advice on measuring valve shims
I am replacing the stock cams in a 2L with a set of Shankle 5417 cams I purchased years ago. The motor also has a Wes Ingram Modified Spica pump. I removed the stock cams and installed the new ones. (The base on the new lobes measured aprox .5mm smaller than the stock cam so I knew I would be ok using the stock shims to get my measurement for the new shims.) The measurements of the shims in the motor don't equal what is available. Shims should be on .025mm increments. Some are real close i.e.. 2.049 etc so I assume that would be 2.050 but a few measure quite off. i.e. 2.141, 1.960, 2.070
Here's my question, in doing my calculations should I round up/down on the shim measurement that is in the motor to the closest .025 and then add the gap measured or do I use the actual measurement. In some cases it doesn't matter because either way it falls within the range of one shim, but in two cases the difference from actual thickness to the closest .025 results in calling for the next thickness. I know I can just purchase a few extra shims to cover the range but I'm curious if this is common or I am I not being accurate with my tools. I's a digital micrometer, I re-zero it often and it accurate to .001mm when checked against my feeler gauge. I cleaned the shims to remove any crud. I really just want to do this once. Oh, and one shim has some scuff marks but none look they have been ground down.
83 GTV-6 3.0L
78 Alfetta Sport Sedan