my 455 when reaching 180 from idle starts gradually revving up to 2500 point unsafe at stop lights I swapped carbs from other good running cars I have its a 2000 mile rebuilt 455 it has good compression check but vac guage test shows a very low 10 lb 15lbs at idle could my valve springs be bad causing revvup? it has no vac leaks at all I am puzzled last cars I seen this do was valves or springs