[bb400ho]

someone changed the rocker studs and nuts in the 69 gto im working on. i was getting checking out a miss and fornd #8 cylinder had no compression. after checing it out neither the intake or exhaust valve close all the way when the other is open. if i back the rocker studs off a little the compression comes in line with the other cylinders. are the rocker studs are larger than the originals and the nuts look like lock nuts. are these adjustable like the chevies? the nut on the left is the new one the other are the nuts i found in a box withe the old studs.
thanks bryan