Buying intake manifold gaskets for a 400, What do I need?

[WH23G3G]

I still get puzzled about buying the intake manifold gasket for the 400. I've got the Valley Pan tray. I need to get the rail gaskets. But I've seen cork gaskets that go in place of the Valley Pan. Am I suppose to use both? I've heard of people blocking off the crossover. What do they mean?

[The70RT]

I never used cork end gaskets. Just sealer. Blocking the crossover means the center exhaust hole in the middle.

[375instroke]

Rail gaskets?  The pan is the rail gasket.  A small bead of silicone in the corners is all you need, as long as it's clean.  This is what I use everywhere else:



I've traded intakes with a friend before, and reused the gaskets and neither of us had leaks.If you want to block off the crossover, which prevents hot exhaust from heating up the intake, you can cram a bunch of aluminum foil in the passage.

[Nacho-RT74]

no need for any extra gasket beside the valley pan EXCEPT if you have milled down the intake and heads and you are getting back stock heads height with same intake manifold.

Block the crossover will mean block the center holes to stop the exhaust fumes from passing below the carb to heat the gas mix and choke coil. That is used to street cars but affects somehow performance being gas is constantly getting heat. Will sacrifice the manifold choke coil if you use it, unless electrical assisted, what in that case will make open slowly than with both systems working.

Is also linked with the EGR valve what will be the major "sacrifice" if you have hooked the EGR system.

There are valley pans with crossover ducts access already blocked, so if you want, with those won't need any extra piece to block it.