GM Firebird 1967-1981 Repair Guide

Manifold Heat Control Valve (Heat Riser) 1967-74 Models



This valve is located in the exhaust manifold under the carburetor on inline engines, and in either the right or left side exhaust manifold on V engines. It can be identified by looking for an external thermostatic spring and weight, and hinge pins that run through the walls of the manifold. Check the valve for free operation every 6,000 miles and, if it binds or is frozen, free it up with a solvent.