This would be on a stage 2 4.1 274 cu in motor with gn-1 heads-224/224 roller cam. i figured it to be about .625 using 1.55 as a reference point or .675 using 1.50 ratio as a reference point. this cam is a custom grind that had already been in a street driven 6109 block but was too much for the 3.8.