heard about 5/16 fuel line being to small for anything over a 318 is bull on a street car. I'm redoing the underside of the car now, so I'm going with 3/8 line as long as I have everything apart. Also, you have to change the tank pick up as it is 5/16 to.
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  #8  
Old 01-04-2003, 04:38 PM
George G. Leverette George G. Leverette is offline
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What did the 426 Hemi's and 6 Pak 40s run for fuel line size? What size fuel lines are they running on the king of the street cars. What is the formula for calculating the amount of fuel flowing through different size orfices?
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Old 01-04-2003, 06:17 PM
JoeGrapes JoeGrapes is offline
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The 5/16 lines were used on motors up to and including the 383. All the 440's and Hemi's used 3/8 lines.
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  #10  
Old 01-04-2003, 07:24 PM
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most (if not all) 383-4bbls also had the 3/8 line.

A 3/8 line is about the max that you want to put before a mech. fuel pump. other wise, the fuel begins to get too heavy for it to pull. You can go larger than 3/8 if you are running an electric fuel pump at the tank.

As far as the sender goes, you cn replumb your existing sender for the 3/8 line and it will cost about $100 less than the correct 3/8 sender.
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  #11  
Old 01-04-2003, 07:29 PM
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Dan
If you do not plan on building much h.p. over 400 then 3/8 is ok.
It appears you are still running the stock style fuel pump. This is my opinion & I know there are many that will disagree, but I like electric pumps that do not require unneeded friction on internal parts of my engine. The added plus to this is less or no vapor lock & steady fuel pressure.
This is why my 340's will have the same fuel line as my 500 ci wedge. It all is depending upon you budget, if you can stand the upgrade to larger line do it. You will, if like most racers, move your h.p. level up when you can afford it. If you already have a fuel system in place to handle it, then this will not be factor on any adjustments @ that time.
Been there & done it. finally get the money & the parts & all completed. Ready to race to find out @ w.o.t. there is not enough fuel. All i"m trying to say is make smart changes. A little more money now will save you a lot down the road, if you are a serious
racer.

Bash me now boy's I'm over - ha, ha , ha
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  #12  
Old 01-05-2003, 01:07 AM
gerard gerard is offline
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Default fuel line

your wrong.up to 69 all 383, and 440's had 5/16. the 69 1/2 6-bbl cars also have 5/16 lines. hemi had 3/8
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  #13  
Old 01-05-2003, 04:21 AM
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Bonk - wrong answer.

When I bought a new fuel sender for my '68 Charger, they listed both the 5/16 and the 3/8. The old parts catalog showed the 383-4 & up used the 3/8 sender and that anything below used the 5/16 sender.
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  #14  
Old 01-05-2003, 11:56 AM
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Quote
"5/16 fuel line being to small for anything over a 318 is bull on a street car. I'm redoing the underside of the car now, so I'm going with 3/8 line as long as I have everything apart.?"

..and you'll see the results in your time slip.

Street car? of course it'll work but if you take it to the track the bigger lines will almost always improve your ET and MPH.

If this is all wrong than I guess all the science of BSFC is bunk and we need to re-write the book on line size flow capacity.

This is not Hocus Pocus it's science, based on how much fuel an engine needs to produce "X" HP at a given RPM and what size pump and fuel lines are required to deliver that fuel.

Of course if your running a 500 HP engine bolted to a stock convertor and a 2.73 gear with a vacuum secondary 600 Eddy carb in a 4000# car of course you won't need as much fuel as the engine never reaches it's max RPM within a measured time frame that would require much more fuel than a stock motor...but add a 5000 stall convertor, 4.88 gears, a 750 Mighty Demon. cut it down to 3000#s..... drive it like you stole it and I'll guarantee you that the 5/16 lines won't keep up.

Have a look here to get a better understanding of BSFC:
http://www.westechperformance.com/pa...ding/bsfc.html

Once you understand the science you'll be able to size your pump and lines correctly for your motor.

