It is possible to have mechanical valves without the tick. It all comes down to how they are adjusted.
The book number is most likely the largest gap you can run before performance is dropped.
My 270 had the lifter gap numbers changed 3 times in 4 years (CCKW) depending on the motor, cam, and usage.
My Suzuki Boulevard had mechanical lifters... adjusted every 10k miles... It would take a while but you could adjust the tick out of it. Most ppl live with the ticking as there is no harm in it, and even if you did find the sweet spot for a quiet train, it won't last long.
