Originally Posted by skidude108
How is making a quality manifold out of mild steel selling a car with problems? Aren't most of the cast manifolds around here something other than stainless? The $200 price was an estimate, I don't think either of the flanges from JGS are stainless, and those tend to be tough to find. Is a SS manifold with MS flanges a bad idea?
Ive done it on my downpipe but that was about 2 feet pre cat i switched over to 3" mild steel from 2 1/2" SS. Now there are major differences in heat cycles the latter being the manifold. Constant heating and cooling espicially with dissimilar metals (although the only difference is 12+% of chromium/nickel) can potentially
create problems down the road. OTOH its not like your joining cast iron and stainless using FCAW. If it were me i would make it all the same metal.
A few quick questions about the previous manifold.
2. Did the "good" welder back purge while welding?
3. What welding process did he use?
4. Did he get full penetration?
5. What filler rod?
6. Where does it crack?
1. If its thin **** it is more prone to crack than say schedule 40 pipe
2. Without a back purge you are burning the chromium out of the metal creating the *sugaring* which will in turn cause stress risers and crack.
3. Im just curious on this one
4. Without full pen the pipe will already have stress risers in the weldment and be more prone to failure.
5. Im assuming your using 304 base metal since thats the cheap **** everyone buys (it works great for this crap) Important to know what kind of filler rod he used. I use 308L which is low carbon rod which aids in preventing martensetic. Martensitic is a property of alloys that allows them to be hardened but the downside it takes away from ductility.
6. If the crack started at the weld then most likely the stress riser gave way. We all know about thermal expansion and you add 1 flaw... time makes fools of us all right?