Need some advice, please: My 312 motor is fouling spark plugs big time (I can see signs of fouling after running just 300 miles).  Here's some back ground on the motor: just professionally rebuilt: bored .060 over and running a Mummert Blue thunder intake, Edelbrock 500cfm carb, and Mummert's mild street cam.  Removed the road draft tube and machined a plate to cover the hole where the tube was mounted on the block.  Ran an aluminum tube from this plate to top of the block where I installed a PCV valve and ran a rubber hose into the base of the carb.  Heads were gone through, too--hardened seats, new seals, etc.  Is there a clue in there some where as to why my plugs are fouling so quickly (the #3 plug fouled so bad recently it completely shorted out after less than 2,000 miles).  Many thanks for all suggestions!  Ron...