just finished rebuilding my 455 for 67 bird now i have run into a problem we put the 6x heads on the 455 and the gaskets dont cover a port in the middle of the head above the normal port. so for some reason there seems to be an extra port. what this port does is beond me does not seem to go any where. stuck a wire down it and blew air into it to find out where it goes with no luck.. Any ideas?

Just a dead hole. Some people think it's for cooling.You don't need to cover it.

thanks jim just called machine shop they said same thing.still find it strange. should i fill them with jb weld?

I have the same in my 6X heads on my 455, no need to fill them on mine, the gaskets cover just enough so it's not noticeable, but on many of the 6x heads anyway, this port is indeed a dead end. You should be just fine. Many heads it's set up for a heat cross over to help with warm up...

Brett! - 67 Drop Top 455!

The purpose of the "port" is to isolate the exhaust crossover passage from the top side of the head. Pontiac engineering found an oil temperature reduction with the newer design. Don't fill it in. Just use the right intake manifold and gasket.
DJ

If you don't seal it with the proper gasket or fill it in, if your engine is ever exposed to rain or washing the hole will fill with water, which will boil out quickly when you start the engine. It's a little odd, but does no harm other than leave ugly residue.