I don't have a guide to suggest but A loose valve is better than a tight one and since your gonna have to mix and match shims to adjust the valves ( I pretty sure yours uses shims) then shoot for the middle of the range since with heat they'll expand. Mean while, someone may have answered your question already.

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My brother in law is a toyota tech. He says the valves "very rarely" need adjusting. They are a shim bucket design and the shim bucket is what is changed.

Once you properly measure the clearances, you can decide if the shims need to be changed.
You should be more concerned with "tight" valve clearances rather than loose. If a .010" fits tight, then it's not .010" Does the .009" fit loose or have a slight proper drag? If it's quite loose, then you're still OK to call it .010". It may need attention after another 100,000 miles. MAYBE! They don't wear much.

Below are the ranges for the valves. Intakes .006" - .010" and exhaust .010" - .014"

Valve clearance (cold): intake 0.15 – 0.25 Mm (0.0059 – 0.0098 In.) Exhaust 0.25 – 0.35 Mm (0.0098 – 0.0138 In.)

Valves do get both tight and loose as they wear. If the valve seat or valve face wear, the clearance gets smaller. (tight)
If the cam lobes wear, the clearances get larger (loose)

If you need to adjust any valves in the future, adjust to the middle to higher side of the range. Example -Exhaust at .012" or .013"

I think you're still ok and not worth diving in unless you have done something similar before. Your decison...........Good luck.

 

Is the engine making noise? Have poor performance? If it is, when did you notice the change? And how bad was it? These are questions that will tell you if it is worth diving into this repair.

 

I'd start by getting a Metric feeler gauge, and make sure valve lash clearance is measured at TDC where clearance is at its greatest... Mine had all increased, until I reduced all my clearances with 7 new lifters and by switching the other 9 lifters with thicker ones.

 

My 73 Alfa valve and bucket wore exactly .001 in 100k miles I drove it after doing a valve job at 58k. Every valve same amount, so pay attention to the previous post. I wouldn't not touch that unless there was another reason, could go another 100k left alone. The clearance range is broad so none will need to be adjusted unless the head comes off and valve work is performed. Personally if I did it it would be at precisely the max range and if I could get them turned to any dimension (grind valve seats to close setting) I would set every one at max for economy and min for performance (more lift).

 

Leave it alone!

 

I have 409K miles on my 2004 Corolla and I've never bothered with a valve adjustment.

 

This is your perfect opportunity. Just measure your clearances and let us know what they're at.