Issues when 'Clay-ing' an Engine with Hydraulic Lifters?

[66fastback]

I know this may sound a bit odd, but I seem to remember something about being able to convert your old worn out hydraulic lifters into a solid lifter for just these sort of uses. I think it had something to do with removing the clip, taking the lifter apart, and removing the spring. I know I've done it before, but it's been years ago. I think you flip the plunger part upside down when you put it back in. Makes a handy part for checking cam specs, but I never used it for piston/valve clearance checks. Hope you can understand this, I'm really tired and not sure if I'm making any sense or not.