All FE engines originally equipt with a mechanical ("solid") lifter camshaft had adjustable rockers, as a means of setting the proper clearance ("lash") value. This also requires a pushrod of the ball & cup vs. ball & ball design as intended for the hydraulic camshafts with the nonadjustable rocker arms. Applications would include some early 352s, 352HP/PI, 390HP/PI, 406, 427, 428SCJ, not necessarily all, and some others, and some for some unknown reason, but never say never, as there always seams to be an exception.
Most of these consist of a ductile iron rocker arm casting; with a 7/16" x 20t interference thread, hollow stem, 7/16" hex wrench fitment, adjusting ball-stud; a single unit requiring no lock-nut, and cadmium plated to reduce galling. These were/are not good for to many adjustments before the interference thread value is lost, so Ford offered (now obsolete) these ball-studs as service replacements. Or, "back-in-the-old-days" one would hunt in the junk yard for an old "Y" block, which had a solid stem w/ screwdriver slot ball-stud w/ noninterference thread & a hex lock-nut which would retrofit (although heavier) into the FE rocker arm.
The units you describe (utilizing an Allen wrench fitment) would appear to be aftermarket replacements; which, at one time, where available from many vendors, but as of now, are obsolete (N.A.) from most if not all. Scott.
Last edited by pbf777 : 09-09-2016 at 08:34 PM.