When my 68 Roadrunner had a 451 in it with iron 452 castings with big valves and a pocket port, it went 12.20's at 112. The next weekend I swapped on a set of out of the box Edelbrock RPM's. The following weekend i went back to the track and it went 11.70's at 116. The only thing I changed was the heads. The weather conditions were almost identical. I know the performance may not be all that, but at the time this car was my daily driver.