obd2 exh manifolds warped?

[static]

Just got back from machine shop after getting them to machine obd2 manifolds after welding up the EGR ports.

according to the really old school (and really old too) machinist, the flange was warped pretty bad.

is this typical with used obd2 manifolds? i understand the SS flanges on those are not the best for not warping (i.e cast iron is supposed to be much better)
And how perfectly flat do they have to be to seal enough to not leak in long term?

[hoveringuy]

I just got done welding mine up and they weren't warped at all. It was a PITA to pull the broken studs out of the other end, but the manifold was straight. I flat-filed them after welding. There were a few high and low spots but nothing that would have kept them from sealing.

[static]

thanks

btw, the f-ed up bolts that are on the other end is my next project. What's the best way to get rid of them so i can just use regular bolts instead?

[etxxz]

^^ yes, but there's no need for it, just buy new hardware if they are badly rusted, use high temp spray pain to protect them if anything...i personally would use normal bolts, that would make everything so much easier.

as for the manifolds, when you weld the metal it heats up unevenly, if it cools too fast or in a bad manner to be very vague it can warp. ever weld aluminum? you're problem was not the used headers, it was the welding.

[static]

sh!t

the guy who welded the manifolds put them in a sink with cold water right after - i guess that did it

but surprisingly enough the old machinist said that it wasn't that, but that it was engine heat + perhaps uneven torque on teh nuts that warped it.

yes, so do i remove the OE bolts from the downpipe side? drill them out?

[FredK]

Who the fock drops a hot weld into cold water? That's a recipe for freezing in a whole bunch of screwed up stresses and warping shit.

Anyway, the OBD-II bolts are actually press fit studs. The best way to remove them is to heat the hell out of the stud with a torch and pound it out with a sledge. Or use a shop press.

[hoveringuy]

Don't try heating unless you have Oxy/acetylene. Anything short of that willl just annoy it. I tried MAP gas and it didn't do a thing.

A shop press would probably work, even without heat.

I got them out by cutting them flush and drilling. I also flat-filed the two joint flanges because they weren't very flat.

[PiercedE30]

sh!t

the guy who welded the manifolds put them in a sink with cold water right after - i guess that did it

but surprisingly enough the old machinist said that it wasn't that, but that it was engine heat + perhaps uneven torque on teh nuts that warped it.

yes, so do i remove the OE bolts from the downpipe side? drill them out?

WTF?! Dunking a recently made, hot weld in water will absolutely cause it to crack and break. That guy is a moron.

[hoveringuy]

It's old school farm welding... it was common practice to quench welded pieced to temper them.

[matt]

It's old school farm welding... it was common practice to quench welded pieced to temper them.

Around here its more common to do things the right way...

I can usually get the studs out the other end with a hammer. Don't order the replacements from BMW... it's a regular bolt that costs ~$20 and is more likely to break than the original studs.

[PiercedE30]

Usually when you quench something, you use old oil.

[static]

It's old school farm welding... it was common practice to quench welded pieced to temper them.

crap, that's what the old machinist said - will make it harder.
in any case, prior to putting it in sink, it wasn't extremely hot or anything, i touched it with finger and it burned me somewhat not melted my finger. (You can tell i haven't much experience with welding, but this was a learning experience )

i've used a straight edge to see how much warpage there still is and from the looks i'd say 1/2mm lift at the most on one corner of the flange - would stock gasket + pressure on flunge nuts take care of that or should i go pay to machine it further?