Updated: Jan 5, 2021
One of the most common mistakes people make on these engines. Do not run gaskets in between the manifold and head on all nailhead. Factory never ran them for a reason. This causes the manifolds to crack and rots out the mating surface from trapped condensation. Bolting the brittle manifold down over a gasket puts it under constant stress, under normal shrinking and expansion conditions. The gasket also insolates the manifold from head, causing it too cool off too fast, rather than the heat be slowly transfered into the cylinder head as it cools. the 322/264 stock manifolds are especially fragile. all produced headers for these engines are the same way, and warranty is voided if gaskets are used. so why do gaskets come in gasket sets? gaskets get used with custom flat flange headers. also, gasket manufactures make gaskets for hundreds of engines, so they are not aware, nor specialize in any perticular engine. we work with "best gasket" brand to provide the best gaskets available for these engines.. take note below of a picture showing both cracking and pitting related to gasket use. if your manifolds have excessive pitting already, you can have them surfaced and/or run a skinny bead of exhaust rated high temp silicone around the ports on the flange. as for "french locks," they really arn't needed. i leave them off unless the customer wants them. after manifold install, i'll run the engine. go over the manifold bolts one more time, and they should never loosen up again after that, without the locks.