Board index Flathead Power-Technical Questions, Answers, and Suggestions Knuckles Intake Nipple Question

Intake Nipple Question

Moderators: Curt!, Pa

Post Mon Aug 05, 2013 7:42 pm

Posts: 1643
Location: Interlaken, NY USA

Greetings, I'm about to undertake a nipple replacement fix for my buddies 41 knuck. Sometime in the past, aluminum "o"ring nipples were inserted. He can't get them to seal, and wants them out and threaded types put back in.
The problem is, I just got replacement nipples, Colony, and they came with what appear to be aluminum rivets. Shouldn't they be Iron? Anyone know where I can get the proper rivets? (Cotten, are you out there?)
Thanks in advance,

Post Tue Aug 13, 2013 6:33 am

Posts: 636
Location: Wisconsin, USA
Dick, Rivet fit is important for a good seal, size your rivet holes true and make your own rivets from grade 3 or lighter hardware. I always shoot for plug to a half thou of interference fit.

Post Fri Aug 16, 2013 6:53 am

Posts: 3011
Location: Central Illinois, USA

Sorry for the late reply, but this site's format only accepts one of my PCs that I rarely use.
(Even then, I cannot type in a reply; I must cut'n'paste from Notepad!)

As Kyle noted you will want to ream the holes and custom-cut rivets for a press fit.
This will allow them to only require a simple "uspet" of the exposed portion, rather than ugly peening.
Knucks are brittle, and prone to splitting, so setting the new rivet demands care.

I use anvils with a ramp cut into them to push the rivet outward, as shown a
The easiest way I have found is to hold the anvil in a vise, slip the head over it and then twist to hold the rivet's head firmly, and then smack the exposed end with a hammer in my free hand.

The most difficult aspect to seal is between the shoulder of the nipple, and the thin raised lip upon the casting.
If this lip is blemished, it might be dressable; If it is damaged, it must be repaired.

Last edited by Cotten on Sat Aug 24, 2013 12:40 pm, edited 1 time in total.

Post Sat Aug 24, 2013 11:30 am

Posts: 2677
Location: Los Angeles, CA
I use anvils with a ramp cut into them to push the rivet outward, as shown a

The webpage cannot be found
HTTP 404
Most likely causes:
•There might be a typing error in the address.
•If you clicked on a link, it may be out of date.

Post Sat Aug 24, 2013 12:46 pm

Posts: 3011
Location: Central Illinois, USA
Thanks Chris!

Right this minute I can type in like the wind to the forum upon an old WIN98 Gateway, that is actually stuck in 'Safe Mode', whereas my 'good' PC cannot browse the site properly.

And I can edit!

Sorry for any confusion Folks,

See anybody at Davenport?
It shall be typically hot and humid....


Post Sun Aug 25, 2013 8:25 am

Posts: 1643
Location: Interlaken, NY USA

Thanks for the input guys, roger on making my own rivets. I presume just turn down cheap hardware store "no mark" bolts to get the rivet stock, and cut them so they just stand proud of the cylinder head. I figured I'd be pulling the heads to do the repair, rather than in situ. I've seen the virtual indian site before, looks like the anvil has a slight taper to fit inside snugly, and a flattened side that is blended into the rest of the body, so that one places the anvil in place, with the flat towards the rivet head, then rotates till the rivet is firmly backed up by the anvil. That about got it right?
I think I'm going with JB weld to seal them in place, I've got it and and have had good results with other repairs using it.
I'm figuring some light filing and fitting to get a good match to head and nipple, sound good?

Post Sun Aug 25, 2013 11:39 am

Posts: 3011
Location: Central Illinois, USA

Yes, the anvil is just a cam that pushes the rivet like a tappet.

I used JBWeld for many nipple replacements, all successfull, so far.
The caveat will aways be the P4gas.
My immersion tests last year showed that JBWeld requires several weeks of cure to achieve its optimum resistance.

Our Forum Host uses Permatex's "The Right Stuff".
Even though it has a fuel warning on the can (!), it survived miraculously well in immersion tests upon etched glass in last season's local fuel.

I have been too distracted to test this year, but just one season's success marks it as a most unusual off-the-shelf goober, in that it is not a hard compound, as others that resist most fuels are.

Good luck!


Return to Knuckles