How common is it to have the stock exhaust manifolds warp?

I have a noticable exhaust leak, and after about 15 minutes of driving it quiets down, my dad thinks its missing, lol. but its not.

I was wondering how common the stock manifolds warp, it seems to me that its very common. how to you fix it?
Im thinking a belt sander to the #3 and #4 exhaust port surfaces to stop the teeter totering.

So this is a six cylinder?

I don't think it's a warp but a crack. Cracks are very common. 90% of the time it is the 'front' one. You would know if there was a crack in one of the manifolds because you would hear an audible ticking sound. You would especially be able to hear it if you remove the center compartment assembly against the rear bulk head and drive. You'll hear the ticking fairly loud since the front exhaust manifold is right there.

If it's something else then it must have been caused by physical damage or improper installation at some point.

I have gone through soooo many manifolds and they are all warped. I use a belt sander to plane them flat again. Usally the port closest to the Y pipe is the most warped, then the other side, the middle one is usally straight. The gaskets compress then they warp. So to answer you question, yes very common. I have made gaskets that dont compress, I will post a how to soon. BTW becarefull sanding them straight, they are not all made equal and some take so much sanding you sand throught the welds. and don't nick the ball Y-pipe flange part.

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