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Thread: just covering the bases

  1. #1
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    Default just covering the bases

    Asked on the "other" vintage site about intake manifold nut and brass seal angles. A fellow over there was kind enough to post a pic showing the direction the angle is swung from. Now I'm wondering if I could get a little better seal if I altered the angle in the nut to make it a little steeper, so that, in essence, the angle on the nut would "bite" a little closer to the thinnest area on the brass piece. Any thoughts from anyone?

  2. #2
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    Quote Originally Posted by Omarttentmaker View Post
    Asked on the "other" vintage site about intake manifold nut and brass seal angles. A fellow over there was kind enough to post a pic showing the direction the angle is swung from. Now I'm wondering if I could get a little better seal if I altered the angle in the nut to make it a little steeper, so that, in essence, the angle on the nut would "bite" a little closer to the thinnest area on the brass piece. Any thoughts from anyone?
    When you say "better seal", Omar,

    Does that mean you have leaks?

    Since brass seals are temporary, and the nuts do not wear out, wouldn't it make sense to carve new seals instead?

    We know the nut forces the seal harder upon the face of nipple than the spigot.
    And yes, a higher angle of nut bevel contacts lower upon the seal, tranferring the force toward the spigot where it is most needed for hard brass.
    Used OEM brass seals are usually arched a little, and their bevel crushed, as you would expect of a torqued metal compression ferrule.
    Often they are crushed to the point of difficult removal, even damage to the spigots.

    We know the OEM angles worked for OEM brass seals, and genuine H-D nuts averaged 57-59, but without genuine NOS rings accurately measured and averaged, I would be conjuring to guess any designed interference.

    So I avoid brass.

    ....Cotten
    Last edited by T. Cotten; 06-06-2019 at 05:26 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  3. #3
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    Default

    I'm thinking there is a leak. Fixed a loose intake nipple in the rear head. As a consequence of this, the rear intake nipple is screwed into the head deeper than the front one. Now the gap between the manifold pipe and the nipples is bigger than it was before, and the manifold is incorrect for the motor (only 3.25" long) The owner bought PEEK seals, but I'm thinking they are located too far out on the manifold. Had the owner purchase a repop manifold from throttle masters. It comes with brass seals. I'm gonna anneal those seals when it comes in to soften them, and use them before I put the PEEK seals back in. That would preclude the fact that the PEEK seals fit the new manifold. I did notice during the rebuild that the angles on the nuts are rough as a cob, so I thought I'd chuck them up, indicate them in, and put a better surface on the angle face. I'll keep you apprised.

  4. #4
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    Quote Originally Posted by Omarttentmaker View Post
    I'm thinking there is a leak. Fixed a loose intake nipple in the rear head. As a consequence of this, the rear intake nipple is screwed into the head deeper than the front one. Now the gap between the manifold pipe and the nipples is bigger than it was before, and the manifold is incorrect for the motor (only 3.25" long) The owner bought PEEK seals, but I'm thinking they are located too far out on the manifold. Had the owner purchase a repop manifold from throttle masters. It comes with brass seals. I'm gonna anneal those seals when it comes in to soften them, and use them before I put the PEEK seals back in. That would preclude the fact that the PEEK seals fit the new manifold. I did notice during the rebuild that the angles on the nuts are rough as a cob, so I thought I'd chuck them up, indicate them in, and put a better surface on the angle face. I'll keep you apprised.
    Omar!

    Please bubble-test, as discussed at http://virtualindian.org/11techleaktest.html, and then there is no thinking there is, or hoping there isn't.

    Unless the owner bought my services, the PEEK seals are probably mass-produced.
    PEEK requires different dimensions than brass, and must be mated to pristine manifold spigots, or they will not be re-useable.
    The fit must be a tight, squeeze-on assembly, and not just at a molded flash-line inside.

    I have EL manifolds running successfully upon customer's FLs properly fitted, so PEEK can overcome nipple spacing and alignment issues.
    (Brass would be far more difficult, if not futile.)

    If you don't get bubbles with the new brass assembly, you are good to go.
    But beware of enormous variation in nut bevels and seal angles of modern productions, even from the same manufacturer.
    This alone accounts for some mass-produced PEEK seal failures, and it can't help brass, either.

    Good luck!

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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