Hi again.
I must admit to not knowing too much about advance curves until yesterday. Now, I've done a lot of reading, and I'm wondering if the 123 electronic ignition is what I should have (cost aside for the moment -$500). Clearly, they come highly-recommended everywhere I read about them. But....according to their spec, the curves are pre-set, so you can't monkey with them(?) I have a B20 E - which has the lowest advance for all B20's at high RPM (32 degrees, due to larger exhaust valves I assume), which I believe it reaches at 3800 rpm. This, they say is the factory setting, which will be pretty conservative, and if-so, then with more or less performance mods that may not be the right curve for mine, or anybody-else who has modified the engine. All other settings offer more advance, not less:
http://www.123ignition.nl/pdf/123B18B20.pdf. right at the bottom of the file.
To see what I mean, I found a great website which lists all of the factors affecting timing:
http://www.jcna.com/library/tech/tech0013.html just scroll down a tad. According to that, with the head ported and shaved, and a (John Parker) header, all three of these call for less advance than what is factory (although, premium gas would move the timing the other way). I guess the question is: how-much difference would it make??? Also, I assume there is no vacuum-advance, which I 'know' is somewhat less important, but still...?
I'm thinking I'd like to stick with a 'real' distributor, get some sensors instead of points, and see what happens with the mechanical advance below 32 - I suppose the only way to know for sure what is right would be to get on a dyno, but for now, I don't think I want a 123 which cannot be altered.
What's the deal with a day at the dyno - what does it cost, and how valuable would it be?
???