Car is a 68 Charger, 383, low miles since rebuild (two or three thousand) 10 years ago, stock cam, stock Eddy heads, MP duel plane, stock exhaust manifolds, MP electronic ignition with orange box and Holley Street Avenger Carb. Timing is about 34 total at about 2500 RPM

Car has been in storage for last four years and I am bringing it out. Pulled fuel tank, cleaned all lines, etc. Pulled the plugs yesterday and they were extremely carbon fouled. Plugs are Champion RC12YC and gapped at .035.

This car always had an off idle stumble and when driving straight and level it would surge. Other than that the car ran very well.

I bought the carb new and this is the first time it has been apart. Jets were 66 primary and 69 secondary. Power valve is 6.5, and squitter is 35. The mixture screws were almost exactly ½ out on both sides.

My plan was to increase jet size and to try to resolve the surging issue but looking at the plugs it seems the car jets may be to large; I would think 66 and 69 would be a little lean for this engine.

Looking for some advise on what the correct jet size should be and correct power valve should be for this particular application. Why are these plugs so bad?