fuel line issues-anyone else?

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Aug 14, 2009 | 08:41 PM

straub18045

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Racer

Joined: Jun 2006

Posts: 476

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From: Easton PA

fuel line issues-anyone else?

so i just got back from another dissapointing time at the track. my issue is im runing out of fuel at the top end. only happens when i slap the drag radials on, must be because of the g force. my engine builder say i need 1/2'' lines now. i just put on the holley 170 gpm fuel pump with a regulator set at 7.5 psi, so its not the pump. but it got better by going to larger pump. wanted to no if any of you guys had same issue and how did you run the lines.

my combo-
late model block
eagle crank
pm connecting rods
kb forged pistons
edlecbrock rpm cam
edelbrock large valve e-tec heads
rhoades lifters
airgap intake
built q-jet
gm hei
11.13 compression
not dyned but est. 475 horse
700r4 conversion
stoxk rear

Aug 14, 2009 | 11:12 PM

dstaley

Pro

Joined: Jul 2005

Posts: 517

Likes: 7

From: Peoria IL

What fuel lines are you using? Any AN fittings?

Aug 15, 2009 | 09:32 AM

Ironcross

Race Director

Joined: Nov 2002

Posts: 12,142

Likes: 54

From: Taylor Michigan

3/8 lines are more than adequate, no need for 1/2 inch. Get yourself a good tuner that can use what you have to its potential...

Aug 15, 2009 | 09:57 AM

marz

Burning Brakes

Joined: May 2006

Posts: 774

Likes: 1

From: Round Rock Texas

I had the problem with the 76 I built of stalling when I turned and off any hard launches. I had to install a fuel sump in the gas thank to be sure there was always adequate fuel. You might ask your local Vette pro about it.

Aug 15, 2009 | 01:27 PM

straub18045

Thread Starter

Racer

Joined: Jun 2006

Posts: 476

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From: Easton PA

im using stock fuel lines, an fittings at regulator and pump, replaced fuel sock, and rubber lines. the car is dialed in with wideband o2, fuel and spark curve are dead on. only happens with drag radials. fuel sump mite be something to look into but didnt think this combo would be that healthy were i would need bigger lines or a sump. o ya and reset float at max setting.

Aug 15, 2009 | 01:36 PM

dstaley

Pro

Joined: Jul 2005

Posts: 517

Likes: 7

From: Peoria IL

It is possible.the AN fittings are a part of the problem. -6 AN fittings almost always have less than a 1/4" bore, and that's for straight fittings- if they have any curve to them at all, you will find that they're even more restrictive.
In order to maintain at least 0.375" minimum I'd in the fittings, you will have to use at least -10 AN fittings. This varies a little bit from brand to brand and P/N to P/N, but not much.

This problem does not exist with inverted flare fittings, so if you dtick with them you don't have to buy grossly oversized parts to get the minimum I'd you're looking for.

Aug 15, 2009 | 01:44 PM

straub18045

Thread Starter

Racer

Joined: Jun 2006

Posts: 476

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From: Easton PA

i do have a couple 90 degree an fittings, we had to step down the lines so much going in and out of pump because of the big inlet and outlet ports on the pump, it boast 170 gpm but not though my 3/8 lines im sure.

Aug 15, 2009 | 01:49 PM

dstaley

Pro

Joined: Jul 2005

Posts: 517

Likes: 7

From: Peoria IL

I would bet a brewski that if you pull one of those 90 degree fittings loose you will find that the bore through them is on the order of 3/16 - 7/32. That can't help at all, especially on the suction side. Take care of that and let us know how it works out, OK?