valve click

[six7teen]

i use to have a miata and it did the exact same thing! i never got a chance of fixing it. but for some odd reason, when i ran a higher test gas, it cut down on the valves tapping a little bit. it might have just been in my head, but it doesnt hurt to try.

[Kaiser]

If your problem reacted to higher octane gas then it probably wasn't valve clatter but rather pinging. There's a difference in cause, though to the untrained (And sometimes even the trained) ear, it can sound extremely similar. A noise coming from the valves themselves should not change when you change the octane in the gas.

If the valves are not opening and closing properly it could be causing pinging by the a/f mix being improper somehow and that would be the only valve problem I can imagine that would react to the higher octane gas. You could have even had a combination of two problems, valve clatter (what remained after you used the higher octane gas) and a pinging problem that could be related or not.

To the OP: straight6 probably hit the nail on the head with his suggestion. Try changing the oil and trying that out, and make sure you put in the exact full amount. Cars with hydraulic lifters can make a horrible racket when they're low on oil, or if the oil isn't flowing properly. Also make sure you're running the proper weights for the temperatures, as the recent cold could be contributing if combined with higher weight oils.

Let us know if you get any changes, maybe it could help us narrow the solution down if nothing else, though TM4.0's idea of having the head cleaned ported & polished is a great idea by itself. It really will make a noticable difference in how the car responds.