Stock Hydraulic Lifter Preload Spec?

mopowers said

I'm wondering if I could just measure the range of travel in the lifter and split the difference, or is there an actual recommended range?

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I alwasy assumed that this is typically how the factory would set this up. But I suspect they would measure a whole kabooble of them, not just one or 2. The top position of the piston travel is predicable, but the bottom of the piston travel is not necessarily so well defined.

For performance, folks typically are going to reduce the preload. I have always assumed this is to limit the maximum amount of possible lifter pump-up if the valves DO float. So preload numbers like .030 to .040" are not uncommon. My son and I set his 340 Crane cam lifters to .050" preload.

The possible downside of less lifter preload is a longer time of them rattling at start up if they do leak down any.