Before shutting down I ran about 20 minutes with Seafoam in the gas. If that matters.

About 4000 miles since last valve adjustment. Car running great. #1,3,4 are nice gray and #2 has white soot on the stem

Is this just a leaking valve due to mileage since last valve adjustment or ???

Lean cylinder or it got most of the additives that were in the fuel.

After the valves and timing I'll check the carbs. Had no popping through the carbs but ill resink to be sure its not tunning lean.

Should I spray the white stuff down with carb cleaner before putting on the exhaust or just leave it alone?

Never used sea foam before. It smelled like straight alcohol. Thanks

Just clean it off as best you can. Should be a white powder. Shouldn't be a problem though.