The controlled combustion system used on the 8-350 engines limits the hydrocarbons and carbon monoxide emissions from the exhaust. The system includes an engine designed for low emissions, lean carburetor calibration at idle and part-throttle, plus lean choke calibration.
The engine has ported spark advance, with the vacuum take-off just above the throttle valve so that there is no vacuum advance at closed throttle, but vacuum advance begins as soon as the throttle is opened slightly. To reduce emissions at idle and at lower engine speeds, the engine timing is such that the distributor will not have centrifugal advance until about 850 rpm.
The lean carburetion is possible because of the heated air system (thermostatically controlled air cleaner). With the heated air system operating, inlet air temperature is around 115ºF after the first few minutes of operation. This makes the use of lean carburetor calibration possible and the engine still responds well in cold weather.