Why is the exhaust valve lash generally greater than the intake valve lash?

Why is the exhaust valve lash generally greater than the intake valve lash?

• A. Because there is increased heat on the exhaust valves
• B. Increased exhaust valve wear due to higher temps
• C. Higher intake temperature
• D. Valve timing differences

Answer: (C)

Valve lash changes with temperature because metal expands when heated. Exhaust valves run much hotter than intake valves, since the exhaust gas leaving the combustion chamber is very hot. That heat causes the exhaust valve stem and related parts to expand more, increasing the clearance to the rocker or cam follower when the valve is closed. The intake valve operates in cooler air, so it expands less and its lash is smaller. So the hotter exhaust side naturally ends up with greater lash.

Valve lash changes with temperature because metal expands when heated. Exhaust valves run much hotter than intake valves, since the exhaust gas leaving the combustion chamber is very hot. That heat causes the exhaust valve stem and related parts to expand more, increasing the clearance to the rocker or cam follower when the valve is closed. The intake valve operates in cooler air, so it expands less and its lash is smaller. So the hotter exhaust side naturally ends up with greater lash.