Thread: Silver solder cast iron?

I have a CI cylinder head from an old motorbike. It's very used and had got some damage. This included broken fins and a threaded boss that had snapped off. These have been repaired by brazing and machining.
But, it needs some more repair - a steel stub tube in its exhaust port, for fitting the exhaust pipe to.
This is normally a press fit and a pin tapped into a hole drilled in from the side. All that's been destroyed, no doubt because the pin wasn't noticed by whoever removed to old stub.
I thought I'd braze a new stub in, but I'm now worried that the previous braze repairs might melt. Clearly, I'm no expert.
Maybe silver solder could be used as alternative to brazing rod? It melts at a lower temperature.
Questions:
Am I too worried, and brazing would be OK, as it's about 2 inches from the nearest previous brazing repair?
Would silver solder hold up to the heat of exhaust gases?
Would it be strong enough for this?

Any advice happily received.

Jordan

Originally Posted by nadroj

I have a CI cylinder head from an old motorbike. It's very used and had got some damage. This included broken fins and a threaded boss that had snapped off. These have been repaired by brazing and machining.
But, it needs some more repair - a steel stub tube in its exhaust port, for fitting the exhaust pipe to.
This is normally a press fit and a pin tapped into a hole drilled in from the side. All that's been destroyed, no doubt because the pin wasn't noticed by whoever removed to old stub.
I thought I'd braze a new stub in, but I'm now worried that the previous braze repairs might melt. Clearly, I'm no expert.
Maybe silver solder could be used as alternative to brazing rod? It melts at a lower temperature.
Questions:
Am I too worried, and brazing would be OK, as it's about 2 inches from the nearest previous brazing repair?
Would silver solder hold up to the heat of exhaust gases?
Would it be strong enough for this?

Any advice happily received.

Jordan

Braze away to your hearts content. I have never seen a braze repair melt due to another repair nearby and in fact, when I have tried to melt a brazed joint to separate components it took a serious effort.
Naturally, you will want to evenly heat and cool the whole thing, possibly even consider using a bath of Lime to slow cooling down.

Thanks Karl, that's reassuring.
By lime bath, do you mean like powdered builder's lime?

Jordan

Yep, just plain old builders lime. Just pour some in a suitable tray, drop your head in it and pour more on top to cover and insulate it totally.