Euro distributor vs California gas ?

[Stanley]

Spent a good bit of time over the last 48 hours reading posts on the topic, studying my Nissan 72 L20A & L24 series engine manual. Not feeling any smarter, though. Got '73 240Z with SU's, C211 head & cam, nearly new euro non-emission distributor. Had to retard the timing a little to stop ping when they put the new head a couple years ago. Maybe a little more compression.

Recently read (no controversy) that initial advance is 17 degrees at 700 rpm for the automatic, also that it makes 15 deg. centrifugal. Not going to happen on CA gas.

Putting all the numbers and technical stuff (like the esoteric diagrams on page EE-31) aside for a while, I figure there's two ways to go. Either keep the vac advance and set the initial as high as I can without ping (probably about 7 deg at 700 rpm, have to test), or else cap the vacuum and set initial at 17 degrees or so (17+15=32, maybe about right for 91 octane gas).

Obviously I'll need to do some road tests but someone with experience might have some ideas? Car is a more or less stock daily driver but I'd like to run the quarter a few tenths of a second faster next time.

[Stanley]

Found this on the site:http://www.classiczcars.com/forums/engine-drivetrain-s30/23991-bypassing-vacuum-advance.html

The posts by J L Purcell and Carl Beck answered my question about as well as possible.

Finally figured out (when I added the numbers and divided by 2) that the double curves on the vac and mech advance graphs in the manual represent allowable values for testing the distributors. It was confusing since none of the numbers coincided with the numbers on the spec sheet. Also, the manual seems to switch between degrees at the distributor and degrees at the crank whenever they feel like it.

Anyway, checked it last night, my timing is (dare I say) too retarded at 22 degrees total, maybe I didn't tighten the bolt enough last time I set it. So I'll advance it a little today to get it closer to right, and do some testing on the hill, and with the stopwatch, later next week.