Valve lifter question.

Dartley, I agree with Rumble that most likely this problem was not caused by a small radiator / overheat problem. You would have seen other signs and symptoms other than just one lifter "ticking" if you had run it hot enough to matter. I think probably just defective lifter from the get go. Not sure what brand lifters, but you can get bad parts under any name. Just my .02.