That makes sense to me. The engine is a 400 sbc with a mild comp cam, 256H, good heads and intake - Trick Flow 23 degree with an RPM Performer and 700 Edlebrock Carb and 1.6:1 aluminum roller rockers.
With the lifters set the way they were, at zero lash, the car ran fine but the valve train always seemed a little noisy. Now that they are adjusted down 7/8 of a turn the valve train is quiet and the car feels more responsive at all RPM ranges.
It is hooked to a 700R4 converted to nonelectric and I don't normally shift it manually so the engine does not get over-revved, it is more of a torque monster.
Thanks for your explanation.