[Adger Smith]

Rob,
That is good info from your engine guy. I was headed that way. He has increased the cyl pressure. You might need to close up the plug gap a little if you are running it pretty wide. I have found that big cu in engines with 18 deg heads don't like a lot of timing. The plug is located in the chamber high and close to centered. It doesn't need a lot of timing to get the flame front over the dome and get pressure rise. I would also use a non extended tip plug with alky and that head. The wet alky /air mixture hitting the hot exposed extended tip could ignite before the spark.
Good luck with the tune up.