Steel boats will never float, the world is flat, computers are just a fad, and when they finally get those square screen color TV's perfected I'll buy one.
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  #15  
Old 01-05-2003, 01:18 PM
cyril69 cyril69 is offline
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Quote:
Originally posted by ehostler
most (if not all) 383-4bbls also had the 3/8 line.

A 3/8 line is about the max that you want to put before a mech. fuel pump. other wise, the fuel begins to get too heavy for it to pull. You can go larger than 3/8 if you are running an electric fuel pump at the tank.

As far as the sender goes, you cn replumb your existing sender for the 3/8 line and it will cost about $100 less than the correct 3/8 sender.
Do you have any information on how to replumb the sending unit from a 5/16 line to 3/8 line as I need to do this. I like the idea of saving the $100.

Thanks Cyril
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  #16  
Old 01-05-2003, 01:52 PM
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Part number CE 8077
Here's the link
http://www.chassisengineering.com/start/
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  #17  
Old 01-05-2003, 04:34 PM
451Mopar 451Mopar is offline
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My friends Charger has ran low 12's with 5/16" line, but that is with an electric fuel pump. I think his engine was possably making around 450-500 HP?
3/8" line would be better and I think this is about the largest you would want using the mechanical fuel pump because under acceleration the "G" force will try to push the fuel back to the gas tank, and the mechanical pump has a harder time pulling the fuel (under high "G" acceleration.)

For 400 Hp, I think the Carter High Volume pump should work fine.
I prefer the higher pressure "strip" pump with a regulator.

Electric pumps work good for fuel delivery, but I din't know of a quiet performance one, maybe an OEM may work? All the performance pumps I have seen or used were pretty loud.
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  #18  
Old 01-05-2003, 04:42 PM
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Quote:
Originally posted by cyril69


Do you have any information on how to replumb the sending unit from a 5/16 line to 3/8 line as I need to do this. I like the idea of saving the $100.

Thanks Cyril
Someone posted about this in the vintage or restoring forums.

The basics are:
[list=1][*]Remove exisiting sender[*]bend 3/8 line to match the exact bends of the 5/16 line that's on the sender[*]carfully remove the float assembly from the existing setup[*]remove the 5/16 line[*]open the whole to fit the 3/8 line that you bent to shape, earlier[*]now using a propane torch, solder the 3/8 line into the sender plate[*]with a heat sink on the float assembly, solder it onto the 3/8 line[*]install the proper sock[*]reinstall the 3/8 assembley into the tank[/list=1]
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  #19  
Old 01-05-2003, 05:02 PM
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451...too loud??? you obviously spent way too much money on mufflers...I can't even hear mine run...

Loud Pipes Save Lives!
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  #20  
Old 01-05-2003, 10:40 PM
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Default bsfc????

Hey cuda66273, do you even know what bsfc stands for??? It has nothing to do with in car dynamics. Geeze, Don't give out wrong info to sound cool.

The harder the car launches, the harder it is for a mechanical fuel pump to pull fuel from the tank. Why do roundy pounder guys make 700 hp on mechanical pumps???? Nothing to do with brake specific fuel consumption at all. A 5/16 line will feed 500 hp if it has an electric pump mounted and wired properly. I've had 11 second cars with 5/16 lines.

Never exceed the speed of your IQ.
Telling it like it is.
M.S.

PS. How 'bout somebody posting a sticky about bsfc? We could all learn something. How about it cuda66273?
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  #21  
Old 01-05-2003, 11:01 PM
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Hey Madscientist, if you went 11's with 5/16 fuel line, it must have been a 2200 lb. or lighter car. I had nothing but grief with 3/8 line even with an electric pump. The car would never run the same way twice. One day at the track a guy running a Cleveland in a '68 Cougar says switch to 1/2" fuel line and solve all your problems. He then goes on to tell me that his car picked up 1/2 a tenth with no other change than going to 1/2 " line. It was a low 11 second car. I switched to 1/2" and I promise I'll never run anything smaller on a performance car unless it's a tilt 6 or smaller. That was over ten years ago-no fuel problems since............djs
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  #22  
Old 01-06-2003, 07:15 AM
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Default Re: bsfc????

