Well I figured my valves probably should be adjusted, and I need to get under there anyway and find out whether if my crank pulley will come loose with an impact wrench or if i'm gonna have to buy the crank pulley tool, so I figured tomorrow i'll get under the hood and adjust my valves...

My question is, on the spec ranges for valve adjustment, should I just try to get them as close to the middle of the range as possible, or would there be a slight performance advantage to adjusting them to one end of the range or the other? If so, which end of the range should I adjust it too?

 

It doesn't matter much. You want to be absolutely sure they are not too tight, as then after the engine warms up, it could go to less than zero clearance. That means the valve is being held slightly open when it should be closed. It will cause poor performance, especially at idling, as well as valve damage from gases blowing past it.

Too loose means they will still be noisy, performance may be reduced a tiny bit because they don't open quite as far, but mostly the engine will be noisy.

 

so basically for best accuracy i should adjust them to the middle of the range and that's all i should worry about

 

Trust, when I adjusted my valve clearance, I did exactly what you said. I used a feeler gauge thickness that was precisely in the middle of the range mentioned in the service manual. My engine continues to run fine.

One question is whether you adjust the valve clearance before or after replacing the timing belt. I did the adjustment afterward, though I don't know whether it really matters. Just make sure the engine is stone cold.

 

Yea, I did it with the engine cold. I haven't done the timing belt yet, but it shouldn't matter as long as you make sure the cam gear is in the right position for each cylinder, instead of judging by the crank pulley.

I did it today and the engine seems to run a little smoother.
Every valve's clearance was about .6mm too much! Definitely a lot better now.