[rotorwrench]

If a follower to valve clearance check reveals no valves out of adjustment, a person may have to pull the heads and check for piston to head clearance or maybe a small object embedded in a piston top.

I've been running the Johnson solid type cam followers in one of my Mercs for a long time but they were so tight I had to fabricate a tool to hold the tappet while I turn the screw. The Johnson tools were (and should be) inadequate for the job. The screw fit should be very tight in the tappet so a tool or a drilled hole in the follower bore should be required so that the damn things don't try to back off after they run a while. I've heard of folks using a Wick & Lock type of Loctite to hold them but the parts have to be very clean to get the Loctite to work.

Some of the aftermarket ones have some tight adjuster screws and some not so tight. A person might be able to tighten them up by deforming the thread of the screw in some way but that practice could ruin the parts if not performed very carefully.

A lot of small town auto parts stores in areas with a fair amount of farming used to keep the Johnson solids in stock just for the old Ford tractors. That's how I've found several original sets over the years. Sadly, there seem to be less and less auto parts stores like that in the modern era. Top Line Automotive Engineering has the Johnson name now but I haven't tried any of their new products so I can't say yay or nay about them.