How to Clean and Calibrate Worn Honda Mechanical Valve Trains (Valve Lash Adjustments)
There’s a specific kind of satisfaction that comes from adjusting the valves on a high-mileage Honda and hearing it purr quietly for the first time in years—and the process is more straightforward than you might think if you take it step by step.
You know that feeling when you’re at a stoplight, and your Honda’s engine sounds more like a sewing machine than a smooth-running motor? That clicking and tapping is the sound of valves that need attention. The mechanical valve train in older Honda engines is designed for precision, but as components wear and clearances change, that ticking noise and lost performance are your engine telling you it’s time for a little TLC. Here’s how to bring that valve train back to its quiet, efficient best.
What’s a Valve Lash, and Why Does It Matter?
A valve train consists of the camshaft, rocker arms, and valves working together. The “valve lash” is the small gap between the rocker arm and the valve stem that allows for heat expansion . Over time, this gap can change due to wear and tear.
- Too loose, and you’ll hear an excessive clicking or tapping noise .
- Too tight, and the valve won’t close completely, causing a loss of performance, hard starting, and over time, can burn the valve or damage the camshaft .
Step 1: Gather Your Tools and the Correct Specs
Before you start, you need the right tools and the correct clearance specifications for your engine. Using the wrong specs will lead to poor performance or engine damage.
Essential Tools
- Feeler Gauges: These are your primary measuring tool. You’ll need a set that includes the specific clearance sizes for your engine .
- Valve Adjustment Tool: This specialty tool is a lifesaver. It’s usually a socket with a built-in screwdriver slot, allowing you to hold the adjustment screw in place while you tighten the lock nut with a wrench .
- Basic Hand Tools: 10mm wrench or socket, flathead screwdriver, and ratchet with extensions .
- Silicone Sealant: For re-sealing the valve cover .
Finding Your Specs
The exact valve clearance depends on your specific engine. Always check your service manual. Here are some common examples:
| Engine | Intake Clearance (Cold) | Exhaust Clearance (Cold) |
|---|---|---|
| D-Series (Most) | 0.007″ (0.18 mm) | 0.009″ (0.22 mm) |
| B16A / B18C | 0.006 – 0.007″ | 0.007 – 0.008″ |
| H22A | ~0.008″ | ~0.008″ |
| K-Series | 0.008 – 0.010″ | 0.010 – 0.011″ |
Step 2: Clean the Valve Train
While you have the valve cover off, it’s the perfect time to clean everything up. A clean valve train allows you to see any potential problems and ensures smooth operation.
- Remove the valve cover and its gasket. Always replace a valve cover gasket if it’s old and brittle .
- Use a clean rag and a solvent like brake cleaner to wipe down the camshaft, cam caps, and rocker arms .
- Pay special attention to the oil spray bars. If they are clogged with sludge, clean them thoroughly to ensure oil reaches the valvetrain .
Step 3: Set Cylinder #1 to Top Dead Center (TDC)
The engine must be stone cold. Ideally, let it sit overnight before starting . The adjustment must be done on a cold engine to get accurate measurements .
- Remove the spark plugs. This makes it much easier to turn the engine by hand .
- Place the car in 4th gear (if manual) and rotate the front wheel to turn the engine over. You can also rotate the crank pulley using a socket and breaker bar.
- Align the “UP” mark on the cam gear so it points straight up. This indicates that cylinder #1 is at TDC on its compression stroke .
Step 4: Adjust the Valves for Each Cylinder
The firing order is 1-3-4-2 . At TDC for cylinder #1, both cam lobes for that cylinder should be pointing upward and the rocker arms should be completely at rest .
- Check the current clearance: Insert the correct feeler gauge for the valve (intake or exhaust) between the cam lobe and the rocker arm. There should be a slight drag. If the gauge slides in too easily or won’t fit at all, you need to adjust .
- Loosen the lock nut: Use your 10mm wrench or valve adjustment tool to loosen the nut on top of the rocker arm .
- Adjust the screw: While the nut is loose, use a flathead screwdriver to turn the adjustment screw. Turning it clockwise tightens the clearance (decreases the gap). Turn it counterclockwise to loosen it (increase the gap) .
- Lock it down: Once you have the correct feeler gauge sliding with that slight resistance, hold the adjustment screw firmly with your screwdriver and tighten the lock nut .
- Double-check: After tightening, recheck the clearance with your feeler gauge. The tightening process can alter the gap slightly, so it’s essential to verify. The 0.008″ feeler should not fit if you set it to 0.007″ .
Rotating for Other Cylinders
- Cylinder #3: Rotate the crank so the “UP” mark on the cam gear faces the front of the vehicle .
- Cylinder #4: Rotate so the “UP” mark faces downward .
- Cylinder #2: Rotate so the “UP” mark faces the rear of the vehicle .
Step 5: Reassembly and Final Checks
- Clean the mating surface of the cylinder head and the valve cover .
- Install a new valve cover gasket if you haven’t already.
- Apply silicone sealant to the sharp corners where the distributor and cam pass through the valve cover to prevent oil leaks .
- Carefully reinstall the valve cover and torque the bolts to 84 inch-pounds. These bolts are easy to snap, so use a torque wrench and be gentle .
- Reconnect everything and start the engine.
A Note on Wear
If you are replacing worn components like springs or retainers, you will still need to check the valve guides. You can measure radial play with a dial indicator and check the valve stem diameter against the spec in your service manual to ensure they are in good condition .
Frequently Asked Questions
What are the symptoms of needing a valve adjustment?
The most common symptom is a clicking or tapping noise from the top of the engine that gets louder as the engine revs. You might also notice a loss of performance, a rough idle, or poor fuel economy .
Can I adjust the valves while the engine is hot?
No. Always perform a valve adjustment on a stone-cold engine. This ensures the clearances are correct, as parts expand when hot .
Do I need a special tool for Honda valve adjustments?
While you can technically do it with just a wrench and screwdriver, a “valve adjustment tool” makes the job significantly easier. It holds the adjustment screw in place while you tighten the lock nut, preventing your setting from being thrown off .
What happens if the valves are too tight?
If the valve lash is too tight, the valve won’t close completely. This can cause a loss of performance, starting issues, and eventually, burnt valves or a damaged camshaft. It’s a very serious problem .
References
For further reading and to verify technical information:
- PakWheels – DIY Valve Adjustment on a 6th Gen Civic
- Hybrid Racing – Honda Valve Lash Adjustment Tools
- IPG Parts – B-Series & K-Series Valve Lash Guide
- Honda-Tech – B-Series Valvetrain Discussion
Have you adjusted the valves on your Honda? What’s your experience—or what challenge are you facing? Drop your questions and tips in the comments below.
