Classic/Antique Car Repair: 1954 corvette spark plugs keep foulin out with black carbon build up on plugs, ac delco, vacuum advance

Question
1954 235 auto 3 one barrel carbs side drafts engine and carbs rebuilt was fine for two weeks now.Its keeps fouling the plugs out with black carbon all i do is wire brush the plugs off and it starts right up,I'm using unleaded fuel is that ok ? What about the plugs ac delco R45.I noticed that the vacuum advance is a metal tube that is attached to the intake manifold the advance module underneath the distributor feels like its rubbing something inside where the metal is attached  

Answer
WOW a 54 cool

Ok first off Unleaded=big no Unless the head was rebuilt using hardend seats, if OEM use lead additive.

2nd I do think the problem IS in your vacuum advance,  

Without the vacuum advance the distributor can only vary spark timing in proportion to speed and ignores its need for approximately 20 additional degrees of spark timing ("advance") at light loads: (idle and cruise conditions)
So it seems to be carboning up because its running retarded like me sometimes.

I'M not sure whats rubbing, that you'll have to troubleshoot.


As far as plugs are concerned I would use NGK B6Y @.035 gap

Ac Delco are prolly made in china now

Let me know if this helps

Mike