Where is vacume source for exhaust heat valve?

[ScottH]

Not sure if the term "heat valve" is correct but it is the part that is part of the exhaust manifold that closes during warm up and opens after (heat riser?). On the 84 305 I recently picked up there is no vacume line attached.

Also can anyone tell me without a vacume line does it stay in the open or closed position?

Any info is appreciated.

Thanks.

Scott