I believe Car Craft did an article on that one last year as a BIG no no. It varies way too much. Took a '74 Dart at 3450 pound at 14.2's Put the same drive train into a '70 Duster at 2850 (roughly a delta of 600 lbs) and ran 13.0's. Or 0.2 sec per 100 pounds. See ya, Mike