This is very dodgy situation at best. The boss's that are part of the cylinder head that the bolts thread into are open on the bottom to the valley area, directly above the lifters. The shavings will end up there and ultimately your
oil pump (not good). You can do this without removing the heads but you will need to remove the manifold to do it properly. Once removed you will be able to put a rag under the area to be repaired.