I think I figured it out (sometimes search does yield some results), if the lifter collapses, then the piston is pushing the valve causing the lifter to collapse (obviously not enough clearance). Is this correct?
Hydraulic lifters use oil to "pump up" during operation, hence the "hydraulic" part of the name. If the engine is not running, the plunger in the lifter will push further down inside, which will create less valve lift when checking your clearance; therefore, making it look like you have more clearance than you actually do.
Take the retaining clip out of the top of the lifter. There will be three pieces held inside, one of the three pieces is a spring, so make sure you don't let it fly out. Take the top part out, then you will find the second part is the plunger, followed by the spring. Leave the spring out, turn the plunger upside down and place back inside the lifter, then replace the top part of the lifter. You can leave the retainer clip out. You have now made the lifter solid and you can use it to check your clearance when turning the motor over by hand.
After your done, reassemble lifter like before and reinstall retaining clip.
Hydraulic lifters use oil to "pump up" during operation, hence the "hydraulic" part of the name. If the engine is not running, the plunger in the lifter will push further down inside, which will create less valve lift when checking your clearance; therefore, making it look like you have more clearance than you actually do.
Take the retaining clip out of the top of the lifter. There will be three pieces held inside, one of the three pieces is a spring, so make sure you don't let it fly out. Take the top part out, then you will find the second part is the plunger, followed by the spring. Leave the spring out, turn the plunger upside down and place back inside the lifter, then replace the top part of the lifter. You can leave the retainer clip out. You have now made the lifter solid and you can use it to check your clearance when turning the motor over by hand.
After your done, reassemble lifter like before and reinstall retaining clip.