I was fiddling with the timing on my '83 CFI the other day. The factory setting is 6* BTDC. I found though, that the more I advanced it, the smoother the engine ran. The tab only goes to 12*, but if I go even further, it seems to run even better. Let's call it about 17*. I feel uncomfortable leaving it advanced that much, but it sure runs better, smoother and sounds better. What do we think?

well, i can only speak about this in general because i have unfortunately never got a chance to work on or let alone drive one of these CFIs.. but here you go:

with the factory setup your engine would probably like something in the 15-20° range of total Spark Advance @idle, but the thing is that the initial timing you are setting is the baseline for spark advance (at least if you disconnected the ESC or EST connector).

the ecu or spark control is expecting 6° initial timing and goes from there to add another 10-15° to that, depending on various parameters, to get a total of the mentioned 15-20° SA or whatever is appropriate for e.g. warm idle operation.

could be that your spark control isn't working that good and that's why your changes actually made a difference in your smoothness and performance that big?
also, did you disconnect that connector when setting the timing?

as said, dunno how much of that really applies to cfi, just trying to give some concepts to think about.

hth
ownor

Yes, I disconnected the EST.

does it start up quicker with the different base timing? do you feel a flat level of power as it rev's under load?

So far, there seem to no issues as it revs, just more smoothness and better exhaust note.

Start up? Maybe it starts abit quicker, but if I didn't own the car, it wouldn't be enough for me to tell.

Sounds like the car enjoys the advance. What type of plugs are you using? Have you pulled them to see color?

No I haven't. Probably a good idea. But I'm wondering what combination of things, make the car happier with at least 10 more degress of advance, than the factory specs.