Hydraulic Roller Lifters: How They Work & Why They Fail
Small Parts With a Big Job Inside Your Engine
Hydraulic roller lifters help transfer camshaft motion
through the valvetrain while maintaining proper operating
clearance. When a lifter, guide or supporting component
fails, the result can quickly become much more than an
annoying ticking noise.
A hydraulic roller lifter rides on the camshaft and
transfers the cam's movement through the pushrod and
rocker arm so the engine's valves can open and close.
The roller wheel reduces sliding friction against the
camshaft lobe, while the hydraulic mechanism inside the
lifter helps maintain the proper relationship between
the valvetrain components.
Inside the Valvetrain
Four Parts of the Lifter's Job
Camshaft Contact
Follow the Cam Lobe
The roller at the bottom of the lifter follows
the shape of the camshaft lobe as the cam rotates.
Valve Motion
Transfer the Movement
Lifter movement is transferred through the pushrod
and rocker arm to control when the valve opens
and closes.
Hydraulic Control
Maintain Proper Preload
The hydraulic mechanism helps the valvetrain operate
with the proper internal preload instead of requiring
a constant manual lash adjustment.
Roller Design
Reduce Sliding Friction
Rather than sliding directly across the cam lobe,
the roller wheel turns as it follows the
camshaft profile.
Lifter Failure
A Lifter Problem Can Affect the Whole Top End
Problems with lubrication, contamination, worn guides
or damaged internal components can interfere with
normal lifter operation.
Ticking
Abnormal valvetrain noise can be one early sign
that a lifter or related component needs attention.
Misfire
A lifter that no longer operates correctly can
affect valve movement and cylinder performance.
Roller Damage
If the roller stops rotating correctly,
camshaft damage can follow.
Guide Wear
Worn lifter guides can allow unwanted lifter
movement or rotation.
GM AFM / DOD Systems
Why Oil Control Matters
Oil Pressure and Clean Oil Are Critical
Some GM engines use special lifters as part of Active
Fuel Management or Displacement on Demand systems.
These systems rely on controlled oil pressure to change
lifter operation.
Restrictions, sludge, contamination or wear within the
oil-control system can contribute to improper lifter
operation. That is why diagnosis should include more
than simply replacing the noisy part.
Installation Matters
Three Things to Check During Lifter Replacement
1
Inspect or Replace the Lifter Guides
Worn guides or trays can allow the lifter to rotate
or move improperly. The condition of the guide system
should be checked whenever lifters are replaced.
2
Verify Lifter Preload
Correct pushrod length and lifter preload are important
to proper hydraulic lifter operation. Component
specifications should be checked before final assembly.
3
Check the Entire Valvetrain
A failed lifter may not be the only damaged component.
Inspect the camshaft, pushrods, rocker system and
related parts before putting the engine back together.
Think Like an Engine Builder
Match the Lifter to the Complete Combination
Camshaft, Lifters, Pushrods and Springs Work Together
A hydraulic roller lifter should never be considered
by itself. Camshaft profile, spring pressure, pushrod
length, rocker geometry and intended engine use all
influence how the valvetrain performs.
Hydraulic lifter designs, preload requirements and
valvetrain components vary by engine. Always confirm
the specifications for the engine, camshaft and lifters
being installed before final assembly.
CarDudes Racing & Performance
Build the Valvetrain as a Complete System
Keep moving through the CarDudes Racing & Performance
guides for more on race parts, traction and
race-engine building.
