Vacuum Delay Valve

Remove plug from intake manifold. Disconnect spark delay valve-to-distributor vacuum hose at distributor and connect directly to intake manifold vacuum.
On California models, disconnect water thermo valve-to-spark delay valve vacuum hose at spark delay valve and connect a vacuum gauge. On high altitude models, disconnect spark delay valve-to-carburetor vacuum hose and connect vacuum gauge.
Start engine and record vacuum at idle. Pull intake manifold vacuum source off and record time it takes vacuum to decrease 11.8 in. Hg from idle vacuum reading. If time exceeds 4-6 seconds, replace spark delay valve.