Deceleration Valve

This valve is used to prevent backfiring in the exhaust system during deceleration. The valve is normally closed, but it opens when manifold vacuum increases during deceleration.

The increasing vacuum overcomes the spring pressure, allowing additional air into the intake manifold to prevent an overly rich mixture from entering the combustion chambers. Air trapped in the chamber above the vacuum diaphragm will bleed, at a calibrated rate, through the delay valve portion of integral check and delay valve.

This reducing vacuum acts on the diaphragm. When the vacuum load on the diaphragm matches the spring load, valve assembly closes. This shuts off air to the intake manifold.