thanks for your kind words,
i'm making header for subaru and up pipe and our header is little fragile i think. thick or thin, a lot brand subaru headers are still cracking. i just tried to minimize the risk, some other brands are using sch10 pipe too
i think you need to improve the purge side of things. its not that hard to get it completely silver on the inside.
also it looks like your pushing in filler. i would be inclined to do a root pass without filler, especially if you have no gap. then do a 2nd pass with filler. try not to push filler in.
try to keep it smooth on the inside and clean, which will help reduce cracking.
also it looks like your pushing in filler. i would be inclined to do a root pass without filler, especially if you have no gap. then do a 2nd pass with filler. try not to push filler in.
try to keep it smooth on the inside and clean, which will help reduce cracking.
tweak it until it breaks