Checking flat tappet lifters primarily involves visual inspection for wear and a functional test to ensure they rotate correctly within their bores.
Why Inspect Flat Tappet Lifters?
Proper functioning flat tappet lifters are crucial for your engine's performance and longevity. They transfer the motion from the camshaft lobes to the pushrods (or directly to the valve stem in some overhead cam designs), opening and closing the valves. Failure to inspect and replace worn lifters can lead to:
- Camshaft Damage: A worn or non-rotating lifter will quickly wear down the corresponding camshaft lobe, leading to costly repairs.
- Valvetrain Noise: Ticking or clattering sounds often indicate excessive clearance or wear.
- Loss of Performance: Worn lifters or cam lobes can result in reduced valve lift, affecting engine power and efficiency.
- Engine Failure: In severe cases, extensive wear can introduce metal debris into the oil, potentially damaging other engine components.
Tools You'll Need
Before you begin, gather these essential tools:
- Basic hand tools (wrenches, sockets) to remove valve covers.
- Flashlight or work light.
- Engine turning tool (a large ratchet and socket for the crankshaft bolt).
- Clean rags.
Step-by-Step Inspection Process
Inspecting flat tappet lifters involves both a visual check for physical wear and a functional check for proper rotation.
1. Visual Inspection for Wear
The most common point of failure for flat tappet lifters is the contact surface with the camshaft lobe.
- Remove Valve Covers: Access the valvetrain by carefully removing the engine's valve covers.
- Position the Cam Lobe: For each lifter you want to inspect, rotate the engine by hand until the corresponding cam lobe is on its base circle (the lowest point of the lobe, where the valve is fully closed). This relieves pressure on the lifter and pushrod, allowing for easier inspection.
- Inspect the Lifter Face:
- Use a flashlight to carefully examine the bottom (cam contact) face of the lifter. This is often done by looking through the pushrod bore if the lifter cannot be easily removed without pulling the camshaft.
- Look for:
- Pitting: Small depressions or holes on the surface.
- Scoring: Grooves or scratches.
- Dishing or Cupping: A concave depression in the center of the lifter face. This is a critical sign of severe wear and often indicates the camshaft lobe is also damaged.
- Uneven Wear: Any inconsistent wear pattern across the face.
- Inspect Lifter Body: While harder to see without removing the lifter, look for any signs of scoring or excessive wear on the sides of the lifter body where it rides in the lifter bore.
2. Functional Check: Lifter Rotation
Flat tappet lifters are designed to slowly rotate within their bores as the engine runs. This rotation ensures even wear distribution across both the lifter face and the camshaft lobe. A non-rotating lifter will quickly "dig" into the camshaft, causing rapid wear.
- Identify Lifter and Pushrod: With the valve covers off, locate the pushrod corresponding to the specific lifter you wish to check.
- Apply Downward Pressure: Exert downward hand pressure on the pushrod corresponding to the lifter and lobe you want to check. This helps to simulate the normal operating pressure and ensure proper contact.
- Rotate the Engine: While maintaining pressure, rotate the engine by hand at least one entire revolution.
- Observe Lifter Rotation: You should see the lifter rotate about 360 degrees per each complete engine revolution. If a lifter does not rotate or rotates only partially, it indicates a problem. This could be due to a worn lifter face, a damaged cam lobe, or an issue within the lifter bore.
Signs of Failing Flat Tappet Lifters
Recognizing symptoms early can prevent more significant damage.
- Ticking or Clattering Noises: A persistent, rhythmic ticking or clattering sound from the valvetrain, especially when the engine is cold, can indicate a worn or stuck lifter.
- Engine Misfires or Rough Idle: If a lifter fails to open a valve completely or at the correct time, it can lead to misfires, reduced power, and a rough idle.
- Loss of Engine Power: A "flat" cam lobe caused by a worn lifter will reduce valve lift and duration, significantly impacting engine performance.
- Metal Debris in Oil: During an oil change, inspect the drained oil for metallic flakes or glitter, which can be a sign of severe wear on the camshaft and lifters.
- Oil Pressure Issues: While less direct, severe valvetrain wear can sometimes contribute to oil pressure problems.
When to Check Your Lifters
- During Camshaft Break-In: This is critical for new camshafts and lifters. Regular inspection during the initial break-in period ensures proper seating and lubrication.
- When Troubleshooting Valvetrain Noise: Any new or persistent ticking/clattering should prompt an investigation.
- During Major Engine Service: If you have the valve covers off for other maintenance (e.g., valve adjustment, head gasket replacement), it's a good time to inspect the lifters.
Note: If you find any signs of dishing, severe pitting, or a lifter that doesn't rotate, both the lifters and the camshaft should be replaced. Replacing only the lifters on a worn cam will lead to rapid failure of the new lifters.
