Throw that thing in the oven at 650 for a couple of hours. Then take it out and clamp it down flat to a preheated steel table. By the time it cools all the the molecules will be inline again

 

so I took it to the machine shop and put the manifold in a 50 ton press. now it is fairly close less than 1/32" off. the shop will face it. then I'm going to bolt it to a iron plate with old gaskets and aneal it in our vacuum furnace at work.

so how hot do I need to get to stress releive mild steel?

 

until it glows

 

bright orange to bright yellow if its general steel. white hot is abit much.

depends on what exactly it is, how hot, how long and what you're trying to do.
if you're trying to do low temperature stress relieving ive heard 1000*F'ish for 24 hours+ will do it. Must be high 500's and it can take a week at that low of a temp.
if you half way anneal it 1300-1400*F.
all the way 1400-1500*F.
let it cool slowly to room temp.

 

next time skip around,and wait in between runners, sounds like you welded solid from one side of the flange to the other.

 

Sounds like he welded w/o it bolted to anything. Even a pro can't comepletely eliminate warpage if the steel is allowed to move around. You're probably best off doing it with the furnace anyways, since enough heat cycles and most eventually fail (might take years, but they will). The place I worked at had every piece we machined stress relieved after it had welding done to it. They were also dealing with mil-spec crap like rotor hubs for Blackhawks.

 

My favorite are the places that want you to lay a 1/2"+ bead on .035 wire running 600-700"/min. Or the places that will give you raw stock cut / pressed like you want it, full of scale and DRENCHED in semi-dry to dried cutting fluid. Then not want you to take the time to clean it & grind the scale & rust off.

Titacular!