I was wondering about the various valve adjustment methods, including the companion cylinder method.

On an engine that is already operating properly, wouldn't it be possible to just pull the valve cover off, feel around for whatever rocker arms have slack in them and adjust those 3 or 4 rockers? Then rotate the engine some random amount and adjust whichever ones have no tension on them. Keep a note on which ones you've done and stop after you hit them all.

If the rocker arm can be rattled by hand it means there's no tension on it and that its valve is closed, right? If so, it's ripe for adjustment.

Does this make sense? Is my thinking correct?

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)