Engine has approximately 50K on it since a rebuild. Not sure how well it was rebuilt..... At start up it makes a noise like rod knock but it goes away after ~2-3 seconds - enough time to build oil pressure. The timing chain guides looked intact when I adjusted the valves approx. 10K ago. Any other ways to rule out (or in) the timing chain guides/tensioner/chain w/o taking off the valve cover?

Brian