Setting valve tappets

[Mark]

I heard a loose tappet on the 151,(I had set them 200 miles before), when checking them cold, the feeler gauge wouldn't go in place, ya the TM says I think, have engine warmed up when setting, so I did it.Still had to loosen the tappets, to get the feeler gauge in, I did this while the engine was running.So could the tappet bolts be defective?They turned hard, (self-locking feature?)
My mechanic thinking is rusty LOL.

[rickf]

They will turn hard, that way they do not loosen in use. Be sure to push/pull in the direction parallel to the arm so you are not trying to bent the rocker arm. I have seen the ends get broken off on them that way. I warm up the engine and then set the valves with it not running, it save me a lot of pain in the arthritic joints in my hands and the valve settings don't know if it is running or not as long as they are set at .015.

[Mark]

Thanks for the feedback

[raymond]

I like to do it with the engine running. It won't spray oil everywhere. And yes, the threads used on the nuts and bolts are interference threads so they won't move once the valves are adjusted. When running at idle, you should just barely be able to slide the feeler gauge. It should not excessively "grab" the feeler, or it is too tight.