No, I don't know how to do that. I'm checking Youtube for a video, it appears a special tool is needed to lift the spring, only then insert can you insert a feeler gauge. Have you ever done this job? Any tips?
You shouldn't be using any kind of tool to compress the valve springs unless you are taking out the valves. What you're doing is adjusting the clearance between the top of your valve and your rocker arm. You do this when the springs are fully extended/valve fully closed
I always checked mine by substituting with a known good one that was always around the shop. Coils can be weird in their failure modes so swapping out always worked best for me.
The 8n has a flat head, no rocker arms. I'm guessing the clearance is between the lifter and the valve stem.
I did that.
Not yet, I've just seen a youtube on how to do that and will check it as well.
If checking your valve clearance, is more involved than you want to deal with, you could do, as an alternative troubleshooting check, a compression test, while it’s hot. You’d have to pull the plugs out quickly after stopping it, as to get your readings while it’s still hot. A cylinder with inadequate clearance will read low compression
True only if no hardened valve seats & clearance gets tighter. With hardened valve seats clearance opens up and compression is not affected