Magnum engine's got a tapping sound....

Mine's a full Magnum motor. The valvetrain was used. I bent a pushrod as a result of a sheared rocker bolt, and I put in two new pushrods. They're exactly the same size as the stock pushrods. The lifter under the bent pushrod seemed okay, but I only tested it by pushing on it with the pushrod. It had no play. Is there any other way to check a lifter while it's in the head?