I used standard inch feeler gauges with .001" difference between the sizes and they worked just fine. The intakes should be .004"-.006" and the exhausts .008"-.010". Don't worry about the 4 decimal place accuracy shown in the manual, its just a conversion from metric values. The most crucial thing I found was developing the proper "feel" with the feeler gauges. There is a subtle difference between the feel of a gauge that fits snugly in the clearance and one that is just a little too thick. If you push too hard with a gauge that is too thick, you can actually get the gauge to slide in the gap and fool yourself (you can actually force the valve open with the gauge!). To develop the "feel", start with a gauge that you know is too thin (e.g. .006 for exhaust
) and step up one size at a time until you feel the gauge start to "pinch". It's a little awkward at first because you have to radically bow the feeler gauge to get it in there, but if you pay attention and repeat it a few times, you'll get it.