Yella Terra U/Lite 8mm Bolt On Shaft Mount Roller Rockers, 1.7 Ratio (Pair) (YT6645-2)U LITE ROCKERS LS1 1. 7 SHAFT Suit GM LS Part Number: YT6645 2 Yella Terra has developed shaft and pedestal systems for late model engines that have less than half the nose weight of other rocker designs to correct valve float when some performance camshafts are used with lightweight valve train components and conical springs. The result is greater RPM potential without sacrificing strength or reliability. Standard and high ratio options are available.