The heat riser should be spring loaded. Its a heat sensing spring that relaxes as it heats up. During a cold start, the heat riser valve would be closed, this deflects exhaust gases up under and around the intake manifold to aid in warm up. As the engine begins to warm, the spring starts unwinding thus shutting the heat valve so the exhaust gases now pass directly out the exhaust manifold.
You should not hear any difference when the valve is operating correctly. What you may have is a leaking gasket or improperly tightened gasket between the two manifolds.
As Don as has stated, you need locating rings on the intake to locate the ports to the head. You should also have a gasket in there as well. You should snug the bolts to the head before tightening the bolts holding the intake to the exhaust. Once you have everything snugged up, then pull the manifolds together and finish tightening the bolts to the head.
It rarely works tightening the manifolds together then installing them.
Joe
