round pipe to oval ports. to bend or not to bend? that is the question!

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hello all, as the title says; i'm doing up a turbo manifold and have some 1.5" sch 10 304 butt pipes which are, of course, round going to the flange which has oval ports.the question is; can I bend them to match the openings and how do I do so properly without weakening my pipes.details you probably need; TIG, argon 100%, 1/2" mild flange, 309L filler with back purge. here's a pic for clarity;the other flange is a 3/8" mild. thoughts?
Reply:Tough call..You won't weaken anything..Maybe just grabbing 1/2" and squeezing in a vice untill you get close?It may work but keep an eye on your orientation.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Should I heat them or bend in a press? I'm wondering if that is why the 1/2" flange was beveled. They came as a package with the flange and butts...hmmm.
Reply:No heat required..You could also get them to co-operate with a good solid rubber hammer..Strange how it's one kit but......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:yeah it's not off by much, maybe a 1/4 or so. me thinks me crush a wee bit.u da man zap!
Reply:one more question, i've read, here and elsewhere, to do one root pass with no filler and one on top with.what do you think?
Reply:From the tube to the plate yes..Fuse then fill..Microzone would have some answers also..He does this stuff all the time.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I routinely shape piping to fit T3 and T4 flanges and other things. You can do it just pick a tool that will do it with some finess - a press, hydraulic bender, etc. One pass filler only here. I do hundreds of these a month ( in both SS and aluminum ) and they are vacuum tested, no leaks.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Thanks for the reply! Do you back gas or preheat before welding?
Reply:Back gas on thick plate is not needed IMHO...No preheat either..Just do it!...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterBack gas on thick plate is not needed IMHO...No preheat either..Just do it!...zap!
Reply:Niether heat for bending or welding is required..However heat is needed for hot-dogs burgers and sausages..I need to get the grille going.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Squeeze them in the vise. No big deal. 1 pass, no preaheat, 50-60 amps, only as much filler as is absolutely necessary.
Reply:Originally Posted by CapnbondoSqueeze them in the vise. No big deal. 1 pass, no preaheat, 50-60 amps, only as much filler as is absolutely necessary.
Reply:That flange is probably heavy with all the extra meat between mounting holes. . . .And I know that logs work, but they do just that, work, and not very well.  Try re thinking the manifold design so cylinders 1 and 4 aren't firing directly at eachother.
Reply:just a thought... I'd weld all the pipe together while you can get to the butt joint easily.    then I'd oval them a bit with a press.   then I'd make sure they all were flat in a plane with a grinder etc... (and fit up noice with the plate).   then I'd weld them to the plate.but i never have done such a thing.  so it's just an idea to kick around.
Reply:Originally Posted by m R g S rThat flange is probably heavy with all the extra meat between mounting holes. . . .And I know that logs work, but they do just that, work, and not very well.  Try re thinking the manifold design so cylinders 1 and 4 aren't firing directly at each other.
Reply:actually for a Mazda Miata. we're bringing this one from the dead but that's cool. I ended up bending all of them in my press, welding the fittings together, welding the log to the flange THEN the turbo flange to the log/flange assembly. this last step warped it which required machining to get flat again. Had I welded the assembly to the flange last, I'm sure it would not have warped. Live and learn. The car has been running beautifully and has not developed any cracks yet. Time will tell of it's reliability. BTW, turbo is a GT2580RS running 14psi on stock internals. I'll post some pics of the finished product soon.
Reply:I know that I'm a little late with this, but are you sure you're welding the tubes to the correct side of the correct flange?To me, it looks like the top flange in the first picture would mount to the block (oval ports), while the lower flange (with the oval ports on the top side machined to round on the lower side) should be turned over so the oval side mounts to the first flange while the pipe should be mounted to the 'rounder' side of this flange.I may be incorrect in this, but it does make some sense to me.Lane
Reply:i called the flange seller and he said they did it that way for penetration reasons. I ended up porting them anyway.
Reply:be kind, it's my first one! one fuse pass, one top pass with filler.