Hello, Cast Iron Exhaust Manifold Repair
Posted: Fri Nov 06, 2015 10:45 pm
I want to try and repair this cast iron exhaust manifold from a 1971 477ci Ford Super Duty dual axle grain truck. The previous owner attempted a repair while the manifold was still bolted to the engine. We tried but could not locate replacement manifolds or headers. After the manifold was removed it was sand blasted.
The 3 types of tig filler wire I considered to use were: Aluminum Bronze, Crown Alloys Royal 55/45-10 copper - nickel, or a new product by Davbro Inc. EZ WELD tig wire.
The manifold was broken in 3 parts and also has a vertical crack in it.
Has anyone attempted a repair like this? and what would be the method that would be most successful to use.
I was unsuccessful trying to tig this manifold. The excess silicon and carbon in the manifold would pop off and coat the tungsten. What I discovered after drilling a hole at the top and bottom of a crack was the shavings coming off the drill bit looked like black granules of gunpowder no metal spiraling up the bit at all. I think this manifold had a lot of slag in the molten metal when they poured it into the mold during manufacturing.
I ended up brazing it with Crown Alloys 120 nickel/silver brazing rod.
There was a large hole in the manifold so I brazed a 1inch by 1 3/4 inch plate on the inside of the manifold before I reassembled it.
After all the work and brazing, the end exhaust port is warped up 1/8 inch, so when we bolt it back on the engine a shim will be needed to get it to seal up. If nothing else I learned a lot from this project. 
I guess I will have to learn how to make a set of headers 
- manifold_2.jpg (90.42 KiB) Viewed 728 times
The manifold was broken in 3 parts and also has a vertical crack in it.
- manifold_3.jpg (115.99 KiB) Viewed 728 times
I was unsuccessful trying to tig this manifold. The excess silicon and carbon in the manifold would pop off and coat the tungsten. What I discovered after drilling a hole at the top and bottom of a crack was the shavings coming off the drill bit looked like black granules of gunpowder no metal spiraling up the bit at all. I think this manifold had a lot of slag in the molten metal when they poured it into the mold during manufacturing.
I ended up brazing it with Crown Alloys 120 nickel/silver brazing rod.
- Bolt lug brazed back on
- cornerpiece.jpg (36.29 KiB) Viewed 638 times
- Finished manifold
- brazedmanifold.jpg (33.68 KiB) Viewed 637 times
- warped now have to shim it
- warped.jpg (41.11 KiB) Viewed 637 times