i just recently rebuilt my 305 in my 84 chevy truck and i used the same plugs temperarily. well i had been having this problem with it smoking out the valve covers. so i decided that i was going to put new valves and lifters in it and that still didnt solve the problem. So the only thing that i didnt change was the spark plugs and what did i know it solved all my problems. Now i am trying to figure out what i need to do to raise my truck 2 inches in the rear and 4 inches in the front.