Don't buy Comp hydraulic roller lifters. Mine lasted a few months. One by one they would collapse and rattle for a while then start working again. The last one to go just wouldn't pump back up. I pulled the lifters and took them apart. The metering plate under the pushrod cup had shattered on several lifters. A small piece of this plate would jam the valve open until it eventually worked it's way past the valve to the bottom of the lifter. The valve is another plate, unlike the lifters in the video Comp have on YouTube which show a ball valve. Comp Cams won't answer my emails.