See if you guys can help me out here.

i bought a bunch of wastegate flanges from Mopac. I tapped them with 5/16" coarse. I used one on a log style manifold. Everything was fine. Resurfaced the flange after welding, ran a tap back thru it to make sure everything was ok.

So i installed this guys kit, and within a week one of the bolts snaps. Ok, center punched it perfect, drilled, re tapped. I nailed it perfect. So i install a stud. And grade 8 hardware. A couple weeks later we go to take the wg off and the other bolt won't come out more than a couple threads. SNAP! Ok ****. Re drill, tap, and put another bolt in. Same damn thing happens again so i decide to take the manifold off, cnc the flange off and weld a new one on. Used 12.2 alloy cap screws. So i do that and so far so good.

So I build another manifold for someone, equal length this time. Welded, re surfaced, re tapped to make sure everything is good. So I install it with the 12.2 cap screws. A couple weeks later one of the bolts falls out. Guy brings back the car, i go and get alloy lock washers and another bolt. So I go to take the other bolt off and it won't come out more than 1 turn. It won't tighten back in either lol. It seems as thought the material the flanges are made of are degrading fast due to cycling heat or something, some kind of inferior steel used?

WTF can be going on here!!!!!

 

Oh, these are 3/8" mild steel flanges.

 

It may be a good idea to normalize the metal after welding and machining.

 

Just an fyi you should normalize after welding but before machining, as stresses in the metal may cause it to change shape during normalizing.

 

install the bolts or studs using a good coating neversieze