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Solder for copper primer lines

Posted: Sun Jan 15, 2023 12:53 am
by Vertical
I'm having trouble finding info on the proper type of solder to use for this. Specific location is the the soldered brass bulb/sleeve fitting where it attaches to the intake manifold jet.

I have various electrical and plumbing solders around, but leaning towards some that's 6% silver and acid core. Specs say application temp 400-700F.

Any recommendations?

Thanks!

Re: Solder for copper primer lines

Posted: Sun Jan 15, 2023 12:30 pm
by Bruce Fenstermacher
I've used what ever I picked up of my bench which would have been some type of solder I would also use for electrical. I've never had an issue and really never thought much about it. Wonder what really fancy solder they used in the '30s and '40s to make the same connection on my A-65? Bet the same stuff in the '50s. And I'd be surprised to find it wasn't anything but the cheap stuff from the local hardware store.

Re: Solder for copper primer lines

Posted: Sun Jan 15, 2023 12:36 pm
by GAHorn
Ordinary solder will do the job at around 600-degrees, but Brazing silver-solder is the strongest and withstands higher heating: https://www.amazon.com/Harris-Safety-Si ... 05&sr=8-17

Re: Solder for copper primer lines

Posted: Sun Jan 15, 2023 2:17 pm
by redacted
Silver all the way, 56% or whatever. Otherwise it won’t stick.

Re: Solder for copper primer lines

Posted: Sun Jan 15, 2023 5:01 pm
by Vertical
Hmm. That's quite a variety of suggestions. I've never silver brazed before, but I'll do some research.

Thinking out loud...I suppose the absolute worst case scenario would be priming a hot engine and having a failed joint spray fuel on the exhaust..

Re: Solder for copper primer lines

Posted: Sun Jan 15, 2023 7:05 pm
by hilltop170
Silver soldering is NOT the same as brazing and requires special solder. It is good for joining copper and brass but requires higher heat than lead solder plus special flux and the joint surfaces must be absolutely clean and completely fluxed for the joint to hold. It is much stronger than lead solder if done properly but is easy to overheat the work. Practice on a similar joint and get competent before trying to solder the actual parts.

Re: Solder for copper primer lines

Posted: Sun Jan 15, 2023 10:33 pm
by cessna170bdriver
Vertical wrote:Hmm. That's quite a variety of suggestions. I've never silver brazed before, but I'll do some research.

Thinking out loud...I suppose the absolute worst case scenario would be priming a hot engine and having a failed joint spray fuel on the exhaust..
There’s no need to prime a hot engine.

Re: Solder for copper primer lines

Posted: Mon Jan 16, 2023 12:27 am
by redacted
I just fixed a primer line last week during annual. cleaned the line with sandpaper, flux, slid the piece into place, hit with mapp gas torch, silver solder. done. not rocket surgery here, just silver. metallurgy is neat!

Re: Solder for copper primer lines

Posted: Mon Jan 16, 2023 3:42 am
by Vertical
cessna170bdriver wrote:
Vertical wrote:Hmm. That's quite a variety of suggestions. I've never silver brazed before, but I'll do some research.

Thinking out loud...I suppose the absolute worst case scenario would be priming a hot engine and having a failed joint spray fuel on the exhaust..
There’s no need to prime a hot engine.
Uh oh..I guess I've been doing it wrong.

Re: Solder for copper primer lines

Posted: Mon Jan 16, 2023 12:36 pm
by Bruce Fenstermacher
The key to soldering using lead or silver is a clean joint. Have yet to have any luck with silver but I don't practice/experiment either. Go with what you know.

Re: Solder for copper primer lines

Posted: Tue Jan 17, 2023 1:44 am
by Vertical
Ordered some Harris Stay-Silv 45 and matching flux. Watched a few youtube videos. Doesn’t look any different than soldering plumbing fittings.-Just higher heat.