The EGR system was designed to reduce NOx emissions by adding exhaust gas to the intake fuel charge via the EGR valve. The EGR valve was controlled by the carb's EGR vacuum port when the throttle is opened, which is different from the distributor's vacuum advance port. Sometimes, the EGR was controlled wia a thermal vacuum valve which inhibits the EGR valve from opening when the engine is cold. The addition of exhaust, via the EGR system, to the intake fuel charge to reduce the combustion chamber temperature to below 1600° F, which limits the formation of NOx or Oxides of Nitrogen. Best thing to do is do away the EGR system....the engine will run better without it. Just my opinion of course.
BOB RENTON
