Heat Riser Valve

Mine was rusted and jammed in my 1969 Dart slant, so I cut it out and used a bolt and serrated nut to plug each hole (separate ones, don't clamp across w/ a single bolt or you could crack the manifold). I don't think it made much difference in Atlanta. Even in the days of TBI, I don't think the heat riser was needed, nor the exhaust cross-over in the intake manifold of V-8's. Since MPFI of the mid-1990's, they definitely didn't have them.