Using the loaded and unloaded method. If you go to a thicker shim on the unloaded measurement wouldn’t that also affect the loaded measurement.
Yes, no, not really. You're looking for the
difference on the loaded check to find the closer clearance.
If you measure .008" unloaded and .010" loaded, you're looking at a opening clearance of .008" and a closing clearance of .002"
Loaded - Unloaded = Difference / Closer clearance. Opener clearance is simply the unloaded measurement.
Lets say for the sake of this example you're shooting for a opening and closing clearance spec of .004" for both.
If you tighten up the opener clearance first, you simply use a shim .004" larger than the one currently in there that is giving you the .008" clearance.
Once you've installed that .004" larger opening shim, you measure again and now find .004" unloaded and .006" loaded.
So yes, your unloaded and loaded measurements have changed, but the difference is still .002" and therefore your closer clearance has not changed and closer clearance is what you're after with the loaded measurement.
On to the closer clearance. It's still .002" after the opening shim change and you're going for .004". Install a closing shim that is .002" smaller than the one currently in there.
Once you change the closing shim, measure again.
You will now see a unloaded clearance of .004" and a loaded clearance of .008". This means you're at the target spec. .008" Loaded - .004" unloaded = difference / closer clearance of .004".
On the other hand, if you're one who likes to change the closer shim before the opener shim or one who changes both shims at once then there will be variations in what you read. Just remember the only reason you do the loaded measurement at the opening rocker is to find the closer clearance. If you could easily get a feeler gauge between the cam and the closing rocker, there would be no need to do the loaded measurement at all.
Hopefully I haven't confused you here!