My ignition timing is going crazy, very unstable

You may have a broken or weak spring that retracts the weights of governor controlling mechanical advance. Also sticking governor weights will cause fluttering timing at idle.

After 30 years or so, some of the parts on our cars become crusted from dried lubricant, and corroded from just being around. The distributor’s governor is exposed to the elements and often regular maintenance as well.

Disassemble top side of distributor to examine governor springs, clean and lubricate the action of its weights. Slant six distributors require a few drops of light oil be placed on the felt located in distributor shaft under rotor button at every tune up 12 months, or 12,000 miles. This oil point lubricates the innards of the distributor.

To remove top plate of distributor, look under oiling felt for a horse shoe shaped wire retainer that acts as a spring clip holding governor on the shaft. Sometimes it comes out easily, and sometimes it is a royal PIA to extract, but once it is removed the plate covering the weights comes out easily.

Pay attention to direction of slotted weight retainer as the rotor button attaches to this part, mark it if needed, if this part is reassembled 180 degrees from its original position, the timing will be out 180 degrees when distributor is reinstalled in its original position, and engine won’t run.