Spark Advance Tuning/Questions

I'm trying to do some work with the spark advance for my 383 w/ 16197427. When Idle Spark is active, I can watch the advance fluctuate randomly between 19 and 27 degrees. When I disable idle spark (increase min temperature to max value), it stops fluctuating. Is there anything wrong with disabling Idle Spark permanently and just running off of the Open Throttle spark table? I have identical values in both tables anyway.

Also, I have been searching but I haven't been able to find some guidelines for tuning the spark advance. I started with the SA table from the chip that came with the crate engine. As I have been driving and tuning the VE tables, I have seen knock retard here and there in the datalogs. Do I just reduce SA in those areas where knock retard is happening until it goes away? In areas with no knock retard, is it viable to increase SA until knock retard is seen, then back it off? How do you guys go about tuning SA?

Driving home from work today, something gave out and the engine just quit. It would crank but I couldn't get it to fire again. I look down into the throttle bores and they look dry, like the injectors aren't firing. I'm suspecting the pickup coil or distributor as they are original from 1990. The rest of the ignition system is a year or so old because I was chasing a really rough idle problem until I figured out it was a bad ICM.

Finally had some time to work on the old beast. New distributor came with a new ICM, pickup coil, cap, and rotor. After installing and resetting the base timing to 0 degrees she's purring again. So same question applies... How do I go about tuning spark advance?

spark advance is voodoo for sure

you're trying to burn all the fuel. thats all

basically if you don't have enough advance, you will be down on torque and vacuum.

as you increase it, itll eventually reach peak vacuum and power, and run smoothly

then itll plateau for a few degrees

then itll start losing vacuum and power

then itll ping.. then knock.. then melt a hole in a piston

ideal spark advance varies with temperature, fuel grade, compression, combustion chamber design

experimentation yeilds best results

Thanks for the tips. Is there a way to use the data logs as an indicator of when it's safe to increase SA and when to back off? I know there is the knock count and knock retard history table with history average that can give an indication of what's going on. Can the MAP sensor reading also be an indicator of the amount of vacuum?

I experimented with the timing during a long drive tonight. I ended up adding 5 degrees to the entire table. The drive included low and high speeds, and some pretty steep grades. There was some knock retard here and there, but for the most part it seemed to be beneficial. I've attached the log and current bin.