in the six pack tuning post it referred to the ports in the venturis. with the engine running use your finger and block off one of the ports and see if the engine picks up rpm or drops rpm, then block the other port and check for the same rpm condition. at this time I don't recall if a increase in rpm meant rich or lean or if a drop in rpm meant rich or lean. also firecore makes a great distributor that is very easy to adj the total. my 383 really likes a lot of timing 48 to 50 total. hope this helps. if you can't find the tuning post let me know and I will try to get it to you.