I am building 1983 351 windsor engine. I just pulled a ported vacuum switch off the thermostat housing. It has 3 ports - "1", "2", and "D". What does this switch do. I have heard that it is egr related and i don't need a new one since all the emmissions had been removed. Someone else said it has something to do with a spark delay valve and the vacuum advance on the distributer. What is a spark delay valve? Do i need this switch? It's $50 bucks at the ford dealer, so i'm hoping i don't. Where can i find a vacuum routing diagram for this engine?
It run's in my mind that my '85 351w 4x4 c6 had a vac diagram on core support ,hood, or inner fender.This should answer most of your question. I've seen the thermal vac switch used both way,alsovac adv was tied to port off carb above throttle plate and even then it was orficed to regulate when adv was activated. A ford serv manuel would help. Unfortunately I don't have a way to send the picture. Good Luck Chuck Caddy 53:-)
More than likely it is the vacuum switch that controls the EGR. It will keep the EGR valve closed until the engine is warm enough to handle the recirculated gases. I lost mine a few years ago??!! You do need a vacuum source hooked to the vacuum advance on your distributor. It should run from the timed port on your carb (usually passenger side front) to the vacuum advance. If the emissions equipment has been removed, you no longer need a thermal vacuum switch.