portapower and a big hammer, i dont like heating frames, put the portapower in front of the bend, put pressure there and hit with the hammer at the bend, there is usually a slight kink at the bend thats where you want to hit, if you can back up the hammer with a big piece of iron, like using a dolly on body work, a little clarifacion on my post, if frame is bent in toward the other side use the portapower, if bent up or down use a jack and chain to hold frame in place while straighting