how about a thread with as much hard data as possible about custom exhaust manifold (tubular) with cracks (or not)
please lets keep it to things known for sure..i.e. if you second brothers sisters cats dad welded up something and it cracked sometime in the mid 90's thats probably not helpful lol
heres my datapoint:
skill level of fabricator: beginner..basically the first thing I ever welded up with my TIG welder..no attempt made to control stresses
material: mild steel
thermal coating: none
peak measured EGTs: probably 1700F to 1800F for a few seconds max measured about 2" from head on #4
welding method: TIG (Argon, ER70S-2 filler)
tube to flange welds:
where the primaries and big tube meet the flanges, they are pressed into the flange so the edge is at the open side, then hammered against the flange wall and the edges welded together
also, small tack welds are put from the tube to the flange on the other side of the flange
primaries length: about 14" each
primary tubes OD/ID: 16 gauge (.059" wall) 1.5"OD
big tube from collector to turbo flange: 18 gauge (0.049" wall) 2 3/8" OD
head flange: FWD performance about 1/2" thick mild steel, looks water or plasma cut
turbo flange: same as head flange (or did I get it from TU? either way its the same material/thickness)
collector style: custom 4 to 1 into larger
supports: two 1/2" steel bars connecting the flanges together
usage: about 10,000 miles/2 years of daily driving and stock to 22psi, no racing.
status: no cracks visible and I've had it out several times. no exhaust leaks heard.