Which procedure is used to check dry lifter clearance?

Which procedure is used to check dry lifter clearance?

• A. Extend the lifter and measure clearance with tappet on base circle.
• B. Collapse hydraulic lifter and measure clearance between rocker arm and valve stem with tappet on base circle.
• C. Use a dial indicator while lifter under load.
• D. Remove lifter and measure its diameter.

Answer: (B)

Dry lifter clearance is measured by removing the hydraulic action so you’re seeing the true mechanical gap. To do this, collapse the hydraulic lifter and take the measurement with the tappet on the cam’s base circle. This position ensures the cam isn’t lifting the valve and the lifter isn’t under oil-pressured preload, so the gap you read between the rocker arm and the valve stem reflects the actual clearance that must exist when the lifter is in its collapsed state. That’s why this method is preferred: it isolates the mechanical clearance from oil pressure and lifter preload, giving a reliable “dry” reading. Extending the lifter, measuring under load, or removing the lifter to measure its diameter don’t isolate that true valve-stem clearance and can lead to incorrect conclusions about the lash.

Dry lifter clearance is measured by removing the hydraulic action so you’re seeing the true mechanical gap. To do this, collapse the hydraulic lifter and take the measurement with the tappet on the cam’s base circle. This position ensures the cam isn’t lifting the valve and the lifter isn’t under oil-pressured preload, so the gap you read between the rocker arm and the valve stem reflects the actual clearance that must exist when the lifter is in its collapsed state.

That’s why this method is preferred: it isolates the mechanical clearance from oil pressure and lifter preload, giving a reliable “dry” reading. Extending the lifter, measuring under load, or removing the lifter to measure its diameter don’t isolate that true valve-stem clearance and can lead to incorrect conclusions about the lash.