Re: Late ignition. Timing

Posted by Tobs On 2022/11/10 5:31:37

By attaching your vacuum gauge to the line going from the manifold to the vacuum pump on top of the fuel pump, you can measure manifold vacuum.
Just do a search online for diagnosis with a vacuum gauge and you will find there are ranges of vacuum defined for different engine operating conditions. Such as ~18 inches mercury at idle. 23-28 inches in overrun etc.
If idle vacuum is low it could be due to late ignition timing or a bad idle mixture adjustment. (say ~14-16 inches) I think really low vacuum at idle could be due to an intake manifold leak. (10-14 inches) A motors manual also has a nice chart on this to refer to for our type of cars.
With a vacuum gauge, a timing gun and dwell meter you should be able to get a packard tuned up properly. A hand held vac pump is also a good tool to check the health of your vacuum advance.