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White Stay-Silv flux any use in brazing cast iron?


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Old 10-11-2015, 04:14:12 PM
sdowney717 sdowney717 is offline
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Default White Stay-Silv flux any use in brazing cast iron?

I need to repair Onan Exhaust and intake manifolds which are cast iron.
I cleaned all the rust off using vinegar. I need to reattach broken ears for the bolts.
I am going to bevel them back a little and fill up with white fluxed brazing rods. I was also wondering is smearing on the Stay-Silv would be of any use? I would like to coat over some of the cast iron on top with braze, especially around the exhaust hole where it just rusts.

---------- Post added at 04:14 PM ---------- Previous post was at 04:02 PM ----------

One broken ear, I plan to fill with braze.


This lower part will rust again. And I need to add a little braze buildup to the bottom of the exhaust side, it is no longer flat with the intake port, the gasket surface has rusted away so there is too much space. I figure that is good for the future as bronze wont be rusting away like iron. Block exhaust port is ok being even with the intake port.


I have found that smearing Permatex silicone gasket maker Hi heat versions ( I used orange copper) keeps the cast iron dry and stays on the hot metal.

The exhaust manifold has 3 broken ears which I need to reattach. Plan to bolt them onto the intake and braze them in place so they sit flat.
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Old 10-11-2015, 04:45:23 PM
Roland Hayes Roland Hayes is offline
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Default Re: White Stay-Silv flux any use in brazing cast iron?

I normally make these kinds of repairs with just braze/bronze weld, I build up the whole missing area of metal with the filler rod then after cooling I file it back into shape and re-drill the hole, like this the repair is a lot easier to make and strong. After painting the color difference between the brass/bronze and the iron is invisible.
I've built up some very highly stressed parts like this including clutch release mechanisms and never had a repaired piece fail.
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Old 10-11-2015, 06:55:44 PM
sdowney717 sdowney717 is offline
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Default Re: White Stay-Silv flux any use in brazing cast iron?

The exhaust manifold bolts on top of the intake manifold flange.
I was thinking to smoke the surface with the torch.
Grind back a wedge like space on the ears.
Then bolt the broken ears down with manifold in place.
Fill the space with braze.
Then flip it over maybe grind a groove and fill that side.
Then file it flat.

It is a 2 cylinder engine, so I am only showing one side. Manifolds span across motor top to each cylinder, so keeping it all flat is critical to good positioning.

This is a salvaged generator that was destined for scrapping, so no one cared much about it when tearing it from the boat, an Onan MCCK 6.5 from early 1970's, somehow they broke these parts.
Marina owner knows me and I got it free for parts, but decided why not make it run again. I took it to pieces and built it back up, this is the final repair needed.
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Old 10-11-2015, 07:29:25 PM
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John Tice John Tice is offline
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Photo Re: White Stay-Silv flux any use in brazing cast iron?

At my shop we TIG weld cast iron with silver solder, works great.



JT www.smallenginemachineworks.com

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Old 10-16-2015, 02:29:03 PM
sdowney717 sdowney717 is offline
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Default Re: White Stay-Silv flux any use in brazing cast iron?

Got both manifolds done with the braze. Worked out well IMO. I ground the cast iron using a grit blade first.
One side reattached ears


other side. Basically you really should braze against the mating surface bolted down to make sure things fit well. I tried brazing the ears on top of the table saw which was ok, but the ears lifted a little so had to bolt it down, reheat real hot and tighten the bolts, then the ear moved flat.


The broken out ear filled with braze.


I built up the rusted away bottom of the exhaust port on the intake manifold both side.
Was not easy then to reface flat to the intake port. I used my table saw and some coarse sand paper and by hand ground it against the flat surface till it fit perfectly to the engine block. Sand paper really does good job removing braze. I simply ground only the brazed port bottoms. Then lightly ground together. with intake port. Sat flat on the table saw no rocking when I was done.





How they bolt together.
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Old 10-16-2015, 02:32:50 PM
sdowney717 sdowney717 is offline
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Default Re: White Stay-Silv flux any use in brazing cast iron?

Nice fit for the flanges


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Old 12-29-2015, 06:22:55 PM
sunshineman sunshineman is offline
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Default Re: White Stay-Silv flux any use in brazing cast iron?

Hi there ,
I repair automotive componets for a living , welding is the best optoin for manifolds, oxy , tig, or stick.any home handyman can do a basic repair with a small stick welder using nickle iron .it is easy to file , shape and wont rust like your manifold did .prep metal with carbide cutters (grinding rubs impurities back into your work) heat with oxy in area to be welded untill dull red, this is to pull all remaining impurities out of of the area to be repaired.dont try and reattach small parts , eg take your repair past bolt hole , so when your finished you drill the hole in only weld .hope this helps someone in a resto project
Regatds sunshineman
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