Hey buddy, got a question. Well maybe a couple. I was looking at the exhaust manifold and one has some really deep pitting going so was considering replacing rh side. Along with the pitting, the heat riser valve doesn't move very freely and i think the heating coil spring won't open the valve. The casting number is 9779328. Which matches to 66-68 gto and 68 firebird. But not a 70 Tempe. Wonder if it was taken originn motor. Also, how necessary is that valve??; thankt
