The previous 150/340-pound (closed/open) single valvesprings aren’t stiff enough to manage the extra mass of the Crane solid rollers. They would have gone into damaging valve float by 5,000 rpm. Wood installed Crane-specified double valvesprings with surge dampers that are stable to 7,400 rpm. They’re matched with Crane chromoly retainers and single-groove locks and provide 190 pounds closed and 425 at 0.555 lift. Installed height is 1.830 inches.