1971 Mark Distributor Vacuum Questions

Hi Bill –
Thanks for answering my last questions about the turn signal lever and the rim blow horn! I am busy with these problems as we speak. Now I have a new one for you, and that’s about my distributor.
I have installed a new intake manifold and carburetor (Edelbrock) in my 1971 Mark III. But now I do not know if the distributor vacuum port is timed (no vacuum at idle) or full vacuum (vacuum present at idle). I hope you can help me with this one, so I can connect the vacuum hose to the designated port at the carburetor.
Ray
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Hi Ray –
That era of Ford built engines is set up to provide no vacuum to the distributor at idle. They did however provide an override that would automatically apply full manifold vacuum to the dist. in the event of an overheated engine coolant condition. This feature consisted of a sensor mounted into the thermostat housing with an additional vacuum line to the intake manifold. When the engine is overheated the engine timing will advance to increase the engine idle and subsequently the cooling fan and water pump speeds during the overheating in order to assist with the engine cooling. Many of these are now by-passed or wrongly installed and the system is generally not considered crucial as a cooling feature but is nice to have in order to maintain authentic engine controls. The theory of operation and its plumbing can be seen in the Shop manual. Hope this helps.
Sincerely,
Bill