Originally posted by thedawg Yeah, my HRC mani warps CONSTANTLY. I've had it milled flat so many times that it just keeps happening more and more frequently. According to RRE, this is caused by 1) Manifold flange too thin to begin with. 2) Uneven tightening/backing out of fasteners. I use GST mani studs and copper nuts, with blue loctite and it helped immensely. I think if I had been doing that from the beginning, as well as uniformly torquing down the studs, the mani would never have warped.