Mystery 318 wants 30* initial timing?? Pinging hard

I have blasted carbon by trickling water down the carb. That works also as long as you just trickle it and not pour. Carbon blaster chemicals are also sold. What port is the vacuum advance hooked to? Un plug it at the distributor and plug the hose with a screw or golf tee when checking timing. It should be connected to a port higher up on the carb just above the throttle plates for a stock engine.