In an engine with hydraulic lifters, when the lifters are completely flat or empty, valve clearance should not exceed which of the following?

In an engine with hydraulic lifters, when the lifters are completely flat or empty, valve clearance should not exceed which of the following?

• A. Zero
• B. A specified amount above zero
• C. A specified amount below zero
• D. Any amount, since lifters aren’t functional

Answer: (B)

Hydraulic lifters maintain zero lash only when they’re pumped up with oil pressure. If a lifter is completely flat or empty, there’s no hydraulic pressure to take up the clearance, so the valve clearance becomes a small positive amount determined by the mechanical parts. The manufacturer specifies a maximum allowable clearance in this unpumped condition. Keeping the clearance within that specified amount above zero ensures the valve train won’t be overly loose once oil pressure returns and the lifter re-pressurizes. If you exceeded that limit, you’d risk excessive lash or erratic valve operation after startup; if you tried to set it to zero or negative clearance, you could invite binding or contact when the lifter isn’t pressurized.

Hydraulic lifters maintain zero lash only when they’re pumped up with oil pressure. If a lifter is completely flat or empty, there’s no hydraulic pressure to take up the clearance, so the valve clearance becomes a small positive amount determined by the mechanical parts. The manufacturer specifies a maximum allowable clearance in this unpumped condition. Keeping the clearance within that specified amount above zero ensures the valve train won’t be overly loose once oil pressure returns and the lifter re-pressurizes. If you exceeded that limit, you’d risk excessive lash or erratic valve operation after startup; if you tried to set it to zero or negative clearance, you could invite binding or contact when the lifter isn’t pressurized.