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Author Topic:   Fuel Line sizing
65_289
Gearhead

Posts: 761
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Registered: Jul 2001

posted 04-16-2003 05:38 PM     Click Here to See the Profile for 65_289   Click Here to Email 65_289     Edit/Delete Message   Reply w/Quote
Would there be any benefit of running a 1/2" fuel line if the inlet & outlet of the pump is 3/8"? Or would the extra capacity go to waste? I'm trying to decide what size line to run when I install the Mallory 140 & hook up the nitrous. Thanks!

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Fastymz
Moderator

Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 04-16-2003 07:07 PM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
Are you going to run a line just for the nitrous?
I'd think that the 3/8's line would be big enough.

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SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

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65_289
Gearhead

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Registered: Jul 2001

posted 04-16-2003 07:25 PM     Click Here to See the Profile for 65_289   Click Here to Email 65_289     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Fastymz:
Are you going to run a line just for the nitrous?
I'd think that the 3/8's line would be big enough.


No, I'm running 1 pump for both. I'll put a "Y" in the engine bay & split to 2 regulators.

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jkilroy
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Posts: 1797
From: Vicksburg, MS
Registered: Dec 99

posted 04-16-2003 11:58 PM     Click Here to See the Profile for jkilroy   Click Here to Email jkilroy     Edit/Delete Message   Reply w/Quote
The price difference is minimal, run the larger line. Having too much fuel with N2O is not bad, *too* little is very bad.

------------------
Jay Kilroy
68' Fastback GT 390
"No such thing as a cam thats too big"

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65_289
Gearhead

Posts: 761
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Registered: Jul 2001

posted 04-17-2003 12:22 AM     Click Here to See the Profile for 65_289   Click Here to Email 65_289     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by jkilroy:
The price difference is minimal, run the larger line. Having too much fuel with N2O is not bad, *too* little is very bad.


Good point!

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MrWesson22
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Posts: 1212
From: Dacula, GA
Registered: Sep 2000

posted 04-17-2003 05:51 PM     Click Here to See the Profile for MrWesson22   Click Here to Email MrWesson22     Edit/Delete Message   Reply w/Quote
Is there really a bad side to running line larger than you need, either for motor or n2o?

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Neal

69 Gulfstream Aqua Grande
351C/4sp
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Toronado3800
Gearhead

Posts: 364
From: St. Louis, MO
Registered: Jul 2001

posted 04-17-2003 06:14 PM     Click Here to See the Profile for Toronado3800     Edit/Delete Message   Reply w/Quote
I dunno for sure. But I could imagine a garden hose sized line might lower pressure...but would that hurt the amout of fuel available to your carb or injectors?

While I'm wondering, does anyone buy fuel pumps for late model fuel injected cars for use on their hot rods? My Olds has 35lb an hour injectors and the guage on my 351W in my stang says that Carter pump only puts out 7lbs.

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Fastymz
Moderator

Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 04-17-2003 06:40 PM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote

I would think A line thats to big.Would lower the flow rate as the RPM's go up.You'd need a much larger pump,or many pumps to keep the same flow rate as a smaller line.

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SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

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65_289
Gearhead

Posts: 761
From:
Registered: Jul 2001

posted 04-17-2003 08:36 PM     Click Here to See the Profile for 65_289   Click Here to Email 65_289     Edit/Delete Message   Reply w/Quote
This is interesting. I had never thought about losing pressure. I guess they make the inlets & outlets a particular size for a reason. I wonder if fuel pump flow rates are rated for a specific fuel line diameter. Anyone know?

[edit] Mallory recommends a 3/8" or bigger line for the Comp 140, and it has 3/8" ports. So I guess that answers that.

Thanks for all the replies!

[This message has been edited by 65_289 (edited 04-17-2003).]

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Moneymaker
Administrator

Posts: 21725
From: Lyons, IL, USA
Registered: May 99

posted 04-17-2003 08:40 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Toronado3800:
I dunno for sure. But I could imagine a garden hose sized line might lower pressure...but would that hurt the amout of fuel available to your carb or injectors?

While I'm wondering, does anyone buy fuel pumps for late model fuel injected cars for use on their hot rods? My Olds has 35lb an hour injectors and the guage on my 351W in my stang says that Carter pump only puts out 7lbs.


Not with that bigass Mallory fuel pump it won't.

------------------
Alex Denysenko
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65_289
Gearhead

Posts: 761
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Registered: Jul 2001

posted 04-17-2003 08:42 PM     Click Here to See the Profile for 65_289   Click Here to Email 65_289     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Moneymaker:
Not with that bigass Mallory fuel pump it won't.

LOL.

If the Comp 140 is big-ass, what does that make the Comp 250?

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bluestreek
Gearhead

Posts: 1460
From: Athens,GA
Registered: Jul 2001

posted 04-17-2003 09:04 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by 65_289:
LOL.

If the Comp 140 is big-ass, what does that make the Comp 250?


I don't know, but if you hook a water hose to it you would have your own car wash!

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1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, TFS alum. heads, ported Stealth 8020 intake, Xtreme 274 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
2nd pass: 12.11 @ 114 mph
DanH

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N266fords
Gearhead

Posts: 1039
From: Spokane ,WA USA
Registered: Apr 2003

posted 04-18-2003 05:31 PM     Click Here to See the Profile for N266fords   Click Here to Email N266fords     Edit/Delete Message   Reply w/Quote
run the 1/2 line but you may want to run a seperate fuel pump for your nos as to low of pressure from the fuel pump when the nos is flowing will lean your motor out not a good thing I say this if you are running over 100 hp shot also you will need to retard timing and run ressed (shorter) plugs and hotter ign lik msd if you are going 200hp or more of nos

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65_289
Gearhead

Posts: 761
From:
Registered: Jul 2001

posted 04-18-2003 06:03 PM     Click Here to See the Profile for 65_289   Click Here to Email 65_289     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by N266fords:
run the 1/2 line but you may want to run a seperate fuel pump for your nos as to low of pressure from the fuel pump when the nos is flowing will lean your motor out not a good thing I say this if you are running over 100 hp shot also you will need to retard timing and run ressed (shorter) plugs and hotter ign lik msd if you are going 200hp or more of nos

Thanks for the suggestion. I have a Hobbes switch that will turn of the nitrous if the fuel pressure drops too low.

And it's an NX kit, not NOS.

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