Are you SURE on the lifter pre-load? What kind of rockers? How many turns past 0 lash? If you're 1 full turn past 0 lash thats .042 pre load assuming a standard 24 thread per inch adjuster. That could be too much for your setup. I'd try 1/2 turn (.020)
Don't forget that the rocker ratio will end up making he valves open more than just the thread increase or decrease with the adjuster changes, which can affect the pressures on the lifters
I like to use right at 1/4 to 1/3 turn preload on 3/8 adjusters from zero lash at room temps. to start with and go from there with the motor broken in and warmed up
