What is the valve clearance gap?
The valve clearance gap, also known as the valve lash, is the small gap between the valve stem and the rocker arm or camshaft in an internal combustion engine. This gap is essential for the proper operation of the engine, as it allows the valves to open and close smoothly and efficiently.
What is Valve Clearance Gap?
The valve clearance gap is the distance between the top of the valve stem and the bottom of the rocker arm or camshaft. This gap is necessary to account for the thermal expansion of the engine components during operation. As the engine heats up, the metal parts expand, and the gap needs to be adjusted to maintain the proper clearance.
The valve clearance gap is typically measured in millimeters or thousandths of an inch. The specific gap required for an engine can vary depending on the make, model, and age of the vehicle, as well as the operating conditions and the type of engine.
Why is Valve Clearance Gap Important?
Proper valve clearance gap is essential for the following reasons:
- Efficient Engine Operation: The correct gap allows the valves to open and close at the right time, ensuring efficient combustion and power delivery.
- Valve Wear and Damage Prevention: If the gap is too small, the valves may not close fully, leading to valve wear and potential engine damage. If the gap is too large, the valves may not open fully, reducing engine performance.
- Noise Reduction: The correct valve clearance gap helps minimize engine noise, such as ticking or clicking sounds, which can be caused by improper clearance.
- Fuel Efficiency: Proper valve clearance can contribute to improved fuel efficiency by optimizing the engine's performance.
Regularly checking and adjusting the valve clearance gap is an essential part of engine maintenance, ensuring the engine runs smoothly and efficiently.
What is acceptable valve guide wear?
However, if a purist had the equipment he would measure the i.d. of the guide (all the way through) and the o.d. of the worn part of the valve stem and compare them with the new spec'ns. One manual states total wear of zero to 4 thou wear of the guide is acceptable.
What is the rule of 13 valve clearance?
The “Rule of 13” applies to most 6 cylinder engines, subtract the open valve from 13 to see which one to adjust. To adjust slip the correct feeler gauge blade under the rocker and the top of the valve stem.
What is a proper valve lash?
A critical factor for any engine is the proper clearances between parts. Valve lash is the available clearance (or gap) between the rocker arm and the tip of the valve stem when the lifter for that valve is sitting on the base circle of the cam lobe (when the valve is intended to be fully closed).
What happens if valve lash is too loose?
If the valve lash is excessive then valve lift is lost and in turn, intake port flow drops along with horsepower and torque.
What will too little valve clearance do to the valve?
Too little clearance causes the valves not to fully close when the engine is up to operating temperature, and can cause burned valve tulips and seats.
How to calculate valve lash?
To determine the valve lash, subtract the squish from the desired valve opening lift. The cam in the graph is for a flathead, using squish of 0.002" the valve lash should be 0.0127" or 0.013". The exhaust could be set a couple thousandths larger to allow for thermal expansion.
What is acceptable valve guide clearance?
A general rule of thumb is that intake guides need guide-to-stem clearance of . 001″ to . 003″ and exhaust guides need from . 002″ to . 004″ clearance.
What is the correct valve clearance?
Opinions may vary between piston and valve manufacturers, but a popular consensus is a minimum clearance of . 080-inch for the intake and . 100-inch for the exhaust. The exhaust valve expands more due to heat from combustion, and therefore needs additional clearance.
What is the minimum valve clearance?
What is the minimum recommended clearance?
| Intake | Exhaust |
|---|---|
| 0.080 in. | 0.100 in. |
What happens if the valve clearance is too big?
Too much clearance causes the intake and exhaust valves to open late, impacting performance a bit. It also causes the valves to slam onto their seats, causing unnecessary wear.