Quote:
Originally posted by madscientist
Hey cuda66273, do you even know what bsfc stands for??? It has nothing to do with in car dynamics. Geeze, Don't give out wrong info to sound cool.
The harder the car launches, the harder it is for a mechanical fuel pump to pull fuel from the tank. Why do roundy pounder guys make 700 hp on mechanical pumps???? Nothing to do with brake specific fuel consumption at all. A 5/16 line will feed 500 hp if it has an electric pump mounted and wired properly. I've had 11 second cars with 5/16 lines.
Never exceed the speed of your IQ.
Telling it like it is.
M.S. PS. How 'bout somebody posting a sticky about bsfc? We could all learn something. How about it cuda66273?
Man, do you have some kind of grudge or what? This should help others on the BSFC issue.

http://www.westechperformance.com/pa...ding/bsfc.html

I would just like to agree with you on the fact that Winston Cup engines are fed with mechanical pumps, but they have positively nothing in common with a diaphragm type pump which most people associate with "mechanical" pumps. They are belt driven and very high volume. I would also like to point out that it is possible to feed a low geared, high output race-only vehicle with 5/16 line, but the PRESSURE has to be upped to deliver the same amount (volume or weight) of fuel which is required to feed the engine it's needed pound # per hour of fuel (what ever it may be) through the smaller line. (isn't that something like BSFC?) The law of pressure states that if flow (pounds per hour of fuel) stays constant, and resistance to flow is increased, pressure will rise. That is in fact, is all that pressure is--a measure of resistance to flow. I guess if you use a fuel with an ultra-high specific gravity you could get by with less volume (and therefore less pressure), but I am no authority on BSFC. The bottom line being--if you have an engine that consumes .5 gallons per horsepower per hour, and your fuel pressure must remain below 8 p.s.i. on the carb side of the regulator, you must have the larger line to deliver the fuel at the lower pressure. If you put the same amount of fuel through a smaller line, the pressure will rise to un-usable levels.

On another note, I would assume from other responses to your posts that it is the general consensus of this online community that you should use your knowledge to more constructive and less critical posting. The belittling of others is in no way of benefit to anyone except perhaps to your self-image, and I would like to point out that there is no knowledge to be gained from your previous post. I am in no way trying to pick a fight or be mean, I simply would like to maintain the friendly (and very helpful) atmosphere that I have enjoyed since I joined moparchat, and I urge you to do the same.
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Old 01-06-2003, 03:01 PM
451Mopar 451Mopar is offline
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OK my car is still pretty loud, even after installing the TTI 3" exhaust system with the Dynomax mufflers. I can hear my Mallory 250 GPH fuel pump pretty good, and it is quieter than some of the Holley electric pumps or Aeromotive pumps.
I can't coment on the BG pumps bacause I don't know anyone with one.
The car is plumbed with #8-AN (about 1/2" fuel line) and runs a bypass type regulator. The setup is overkill on the street (with my 455 RWHP), but it never vapor locks
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Old 01-06-2003, 04:35 PM
George G. Leverette George G. Leverette is offline
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Still a lotta mis-information on this subject, "How much fuel will flow through an orfice of a given size at a constant pressure is the question" anyone got the answer???????
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Old 01-06-2003, 05:08 PM
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i wanna thank domeone else for opening this can of worms. i have a lot of the same questions, but felt kinda stupid, so i didnt ask.
if im readinfg all this right, a 3/8 line, mechanical pump setup will be fine for a car making 450 horse, naturally aspirated, if it weighs around 3300 pounds and is geard fairly stiff. (i hope im right, cause this is what im shooting for). tell me if im wrong.
as for fuel line material, what would yall recommend for a car that is primarily street, but sees occasional track time, both at road-events, and the strip? i was thinking aluminum, but i got the impression that that may be a bad idea.

