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Fuel leak at KBL carburetor junction

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jim.eakin
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Fuel leak at KBL carburetor junction

Post by jim.eakin » Tue Jun 25, 2019 3:33 pm

When I first fired up my KBL engine (first time from rebuild), I spotted a fuel leak at the 3-way junction for the fuel lines for the triple carbs. So I dismantled everything, made sure the pipe threads were sealed, and put it back together at tight as I could get it. Still leaked.

Turns out the flare fittings were just too bunged up to hold pressure anymore. Since it was a flared fitting, the only way to replace it was to cut it off the copper pipe (yes, destroyed the originality, but hey, can't allow leaks). Down at Lowes and Home Depot, no luck finding a replacement.

I call Jim Staib at Fine Wood Boats last Sunday. He said he was out on his porch enjoying his day. When I explained my problem, he told me that the "uni-flare" fittings were long ago discontinued (unobtanium) and I would have to start over.

I did some research on the web. I learned that copper lines were great back in the day, but were prone to work hardening and leaking. It's recommended to use rubber fuel lines these days. So I ordered the fittings I needed to go from 1/8 NPT to 1/4 ID fuel lines. Complete loss of originality, complete safety.

Still not satisfied, I looked at how to preserve using copper. I learned that compression fittings should not be used for fuel lines - only flared lines should be used. I might still put together some connections using copper to put on later.

I'd be interested in hearing what others are doing with their fuel lines in these classic boats. Also, would replacement with modern flared fittings, where required (to fix leaks), affect how this part of the boat is judged? Is this even noticed by judges?
1952 CC Riviera 18, KBL

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Bilge Rat
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Re: Fuel leak at KBL carburetor junction

Post by Bilge Rat » Tue Jun 25, 2019 9:13 pm

To me a "safety first" attitude trumps (sorry, bad choice of word) judging on originality. I too had a similar issue when re-plumbing a dual carb MCL but my situation was that most of the uni-flare fittings were missing anyway.

I chose brass fittings from McMaster Carr's line of Yor-Lock double compression fittings and used 5/16" copper pipe. The Yor-Lock fittings are available in brass or stainless steel but their bendable stainless tubing was only available in full coils so I used thicker copper. I only needed about 4 feet. The Yor-Lock fittings are a DOT rated heavy duty fitting rated for high temperature and high vibration, not anything like the Home Depot grades. They are compatible with Swagelock, another standard heavy duty fitting and are approved for gasoline. They have 2 compression rings in the fitting. Here's a link to a male 90 degree fitting on their website: https://www.mcmaster.com/5272k307

Here's some pictures of how the fittings and pipe look on the engine.
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1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

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jim.eakin
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Location: South Orange County, CA
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Re: Fuel leak at KBL carburetor junction

Post by jim.eakin » Wed Jun 26, 2019 12:28 pm

Great, this really helps. Thank you.

For others that might be reading this: the fittings in the KBL Zenith carbs (90 degree) and in the triple junction are 1/8 NPT. I did some research on fuel flow and it does seem that 1/8" copper pipe would flow enough fuel for the short distance from the junction to the carbs, although the original pipe is 1/4".

(Great to see that the Yor-Lok fittings do not require that the pipe be flared with a flare tool.)
Yor-Lok fitting.png
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1952 CC Riviera 18, KBL

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Bilge Rat
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Re: Fuel leak at KBL carburetor junction

Post by Bilge Rat » Wed Jun 26, 2019 4:09 pm

You're welcome. Just be sure that you verify the pipe lengths and bends are correct before final tightening of the fitting nuts. Once fully compressed, the 2 rings will never come off again!

Ask me how I know. Fortunately they sell compression sleeves and nuts separately.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

jim g
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Re: Fuel leak at KBL carburetor junction

Post by jim g » Wed Jul 03, 2019 7:48 am

Mcmaster Carr has DOT compression fittings (not yor-lok fittings) and the nuts look just like the original compression nuts.

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