variable duration lifters (rhoads)

67Cuda, how large is your engine? With 228* @ .050, I don't think I would bother with them, (340/360). The biggest problem I see with using them is some builders will install these AND use a hi-volume oil pump. Since they work off oil pressure and time, as RPM increases, oil pressure increases, time decreases, they can't bleed down so you have (in theory) full lift/duration at RPM. Hi-volume pumps reduce their performance. Don't use them together. JMHO. 67Cuda, 228* @ .050 and .512, sounds like a good grind, with fast rate of lift. Terry.