Joe, As I understand it, there were no exhaust manifold gaskets on Nailhead. The surfaces were milled perfectly flat and true at the factory and assembled without gaskets. Also, the Chassis service manuals make no mention of gaskets for reassembly of the exhaust manifolds, but they do discuss reinstalling the exhaust bolt retainers after torqueing the bolts to 10-15 pounds. After saying all of that, I have never seen a Nailhead without exhaust gaskets. I think they all warped over time with age and heat cycles leading to leaks. Most shops and owners corrected that with gaskets. None of the engines with gaskets I have pulled apart or seen in junkyards had any cracks in the manifolds. I would suggest that cracks are more likely in manifolds with leaks that are left unaddressed by gaskets.
