Intake manifold rivet air leak

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Intake manifold rivet air leak

Postby theknucklehead » Sat Feb 09, 2008 4:49 am

Can anyone out there tell me if there is a way to seal the rivets that hold the threaded manifold nipples to the head on a 1948 panhead motor. I just had the motor rebuilt and was doing a pressure test on the manifold and found that the rivets were leaking pretty bad. I am trying to do an accurate restoration so I have to use the rivets. Is there any product that I can use from inside of the intake to seal the rivets?
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Postby PanPal » Sat Feb 09, 2008 5:28 am

Peen the rivet. Any sealer will be subject to a bad seal down the road. You may need to replace the rivet to get it to seal correctly but metal to metal will be the longest lasting way to keep it sealed.
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Postby Cotten » Sat Feb 09, 2008 12:21 pm

Knucklehead!

Have you brought this to the attention of the rebuilder?

Ultimately, replacement of the rivet may be your best approach, although it is very difficult to reproduce the exact "upset" as the Factory. (I cannot etell from the photo if those are bubbles, or they have been replaced already.

You may want to review http://virtualindian.org/11techleaktest.html for tooling and sealer tips.

The only paint-on sealer that I have found to be P4gas-proof is an isocyanate urethane. I have sealed several casting porosities and micro-fissured with one used for water towers, with lasting results.

Good luck,


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Postby theknucklehead » Sun Feb 10, 2008 4:20 am

Thanks Cotton,
The rivets have been replaced. The builder tried to talk me out of them but I insisted on keeping it a original as possible, so in they went, ( if I survive this rebuild I am going to have the bike judged by the AMCA). I purchased some of the sealant you described for use on the fuel crossover parts. I will try to seal the rivet on the inside of the manifold. I'm wondering if we should have put a little JB weld on the rivet before inserting thru the manifold nipple.
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Postby Guest » Sun Feb 10, 2008 5:19 am

I'm sure with the expansion and contraction caused by heating and cooling, JB Weld would leak air. I had massive intake leaks on my 51 which made for hard starting etc. Don at Headhog welded up and re-threaded the intakes. When I installed the new nipples I used a little steam pipe thread compound which I'm hoping will stay somewhat pliable during repeated heat cycles. After one year the intake tested out with no leaks. As far as sealing the rivets, I had Don weld the holes up to eliminate that leak ,since my bike is far from correct anyway. Mike
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Postby jellero » Sun Feb 10, 2008 7:17 am

i'm a big fan of high temp silicon when putting the intake together. j
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Postby 108 » Sun Feb 10, 2008 7:17 am

I also have a '48 Pan but it has always had threaded studs from the inside the nipples with castle nuts and cotter pins on the outside. Were these a later HD design or aftermarket parts ? they have never leaked.
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Postby mbskeam » Sun Feb 10, 2008 2:10 pm

because I dont know, what do these rivets do?
besides leak....LOL
this is a real ?

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Postby Cotten » Sun Feb 10, 2008 3:35 pm

Jellero!

Please test your silicone sealer in modern fuel; If you live in the USA, you are running with a lit fuse.

Mike!

The rivets are there to prevent the nipples from backing out upon loosening of the nuts for service. It should be obvious to all that after years in service, the fine threads of the nuts and nipples can get frosty. (Anti-seize compounds were not prescribed in the service manuals, but they are our best hedge against time!)

The most common cause of leakage is stress from over-tightening of the nuts in an attempt to make the unforgiving brass ferrules seal, even when properly annealed. Brass was the best our forefathers had. We enjoy spaceage alternatives today, allowing the assembly to seal with much less force.

Back to rivet replacement:
Seal-Lock "Fluid-Weld" http://silver-seal.com/ is specifically made for peened metal-to-metal adhesion, forming a chemical bond between dissimilar metals.
I first learned of it when "pinning" cracks in castiron engine blocks. (This is a process where a crack is repaired by drilling and tapping into the crack so that a tapered threaded plug can be forced in and peened. Then another hole is drilled and tapped into the crack, overlapping the previous plug. The process is repeated over and over until the entire crack has been stitched up.)
And as it is a permanent bond, it resists heat and solvents.

T'aint cheap, though!

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Postby theknucklehead » Sun Feb 10, 2008 7:53 pm

Thanks Cotton,
As always, you have probably forgotten more information on this stuff than I will ever know.
I will order some of the "seal lock" and let you know how it works. I tried some high temp two part epoxy around the head of the rivet, inside of the manifold, and it still blows more bubbles than Krusty the Clown.
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Postby Cotten » Mon Feb 11, 2008 2:34 am

The Knucklehead!

I take it that ol' "Crusty" was the rebuilder?

A professional would want to 'make good' on it. He should be given the opportunity.

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Postby Guest » Mon Feb 11, 2008 3:07 am

Cotten, you're correct. He is a fantastic motor and tranny guy, (and a very CRUSTY old biker). The problem is , as a fantastic builder he is also slow and very busy. I hate to bother him with something that I may be able to fix myself with a little help from friends on this web site. I always look at this insanity that we call a "hobby", as a learning experience. It always means alot more to me, and I am sure to others that use this web site, when I build or re-build something on my own or learn how to fix a problem myself. As an old biker friend once told me years ago, "it's the journey that counts, not the finished product". I will call him tomorrow, as he is a friend, and ask his opinion.
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