Hy 49dream, Chevy exhaust manifolds which have their "log" below the exhaust ports, tend to "shrink" or curl in on the ends when they are removed. Because of this problem, a lot of the later ones were cast with a connecter bar across the top. There are turnbuckle type pushing tools available, to stretch the manifold back into shape, I would heat it up ib the oven before I tried to stretch it a 1/4" though. I dont remove those manifolds anymore without having those tools in place to hold the manifold, so it can't shrink, hope that helps