Head gaskets are done in the car, but GM is famous for making cars that go together quickly on the assembly line. There's little thought toward future service. That is especially true if you have a V-6 engine.
You'll want to take the head to an engine machine shop to have it checked for flatness and cracks. Cracks are pretty rare but if the head is warped it will need to be machined. On engines with the camshaft in the head, those warped heads have to be heated and straightened. Machining the sealing surface will leave the camshaft journals out of alignment. It's less expensive in that case to just buy a remanufactured head.
Tuesday, October 8th, 2013 AT 10:27 AM