What a great write up PJ and photos as well! Nice work, you can see the rubber bushing on the stem in the slot, those sometimes completely wear off,...use a new one the brass ones I like.
You may want to get a rebuilt one, and change out the vac can etc. most of those pulled way too much timing for todayís gasoline.
Those springs you should save for your suspension as they look pretty stout!
A little cash and effort tuning that up will pay tremendous dividends in your cars performance. I would shim that 053 a bit, but you are correct not too tight.
Nice examples to help everyone!
Thanks for the compliments. I don't plan on rebuilding the distributor, just used it as a demo. I myself have never gone to such lengths as to either rebuild or even dial in an advance timing curve. I have learned a lot about that from you and pulled out a number of my technical books along with the internet in better understanding the value in knowing and applying it to our cars.
I can find photos, diagrams, drawings, and descriptions, but they still seem to lack in their presentation - and few are ever a Pontiac unless you get into the HEI. So using some of the questions by our members, I did my best to answer them with a practical example, my actual points-style distributor, and then point out those items fitting of the questions asked. So I too am learning as we go along with everyone else. Now I know exactly where the advance pin bushing is and goes and how it all works! LOL Makes a lot more sense when you start talking about adding more initial advance at the balancer, but now the mechanical advance in the distributor is too much
and needs to be reduced by using a larger bushing or fashioning a stop of some sort. In the same token, if I needed more mechanical advance from the distributor, I know I can swap out the bushing, remove the bushing, or file the slot a little longer - all really simple stuff once you know what to look for, how to adjust, and the parts you might need.
The rate at which the distributor's advance comes in at "X" RPM is the "advance curve" and this is controlled by either the small springs that provide the tension on the weights, or by changing out the weights (as some kits offer). So if wanting the total advance to be all in a 2,500 RPM's, or 2,800, or 3,200, etc., you can do this by selecting and trying a mixture of different spring tensions as supplied in many of the spring kits.
So your total mechanical advance is a combination of
your initial timing
down at the balancer at idle, and the addition of the distributor's advance through the weights
. If the total is too much, or not enough once you have the initial timing where your engine wants it, you then make your adjustment at the distributor by either limiting the advance of the weights or extending the advance of the weights.
Once you have the values for the initial + distributor = total mechanical advance where you want them (generally anywhere from 30-36 degrees), you can then create an advance curve by changing out the springs (or weights in some cases) that will cause your total advance to be all in by "X" RPM's.
Then the last thing to dial in is the vacuum advance which you want to match up to your engines vacuum so it operates within the vacuum range your new bigger cam may have changed (generally less vacuum than stock), and
the number of additional degrees needed to maximize the total mechanical advance at "X" RPM's +
the full vacuum advance in degrees so it does not exceed a combined advance of about 50-52 degrees when you let off the gas, or tool along on light throttle. If too much vacuum advance, then this too can be adjusted with a stop to limit the vacuum rods travel in pulling on the points plate and advancing the points (or Pertonix set-up).
This is where a dial-back timing light would really come in handy, or the use of a standard timing light and a timing tape or balancer having a fully degreed hub.
I think that should cover it so that all can understand.
Again, this is for those who have points-type distributors, or if you do a Pertronix conversion on the points, and want to know more of its operation and adjustment. They are not too complicated and do provide reliability and performance if you know how to work on them and enjoy doing so.