Re: Blue print 347 ford stroker fouls plugs
I'm thinking that you may not have your timing marks indexed correctly. I say this because when you advance the timing, your manifold vacuum goes right up to where it should be. Does the engine ping under load when you advance the timing?
Ford used at least three different combinations of vibration dampers, timing pointers and front covers on the small block Windsors. If you mix them up, it's possible to be off on your tdc mark.
I would try bumping your initial timing 2 degrees at a time until you get a slight pinging under load, then back it off 2 degrees. This may solve your problem.
1966 Falcon, 347 stroker and C-4