Re: 1954 Packard Pacific Oil pressure sending unit 4 way brass tee adapter/ Auburn style dash panel

Posted by Ross On 2019/11/12 20:10:45

Here is a quick test of a vac advance. Leave it hooked up and attach a timing light in the usual manner. Find your mark while the engine is idling and then rev the engine up to 2500 or so. You will see the timing mark march quite far up and away from the pointer. Now snap the throttle shut. If the vac advance has been working properly the mark will drop back a good distance instantly, and then fall back the rest of the way as the revs drop. If it just leisurely walks back as the revs drop then the advance was not helping.