The most common failure is caused by the metal tab on the rotor arcing to the carbon post in the cap center. This info is all on MSD web site and professionally described but here goes. Bend the rotor tab toward the carbon post so it touches the caps post (not crazy pressure but for sure touching). If not touching an arc eats the post away every time it discharges the coil.
The second known problem is the rotor timing. The issues is the location of the rotors (conductor ?) or tab that aligns with each cylinders spark plug contact as it rotates to deliver each spark pulse through the cap. This one angers me a bit because if it is off or bad the distributor was built poorly and there is no home repair. buy some POS adapter to fix their mistake? See tech paper here
http://www.msdignition.com/uploadedF...or_phasing.pdf