Back in the day when these were in OEM applications they weren't getting more than 10,000 miles before the valvetrain would begin making clicking and clacking noises. Many valve jobs done under Ford Factory warranty to remedy the problem. It wasn't until it was found to be the chroming process on the valve stems that was actually the problem. The stems were somewhat rough (you could feel it with a thumbnail). The valve guides were being heavily worn prematurely, causing increased valve guide clearance, which led to unwanted valve train noise. This held true for all the canted valve Fords 351,400,429,460. Took a while for engineers and suppliers to figure it out. It was a pain to face a customer that had bought a new car and had this going on 8 months later
