lets get to the bottom of cracked custom exhaust manifolds

[acannell]

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.

[GLHNSLHT2]

You're probably doing ok because your flanges are held together.

[acannell]

You're probably doing ok because your flanges are held together.

that really does seem like it must be it..

for headers where the turbo gets located off in space somewhere and the turbo to block strut gets removed, the forces of 30lbs of turbo bouncing around on foot and a half lever are going to do some serious damage to hard welds. are most people bracing the turbo with a new custom brace or just letting it hang off the header? maybe thats the solution to this whole thing

even my crummy 89 jeep, which has a sort of tubular welded manifold stock, has a brace at the bottom of the manifold near the cat which bolts it to the engine (or tranny? I forget)...

[going4speed]

Are you back purging those welds? What amperage? Looks a tad hot to me.

[acannell]

Are you back purging those welds? What amperage? Looks a tad hot to me.

nope no back purging..it was about 2 1/2 years ago, I think the amperage was 60 to 90. I always ground it down and re-did anything that got contaminated or otherwise strange. The picture makes it look really hot because of the contrast I think. In person its very mild. There was almost never any burn through of significance.

[turismolover22]

Its not a stainless setup, so, even though it is desired, it's not necessary to back purge ifyou take care with your welds. Mild steel doesnt sugar like SS does.

[Chris W]

Our first generation welded header used the factory turbo support bracket. There just happened to be the exact same sized bolt about three inches to the driver's side which worked out great.

Chris-TU

[forcedfedmopar]

my header is doing well so far, but my turbo is supported by a bracket from the bell housing to the flange.