bare bronze welding cast iron

If you happen to have a some what rare car, or one that is simply thirty or more years old, you may find that if you ever crack your manifold exauhst that you can not get another by simply going to a (pick and pull) So, the first thought is..most of the time, "I will simply zap it with NIRod". WRONG! an old manifold that has repeatedly heated and cooled is very brittle and the sudden change in temp and too rapid cooling may crack it even more. Now what i do is use bare bronze rod and braze the crack. Here is how i do it. First I find the ends of the cracks and drill a 1/4 hole half way through the material at each end of the cracks. Next I use a rose bud torch and heat up the cast iron as evenly as possible peening with a hammer lightly to releive stress in the casting. After about five minutes of this I quickly switch to a oxy-actl. brazing tip and start my pass. The first thing i do is heat up as much of the crack as i can to cherry red and sear one coat of bronze using plenty of flux. Then I start at one end of the crack and fill in the crack that i had previously veed out with a grinder to half way of the depth of the material and no more than 1/4 inch wide. I use an overlapping spot weld like technique. i lay a small amount of bronze, remove heat for a second and overlapp where i left out. When done I have a bronze brazing weld with no undercut or cold roll. Then i use the rose bud again for some post heating gradulay reducing the heat and peening with hammer again. Then I quickly take the whole peice and cover it in powdered lime so that it cools very slowly. This will stop it from cracking due to rapid cooling. Also it may put some ductility in the cast iron. It takes about four hours to be cool enough to touch with the bare hand. Then I grind the bronze weld flush and inspect the weld to see if i got proper bonding, all you should see is a ribbon of nbronze that has no porosity or cavities. I have also done rare boat manifolds like this when repeative NIRod was used at other shops and they broke every time. Still no 100 percent with cast iron like this. Sometimes it just cracks more, after all it is a dirty porous metal that is very brittel. Anyway, i have had very good luck doing it this way

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beserker (author) 5 years ago
I apologize to everyone for my sloppy writing. I am tecno challanged and do not have a digital camera nor would i know how to download pics or even operate the darn thing. Not only have I posted in the wrong area, but i have not presented this in the correct format for this website. i just thought I would give soemthing back after getting some very useful info here. i hope it helps some one despite no pics and posting in the wrong place.
Kiteman5 years ago
You ought to write up a proper instructable on this.

One with paragraphs.
beserker (author)  Kiteman5 years ago
Did i leave something out other than proper paragraph format?
Materials, tools, safety tips, and photos.

You've also posted this as a forum topic, not an instructable, so you'll lose a huge number of potential views by having it in the wrong place.
Pictures would be cool too :-)