Board index Flathead Power-Technical Questions, Answers, and Suggestions Knuckles Sealing inyake nipples

Sealing inyake nipples

Moderators: Curt!, Pa

Post Mon May 05, 2014 12:30 pm

Posts: 530
Location: Ogden, Utah, USA
Was reading an online carburetor repair bolg. The owner has a good reputation and has to work with some old stuff. This is the webpage:
What he has found to work with Cork floats is,
The old shellac material will not work with modern fuels. So he now coats them with Por-15 and lets them dry for 72 hours. Might this also work to seal the intake nipple and help prevent air leaks? If modern fuel won't eat this stuff off a float it might be good for us as well. Any thoughts? It would work on flatheads as well if it don't get too hot? What do you guys think?
Steve H

Post Mon May 05, 2014 4:12 pm

Posts: 128
Location: BRANFORD, CT

Hi Steve,

Coating floats makes them too heavy (like the brass) so they do not react like the cork does and gives lousy performance.
Don't use it on the intake seals either.
Check out my Rubber Duckeys and PEEK intake seals.
Technology has come a long way in the 75+ years since the original float and seals were designed.
I like to ask guys (if they are old enough) if the remember the brass trap under the sink which used similar plumbers seals. Then I ask if they remember the pan that was kept under it to catch the drip.
When they started using plastic seals in the late 1950's the pan was not needed anymore!
Bruce Argetsinger
AHRMA Dirt Track # 67J

Post Thu May 08, 2014 5:10 am

Posts: 1643
Location: Interlaken, NY USA

Bruce, I remember that pot under the sink! Great analogy. I'm installing a set of your Peek seals on a buddie's Knuck as we speak. Great stuff.

Post Thu May 08, 2014 9:52 am

Posts: 530
Location: Ogden, Utah, USA
The peek seal I know about. Cotton was the one I learned that from. I was thinking about sealing the intake nipple in to the head. We have talked about everything from white lead to Locktite with unpredictable results. The rivet holds the nipple in place and on the Knuckle there is a very thin face to seal against the nipple. I was thinking this might be a suitable sealing product that might not be too permanent. Of course the nipple on a flathead must seal to the cylinder thus the thought about heat. Coating the threaded area might help prevent air leaks and help hold the nipple tight with the rivet providing the mechanical lock. I don't know what the best way to break this material down would be, but if it will hold up with modern fuel it might worth thinking about.
Steve H

Post Sat May 10, 2014 6:54 am

Posts: 3011
Location: Central Illinois, USA

I wasted a couple of thousand dollars worth of NOS cork Linkert and Schebler floats by coating them with POR15.
It turned out that they wouldn't last overnight in my local P4gas!

I then pioneered the re-introduction of "nitrophyl" floats by machining them from a material similar to the original "Armstrong" floats of the '50s and '60s.
It took a few years before they became subject to swelling.
By June of '08, however, an improved formula became available, and I am able to replace any "bloats" free of charge with a material that has proven itself, so far...
Its all about the fuel, of course, and you never know what's going to come out of the next pump.

Please note that this material is still under patent with a severe royalty for molding, so it is only available in machined form.

And when I pioneered the use of PEEK for manifolds,, several thing became apparent about insuring its success.

First, bubble-testing is manditory for certainty of a perfect seal:

The next was that the seal must be a tight, "stretch-on" fit, with no blemishes upon the manifold spigots, If worn the ends of the spigots were larger than the sealing area. If scarred or nicked, the blemishes impressed into the PEEK, greatly reducing their chances of sealing, and greatly reducing the re-useability of the expensive seals in the future.
Slip fits required excessive torque upon the nuts, the very thing that PEEK was intended to avoid.

Even brand new manifolds from different sources varied too greatly for me to cut them "blind".

Then, on this forum, the problem of repeated loosening of the nuts was brought to light.
It turns out that orignal brass seals were quite thin, so that they would arc when under pressure of the nut, and bite into the spigot.
Thin PEEK however, arches too easily, and continues to comply and buckle, requiring several re-torques, with dangers of leaks in between.
The solution is to maximize the thickness of the seal to the insides of the nuts. This also allows for more support across the gaps between spigots and nipples.

Given the variation between spigots and even today's commercial nuts, custom-fitting gives the best assurance of a lasting seal, and re-useability.

On to the sealer for the nipples themselves, the host of the forum suggested Permatex's "The Right Stuff", and used it upon their 'signature' Anders knucks.
Although it warns agains use with fuels on the can, I fould it to survive miraculously in my immersion tests!


Return to Knuckles