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Straightening the Exhaust-Flange(s)
If your pipes have removable heat shields, and you can slide the flanges off the exhaust pipe, straightening the flanges should be easy. Once you get the flanges off the pipes, if you have a large, smooth-jaw vise, you can just clamp them flat (after protecting the chrome, of course). If you don't have such a vise, you could just sandwich each flange between two thick boards, and drive a car over it. Or better yet, take your flanges to an auto body shop or muffler shop and have them flatten your flanges.
If you've been able to straighten your flanges by the above means, great; you can skip the rest of this section. If not, read on.
Now comes the hard part: getting the flanges flattened out by yourself.
The idea is, to hold the flange sides down against the header neck while applying back-pressure at the hole-ends. Note: While it would be less complicated to simply brace the flange's hole-ends while using clamps to screw down the flange sides, I dismissed this option, as the clamps would have wedged against the heat shields and thereby bent or scratched my new pipes.
To create this setup, assemble the miniature jacks (described in the Tools Needed section above) into both mounting holes of the flange, as follows:
- Thread a nut onto each of the two bolts, nearly all the way to the bolt-heads.
- Slide a flat washer onto each bolt.
- Insert a bolt through each flange hole. Tip: The bolt head goes toward the pipe's head.
- Slide another flat washer onto each bolt -- optional.
- Thread another nut onto each bolt -- optional, but recommended.
The result should look like the following photo.
Next, find a scrap of sturdy wood; a piece of 2" x 4" wall-stud will do nicely. Hold the wood flat against the pipe's head while you simultaneously secure two C-clamps to hold the pipe-head and wood together. To do this, place the C-clamp's fixed jaw at a point on the flange 90° from the flange-bolt-holes. Of course, the other clamp goes to the opposite side of the flange. The screw-jaws of the clamps are set against the back side of the wood. See photos below.
Tip: A helper can ease the frustration of getting the C-clamps snugged up tight, as there are many awkward pieces to control at once.
Once you have the board firmly clamped onto the pipe's head, tighten the C-clamps further. As you do this, be sure to alternate between both clamps -- little by little -- until the clamps are very tight. It is important that the clamps be tight. Just be sure you don't make them so tight as to bend the flange or break a clamp.
Now you're ready to straighten the flange.
Next, slip a large fender washer or other piece of thick sheet metal (roughly 1/16" or so thick) between one of your jack-bolts (in the flange holes) and the board. Then slip another washer (or whatever) likewise under the other jack-bolt.
Now, put an open-end wrench on one of the little jack bolt-heads. Then put another open-end wrench on the jack’s nut. See photo below.
Next, begin to screw the jack-nut up against the flange while holding the bolt-head from turning. Once the nut begins forcing the jack against the washer (or whatever), switch over to the other side, and do likewise.
Now, it's simply a matter of alternating between the two jacks; keep tightening the nuts, little by little. As you do this you should begin to see the flange straightening out. Note: I find it amazing how tightly the nuts must 'jacked up' to straighten the flange, compared to how little force was used to accidentally bend it. I guess that demonstrates to power of heating and cooling.