1. Any carb vacuum fitting not connected should be capped. 2. The heat riser valve can be checked by moving it when the engine is cold. The arm with the counter weight should move easily up and down by hand. Check to see that it moves to the open position when the engine is warm. 3. Start by blocking off ALL vacuum taps from the manifold - carb, vacuum gauge, power brakes, distributor. Then check the manifold-to-head seal. Manifold-to-head vacuum leaks can be checked by putting various petroleum-based compounds at the juncture. Propane from a hand-held (but unlit!) torch will cause the rpms to increase. Kerosene will cause the rpm to decrease and a whitish smoke. Motor oil from a lube can will cause a decrease in rpm and blue smoke. Basically, any of these temporarily replaces the air being pulled into the manifold. If there is no rpm change, watch the rpm as each of the above vacuum lines is reconnected. There should be no change. If there is, the hose or the component is leaking. jack Vines July 2003 =================