Re: {Chrysler 300} Engine timing with a Vacuum Gauge

One thing that I learned early on while in the fuel systems lab in Chrysler's Highland Park engineering center is that pretty much every engineering decision made on a vehicle is based on a large set of considerations at hand and results in most final decisions being compromises of various factors to achieve the best overall running vehicle under a range of operating conditions.

This includes basic engine timing settings. Achieving the optimum engine idle timing setting for your engine alone does not necessarily account for all the other considerations that an engineer uses in making their final judgments in the spark curves.

Using the manufacturer specified setting for idle spark is the best approach to use, not the setting that is optimum alone for your engine operating only at idle

Steve

On Tue, Jan 4, 2022 at 7:53 AM william ELDER <belder@xxxxxxxxx> wrote:

Even on a brand new engine, every component has minimum and maximum tolerances while being machined. So every engine will have its own identity. Engine timing was created by the manufacturers as a ball park setting. If your engine is in good running condition you can obtain that engine’s optimal timing setting with a vacuum gauge. Warm the engine up and set the engine idle speed to the proper setting. Connect a vacuum gauge to a manifold vacuum port. Do not use a carburetor vacuum port unless it originates below the throttle plates. Start to advance the distributor. Be careful as you advance the distributor engine idle speed will pick up, reset it to the specified engine idle RPM. What you don’t want is for the distributor mechanical or vacuum advance to kick in. Follow this procedure until you obtain the maximum vacuum reading possible. Now retard the distributor until the vacuum gauge setting drops 2”hg. That is the optimal timing setting for that engine.
You can go back and check the timing with a timing light. Most performance oriented guys will use a total engine timing, set at a high enough engine RPM. This ensures that both the mechanical and vacuum advance from the distributor has kicked in. Don’t quote me on this , but I think I heard 45 degrees at 3500 RPMs for a 440 engine. Mopar performance also sells engine vibration timing tape. It is self adhesive, but the vibration damper must be spotlessly clean and grease free. I have the Mopar stuff on my 300K and its been on there since 2017.

Hope this is Helpful
bill

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