Dual Feed Fuelline leak - Team Camaro Tech
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post #1 of 19 (permalink) Old Aug 20th, 03, 12:16 PM Thread Starter
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Does anyone know if there is supposed to be some type of gasket as part of the inverted flare fitting on a holley carb? I have a holley 750 HP carb and a holley chrome fuel line. I cannot seem to get the fitting to seal up. It leaks between the fuel line and the nut that screws the fuel line to the carb fuel fitting. I'm on my second fuel line and have cleaned everything up with brake cleaner with no luck. Am i missing a washer or gasket or does an inverted flare seal metal to metal?

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post #2 of 19 (permalink) Old Aug 20th, 03, 03:47 PM
 
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I go thru this each time I change carbs. Once I have them so they don't leak,I leave the chrome fuel lines on when I remove the carb. You may want to try putting teflon tape on the threads and gradually tighten the nuts till there is no leak.
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post #3 of 19 (permalink) Old Aug 20th, 03, 07:55 PM
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Greg inverted flare fittings are metal to metal seals. If it leaks there is a problem with the flare or it's mating surface. Something as simple as a scratch on the sealing surfaces will cause a leak. It's also possible the aftermarket line you are using may not be true or the exact center to center dimension causing the sealing surfaces to be slightly misaligned. Seco makes a soft metal conical seal that can be installed between the flared line and the fitting just for this purpose. I've only used them on standard AN fittings, never tried one on an inverted flare. They come in aluminum and nickel. I know only the nickel are approved for aerospace applications and then it's up to each manufacturer, but I've had good luck with them on scratched fittings, or ones that simply won't seal.

I make my own Holley dual inlet double flared lines and use an inverted flare brass tee fitting. I've never had one leak.
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post #4 of 19 (permalink) Old Aug 22nd, 03, 12:45 PM
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There is a gasket that goes between the fuel inlet nut and the fuel bowl. Sometimes they can leak there and mimic a leak at the fuel line to inlet nut fitting.

But my guess is that your carb is leaking exactly where you say it is. Sometimes those can be a real bas---- to seal. If this is your second fuel line, chances are that you have a burr or a scratch on the fuel inlet nut. I'd examine those closely and replace if needed. Teflon tape won't help, as these fittings do not seal at the threads. The threads just provide the mechanical force to effect a metal to metal seal.

Good luck!


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post #5 of 19 (permalink) Old Aug 22nd, 03, 01:37 PM
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Here's something I've found with any type of solid lines, be it copper oil pressure or steel fuel lines like your chrome ones or factory "Y" block lines. This goes for solid brake lines as well. Any time you have the slightest bend on the end of the line you will have a leak. The part that is hidden under the tightening nut has to be as straight as possible, no dents, dimples or bends, even the slightest bend will cause a leak. I've seen poor condition flairs not leak and good flairs that have a ever so slight bend just below the flair leak...

The pic's show just how little it takes to have a leak... The end on the left in both pic's doesn't leak and the one on the right does no matter how tight or what it's connected to. In this case I tried 2 different carbs and 2 different "Y" blocks and the leak followed the fuel line...





[ 08-22-2003, 04:56 PM: Message edited by: DjD ]

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post #6 of 19 (permalink) Old Aug 22nd, 03, 04:26 PM
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my tranny cooler line on top of the radiator was leaking since I bought the car. My mechanice cut the line, redid the double flare and it still leaked. He then cleaned the surface with spray cleaner and inside the radiator threads, then greased all the threads with brush on axle grease and then tightened again. That extra ability to slip into place when tightening with a line wrench did it and it has not leaked since. Its a trick worth trying but I agree with the others, any knick or bend is asking for a leak.
good luck, let us know how it goes.
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post #7 of 19 (permalink) Old Aug 28th, 03, 03:06 AM Thread Starter
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I give up on the chrome line. I've tried two different holley lines. I cleaned them both really well. The look straight with no nicks. My fuel inlet fittings looks fine too. But they still leak like a seive. I've installed them bare, with teflon tape, etc with no luck. I just ordered a Russel dual feed line from summit. I hope this solves my problem. Only problem was that it totaled to about $80 with all the fittings and adapters.

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post #8 of 19 (permalink) Old Aug 28th, 03, 04:49 AM
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The "Chrome Sucks" monster strikes again. Sorry about your leaks there, but I wish the manufacturers would read all the posts about their chrome crap and leaks.
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post #9 of 19 (permalink) Old Aug 28th, 03, 08:33 AM
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The "chrome" dual feed lines are usually just chrome(or something) plated copper. I'm guessing that if you could remove the plating from the flared end, the softer copper would conform easier to any irregularities and seal.

In fact, I bought a Z/28 repro fule line kit for my FB385 (fits perfectly with a Holley 650 DP, FYI). The lines that run to the carb from the Y-Block were made of steel, and it was so hard that I had to crank them down as hard as I could to get them to seal. When I'd remove them, it would round off the nut, which made them worthless. I made my own replacements out of 5/16" copper tubing, and they work great - just a reasonable amount of force and they seal.

[ 08-28-2003, 11:51 AM: Message edited by: BPOS ]


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post #10 of 19 (permalink) Old Aug 28th, 03, 01:48 PM
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Copper tubing isn't a great idea for that application - copper tubing that's subjected to vibration work-hardens and eventually fractures; that's why the OEM fuel lines between the pump and carb were steel. Same reason older Corvette oil pressure gauge pipes were copper-plated steel (they LOOKED like copper tubing, but they weren't - they were steel). [img]graemlins/thumbsup.gif[/img]

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post #11 of 19 (permalink) Old Aug 28th, 03, 02:40 PM
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Yeah, I know and thanks for the tip..if I could find a some steel tubing that was a bit softer I'd use it...but the stuff I that came with the kit was worthless.


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post #12 of 19 (permalink) Old Sep 1st, 03, 11:04 AM
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GregD: I had the same problem with 2 chrome fuel lines and several adapter nuts to the carb. I finally went with a Holley regulator and braided lines. It looks better and works mint, but it did set me back about $120.00.

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post #13 of 19 (permalink) Old Sep 1st, 03, 03:52 PM
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Ditto on the leak. I ended up replacing the fittings that go to the carb with brass ones from holley. That fixed my leak.

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post #14 of 19 (permalink) Old Sep 2nd, 03, 12:51 AM
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BPOS, take your fitting to a hydraulic & pnuematic hose/tubing vendor and get the copper sealing washers which fit the flare. This will solve your problem.

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post #15 of 19 (permalink) Old Sep 2nd, 03, 06:04 PM
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Thanks for the tip, Everett. I already rounded the nuts off of the steel lines. I should have another set made and get the copper washers. I assume they go between the flare end of the tube and the inlet nut. Will they "work harden" and fracture as JohnZ stated in his post? If I could find a decent flaring tool I'd make my own. Those hardware store tools can't grip the tubing tight enough after a few flares and are essentially junk.


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