Hello Al,
First of all, you can't "seal" a rotating shaft running thru a hot manifold without extreme measures. It will always be under pressure and will always leak some. You can make the "fit" tighter somewhat. If you think it is worth the effort, you take off the manifold to the bench and search websites like McMaster-Carr to find a bushing to use or modify. Then try to redrill/line drill the manifold casting so as to press in the new bushing(s)...provided riser shaft is not worn in to several diameters..... and provided you don't run into broken block studs/bolts and etc.
Or you can buy a good used manifold with tight heat riser, no cracks and no broken ears....
Or you can forget about it and work on something else.
Click
