You just need to make sure you are loosing the lock nut and then tring to trun the adjusting screw. If you are already doing this then all I can say is you must try harder or if you are afraid you are going to break something than take it to a shop. But it should not be hard to turn after the lock nut is loosened.
i had the same problem before too but it was on a different kind head. i just used force and it broke loose but i ended up slicing my pinky really bad because it ran across some sharp metal, almost to the bone.
we use a specail tool at honda that holds the nut so we turn the screw. Try snap-on or napa
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2007 dodge ram hemi sport-the tow/dd
1993 Civic HB-h22 with type s pistons, 125 shot, and some other goodies
1989 CRX(in the works)-h2b plus maybe some spray, or some boost