Manifold Heat Control

Most engines have automatically operated heat controls which use the exhaust gases of the engine to heat the incoming fuel-air charge during starting and warm-up. This improves vaporization and mixture distribution. When the engine is cold, all of the exhaust gas is deflected to and around the intake manifold "hot spot". As the engine warms up, the thermostatic spring is heated and loses tension. This allows the counterweight to change the position of the heat control valve gradually so that, at higher driving speeds with a thoroughly warmed engine, the exhaust gases are passed directly to the exhaust pipe and muffler. In the ram induction system, there is a heat control chamber in each manifold to operate the automatic choke and to heat the fuel mixture after warm-up. A heat control valve in each exhaust manifold will by-pass the exhaust gas through an elbow to the intake manifold heat control chamber. Heat outlet pipes then carry the gas down to the "Y" connector under the heat control valve. Heat control is regulated by a coiled thermostatic spring mounted on the exhaust manifold. A counterweight is mounted on the other end of the heat control valve shaft and this counterweight, in conjunction with the thermostatic spring, operates to close and open the heat control valve.