(1) set initial with "vacuum gauge method" (2) that's a SB dist so weld/file slots to get 35 total (initial above plus slot length (mechanical) advance (31 if mag heads) (3) toss the heavy spring with elongated loop on one end & sub in a mr gasket or MP light spring (keep the other OE light spring in there) & mix/match springs till you are just under the pinging point at WOT up thru the gears on your hottest/driest (most likely to ping) day and you want the curve to start no less than 200 RPM above your hot in gear idle speed.(4) Then plug in/adj the vac can staying just under the pinging point in everyday driving under varying load (in hg) conditions on your hottest/driest (most likely to ping) day and CCW with a 3/32" allen wrench slows the curve (not the total). On #2 File the welded slots slightly less than the chart as it reportedly is a bit off & you will be in and out of the dist several times (at least) till you get it spot on but it is worth it & you dont want to have to make a return trip to your welder.