Classic/Antique Car Repair: Distributor settings, Setting timing to optimum

Question
Hi Dick, thanks for the reply about the carb., cleaner question.  New question.  Re: 1951 Packard 200 distributor.
Please explain the purpose of the calibrated plate between the upper and lower distributor bodies.  After I set the points, what is the next step to set the timing, as well as where to clamp  the upper part of the dist., to the plate.  What is the correct order of this operation?  I know you will have the info 'cause you have a '51, 200 too.  Thanks again.....Steve


Answer
Back in the days when these cars were new, gasoline was not nearly as well regulated in quality as what we have today.  Many cars had the provision you describe so that the owner could make fine adjustments in the ignition timing to compensate for problems with changing octane ratings - retarding the spark to reduce "pinging" when he got a batch of bad gas, or advancing it in cool weather and with good gas to take advantage of the better performance and economy available.

The way I set these cars up is to clamp the dial at the mid-point (it is labeled "0" degrees of advance), and just leave it there. Then I adjust the whole distributor body, plate included, to the optimum setting for the particular engine and gas used, using the following procedure:

First, you must always FIRST set the point gap (or better yet, if you have a dwell angle meter, use it to set the points so that the dwell is at 30 degrees, plus or minus 2 degrees.)  If you don't have a dwell meter, just use a feeler gauge to set the points to the recommended gap, that will be close enough that car will run fine.

Next, take the car for a ride:  Warm it up thoroughly, make sure you have the gasoline brand and grade you are going to be using, then find a place where you can drive at 30 MPH in high gear, and play with the accelerator trying to just barely induce a mild "ping" on moderate acceleration - adjust the distributor position by advancing it a little bit at a time until you hear the pinging.  When you have it set there, you have the optimum setting, so lock it down and forget it.  If you switch brands or grades of gas, or if you wind up operating the car at high temperatures and start to hear more pinging than just very mild, you can use the adjuster plate to move the timing a few degrees toward retard to clear up the pinging. The timing recommendation in the Packard shop manual may or may not be what you have chosen for a setting, but don't be concerned about that - the "timing by ear" method always produces the best result for performance and economy with today's gasoline and your engine's condition.

Dick