The crower stuffs are working great for me. I rev to 8,600 rpm's daily without ever breaking anything. Jubee, you know about my SR head it is the best around. Crower 280/280 cams with 12.5 mm step 3 lift. Crower springs and retainers. Greddy Rocker arm stoppers. HKS solid lifters and 3 days I spent shimming and adjusting valve clearance to perfection.