so please, while continuing the ongoing discussion, (dont wanna be a topic changer) explain this to someone who is fuel delivery system stupid.
thanks yall
mike
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Old 01-06-2003, 06:07 PM
Billydelrio Billydelrio is offline
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My experience with fuel delivery: I was racing my 66 Mustang back in the mid 80s & early 90s. It would 1/4 at 14.50 around 90 mph making around 180 rear wheel hp with a 302. The factory type mechanical pump and stock 5/16 (I think) line would put out about 4.5 to 5 psi during normal driving conditions, but would drop to below 1 psi at the top end of a 1/4 mile run. My Dart has two electric pumps and two 1/2" lines in parrallel and the pressure is 7 psi ALL THE TIME (when the pumps are on of course)
Duncan had a Carter mechanical pump feeding his 426 Hemi and it would fall on its face at the top of 3rd if he ran it wide open. If he ran hard, but not all 8 bbls wide open, he could get it passed 3rd and then hold it wide open in 4th. I don't recall it falling on its face in 4th gear because by that time I was ready for him to let off the gas anyhow.

If you really want to know what your fuel system is doing, then a fuel pressure gauge is a must.

Billy
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Old 01-06-2003, 08:18 PM
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Quote:
Originally posted by George G. Leverette
Still a lotta mis-information on this subject, "How much fuel will flow through an orfice of a given size at a constant pressure is the question" anyone got the answer???????
That is a hard question to answer because pressure is the variable in that scenario. Pressure has a direct relationship with flow, and an indirect relation with restriction. As the flow increases, pressure will rise. As the line gets smaller, pressure increases. I will have to dig out the old books and re-research some more and maybe I can shed a little light.
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Old 01-06-2003, 10:54 PM
cyril69 cyril69 is offline
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Thanks Ed for the info.

And to the others talking about pressures and flow just remember a squirt is just a drip under pressure.

Thanks Cyril
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  #29  
Old 01-08-2003, 11:07 AM
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11 second car requires a fuel flow of 1 gallon 6#'s of fuel flow in 30 seconds.....6#x2= 12#'s per minute x 60min.=720#s per hour/6#'s per gal=120 GPH so now figure the fuel pressure required to push that amount of fuel through a 5/16 line.

Sure it's possible....how long will the pump last? How many amps will it be pulling? How hot will the pump get?

The simple solution is a pump capable of pushing that quantity of fuel without any restrictions in line such as inadaquate filters, dented and dinged hard lines, rust and corrosion in stock lines, poorly designed fuel fittings (90* cast, Cheap imitation AN fittings) limited flow Pressure Regulators($23.00 units), restrictive tank socks, front pick-up stock tanks and G force effect on the fuel in the system on a launch....MS ....you know all these factors effect fuel flow and you also know the best way for the AVERAGE guy to avoid these problems in fuel delivery is with larger fuel lines, a pump that can keep up with the engine requirements and last for years with continuous street duty.

I stand by my recommendation.....over 400 HP you should switch to a 3/8 or -06 line and a good pump and a unrestricted delivery system to handle the fuel delivery correctly...filter, regulator and fittings.

If you have a better calculation I'd like to see it.

Dusterbd:
The 3/8 hard line will be fine, but be sure the whole system is restriction free ...12 sec car-1 gallon in 35 seconds, 11 sec car-30 seconds...etc.

If you follow this rule of thumb you shouldn't have any problems with fuel delivery.
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Old 01-08-2003, 12:34 PM
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As someone said you can get into a big can of worms trying to explai pressure, volume and line sizing. The main thing to remember is the your fuel system flows to the smallest size component. It does not help to run -8 line if you have a -6 fitting at the tank. It also depends on the type of pump, regulator, and other components. The most basic rule of thumb is the more HP the bigger the fuel line. A lot of people get confused watching racing not realizing that yes they use a certain size hose but a using a very special highpressure high volume fuel pump designed to push a lot of fuel thru the smaller line mandated by their sanctioning body. A lot of these pumps would never work on the street, due to the fact that it would burn them up.


http://www.russellperformance.com/te...lwhat_hose.htm

Also consider whether or not your carb(or fuel injection) can handle the excess fuel from the larger lines, too much fuel can cause a vehicle to fall flat on its face as well.
My 2 cents, this time, putting on flack vest for replies.
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