Whilst playing with springs and weights is one way to go about things (a most troublesome and unscientific way IMHO), another way is to get a 123ignitions distributor.
There basically 3 models to choose from:
- basic model with 16 pre-set advance curves to choose from;
- the USB programmable version. You need a PC to program the advance curve you want. This model has the added benefit of having a second curve available which can be implemented via a switch in the car. One application for this second curve is to use it for the “racing curve” or, if you are driving the car in very mountainous areas, to use it for switching between low altitude (less advance) and high altitude (more advance) curves ;
- Top of the range is the Bluetooth programmable version which you can program with your IOS or Android app. I installed one of these into a 4.2 S1 and I was astounded with the results. At one point I had the engine so responsive, it could only work as a race car. I found myself LITERALLY having to detune my own curve to make the car more road drive-able. I did post on this topic: 123 posting
I also helped a friend install the USB version into his '84 Rolls and it has transformed the car.
Obviously, the BT version is my recommendation but it also is the most expensive. No connections etc.