I haven't had a pertronix ignition system but I have had a lot of trouble
with B20s overheating on prolonged idling. I think it is because the fan
doesn't move enough air through the radiator, and maybe a bigger radiator would
also help. To the best of my knowledge there are not any systems in common
use for the B20 that adjust the timing other than the ones that have vacuum
retard and the standard vacuum and centrifugal advance mechanisms.
Having said that, if there is a vacuum retard you might want to disconnect it
and also check your ignition timing. Not being advanced far enough will cause
it to run hot, especially under power. That will also make your exhaust run
very hot - so look for a glowing manifold when this happens.
I set mine at about 20° BTDC at idle with vacuum advance (if present) still
connected. The vac advance is good for about 10° so that compensates for it,
and eliminates the need to disconnect it, adjust for the differing idle speed,
and then readjusting back when you hook it up again.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma