Checking the operation of the hot-spot valve 

Guide to checking the operation of the hot-spot valve between inlet and exhaust manifold on older cars.

Some older car may have a hot-spot valve these cars with a combined inlet exhaust manifold have a thermostatically controlled hot-spot valve to assist vaporisation in the exhaust manifold, just below the point where the two manifolds join.
It can be identified by the short shaft that protrudes from the side of the exhaust manifold, and is linked to a stop by a coil spring.

Check that the shaft is free to turn. If not, disconnect Spring the spring from its anchor point and free it from the slot if the valve shaft will not soak it
penetrating oil and rotate it backwards and forwards until it is free.

Reconnect the spring. Twist the shaft and make sure it returns under spring tension. If the spring has lost its tension, buy and fit a new one.