I have hit a small snag. Driving through Laos we hit a large rock (with 6 people in the car) and now have a suspected cracked exhaust manifold (75 TS). Has anyone had success welding them? A replacement would be the obvious choice but not so easy at this stage. I haven't managed a good look yet but initially it appears to be where the manifold mates with the first stage of the exhaust.
Thanks
Julian
They can be repaired, but it's a rather tricky process.
I have tig welded cracked cast iron manifolds before, the area each side of the crack needs to be pre-heated *just right* and cooled correctly, otherwise 30 seconds after finishing the weld you'll hear a little ping noise as it re-cracks in a slightly different spot :(
There is special mig wire and arc rods available for repairing cast iron, but they're getting close to the price of a new manifold.
You'd probably have a lot easier time brazing the crack rather than welding though.
As long as you're not running the engine so hard that the manifold starts glowing, brazing should hold up ok.
If it was a turbo manifold or your engine saw much dyno time, I'd give brazing a miss because the manifold could potentially get close to the filler material's melting point.
Laos?????? :o
Beetle,
You haven't been paying attention
http://www.alfaclubvic.org.au/forum/index.php?topic=10598.msg65159#msg65159
Julian,
You are in S.E. Asia so ANYTHING is possible ;D. I know Thailand has a burgeoning classic car scene, not so sure about Laos though. If you can't source a replacement, I'd seek out a local welder and have them carry out a repair (I'd also go brazed) and maybe think about adding some strengthening pieces.
Alternatively, a locally manufactured set of steel header pipes might not cost a lot to have formed and welded up........... ;)
If you have no intention of keeping the car in the long run, just get a decent mig weld on it and it may last.
Thanks for the comments guys. I am going to try getting it mig welded and hope for the best. It just needs to get me through this trip and when I get it back to Australia I'll replace it. Or, I will buy a good set of headers for the 75 and then swap them over to the GTV (Alfa 911) when I get back :-)
Julian, I see you are forced to go back to Singapore? You should be able to pick up a set of either stock or aftermarket headers there or in Malaysia. With what you have planned I'd be looking at getting a new manifold instead of welding it, if at all possible. If it cracks again (likely) it will be noisy and possibly a fire risk, which will spoil the trip. Get onto the Singapore or Malaysia Alfa club(s) if you can. In my experience Alfista are the same all over, regardless of their native language, and someone will help out..
To weld cast iron you have to get cold cast arc rods ... VERY expensive ... about $700 a packet here ... and you can weld a tiny bit ... wait till you can touch it ... then weld a bit more
Option 2 ... heat the cast till cherry red ... then use low hydrogen rods ... cheaper but harder ...
Mig and Tig don't really work ... you can botch stuff up but it's not a good solution,
You can tobin bronze braize as a temp option too
Happy to donate the manifold you need so longas you dont mind forking out for the shipping!