[tbirdtbird]

"When the valve is wide open, you can get any wrench made for tappets in there."

Look at the pic. The lifter is all the way up. Precious little body is is exposed to get a purchase on. He needs a very thin wrench to hold the lifter body from turning in order to get a diff. wrench on the locknut. We run into this all the time, especially if the cam has been reground