Re: Ford 302 VALVE ADJUSTMENT...HELP!
Thiose systems are called "set distance" types, they use a bottleneck stud and special champhered nut, and, they torque down to 20 ft/lbs torque after they hit bottom. Now, Ford has different length push rods, in .060 differences over the median length, to "set the distance" if the median push rod doesn't work correctly. The only way to check if the valve train is good, is to completely collapse the rocker arm into the lifter, and read the distance between the valve stem pad on the rocker, to the stem end. If I remember doing my Ford stuff right, the distance should be .210 +/- .030. To change the valve adjustment, change the length of the push rod.
Some people just tell you to double nut the studs, but that makes for a weaker valve train at the bottleneck on the stud. Poly-Loks are worse, as they will not stay locked down unless the top of the stud is ground flat, and not left with the concave divot in them.
Of course, if the block and/or heads have been decked/cut, and/or a different thickness head gasket has been used, the whole valve train setup procedure must be gone over again, and the correct push rod selected, for EVERY VALVE. If this isn't done, or not done correctly, the lifter will not have its plunger centered in the body, can hold a valve open, or have too much clearance.
As I said, people that do not understand the bottleneck stud systems, and recommend just using a jamb nut, left up the stud from the bottleneck, are just asking for stud breakage at the neck down point of the stud.
That's just the way Ford decided to do it, not a particularly good way to go about getting the valve train/rocker arm geometry correct.