[Caprimaniac]

Very good suggestions & tip.
Have not thought of the bearings. Will check to see what they're like. (I remember seeing my IDF's double- sealed bearings, but not the DCNF's. They have passed into the shadow of the V8 fun...)

And on the distributor diaphragm; yes- I agree. As a matter of fact my old man told me that some were supposed to have a hole on the rear side, so no vacum is present on the return- side of the diaphragm.
Gary; on the dual diapragm (Iguess this is the type they use on turbo engines?)- should I route manifold vacuum to both sides of the diaphragm? wouldn't they even out each other?

I have gotten further tuning the carbs: The middle carb need the idle screws 1 1/2 turn out, whereas the front and rear make it with only 1/2 turn out. Since all 3 were 11/2 turns out- soot and unburnt fuel may have made some of the cylinders come on and off? Could explain the popping exhaust as well. - Unburned fuel igniting in the exhaust.

But then I'm curious... Why is the middle carb only sensitive to the idle screws beeing moved inwards? Some blocked fuel passage? Bad filter? Wrong float height? Bad vacum/ leaking inlet gasket? Time will tell, I guess.