Engine noises can be a headache for vehicle owners, especially when they originate from the valve springs. These noises can range from a slight ticking to a loud knocking, and they can indicate various issues, such as worn-out springs, incorrect installation, or even engine damage. In this guide, we will focus on diagnosing engine noise from valve springs, providing measurable, quantifiable data to help you understand the problem better.
Valve Spring Noise: Causes and Characteristics
Valve spring noise is often characterized by a ticking or tapping sound that increases with engine RPM. The noise can be caused by several factors, including:
- Worn-out valve springs: Over time, valve springs can lose their tension and begin to wear out, leading to a ticking or tapping noise. The spring rate of a worn-out valve spring can decrease by as much as 20-30%, causing the spring to become too soft and unable to keep up with the valve’s motion.
- Incorrect installation: If the valve springs are not installed correctly, they can cause noise due to improper seating or misalignment. The installed height of the valve springs should be within the manufacturer’s specified range, typically between 1.80 and 1.90 inches.
- Valve train wear: Wear in the valve train components, such as rocker arms, lifters, and pushrods, can also cause noise. This can lead to increased valve clearances, which can result in a tapping or knocking sound.
- Valve float: Valve float occurs when the valve springs cannot keep up with the valve’s motion at high engine speeds, leading to a bouncing effect that can cause noise. This can happen when the valve spring’s free length is too long or the spring rate is too low, allowing the valve to lift higher than the designed specification.
To diagnose valve spring noise, you can use various methods, such as compression testing, leak down testing, and vacuum testing.
Compression Testing
Compression testing is a method used to measure the engine’s compression pressure. A low compression reading can indicate worn-out valve springs or other issues in the valve train. To perform a compression test, you will need a compression gauge and a spark plug socket. Here are the steps to follow:
- Remove the spark plug from the cylinder you want to test.
- Screw the compression gauge into the spark plug hole.
- Crank the engine and observe the compression reading on the gauge. The compression reading should be within the manufacturer’s specified range, typically between 120-160 psi.
- Repeat the process for all cylinders and compare the readings. If the compression reading for a cylinder is significantly lower than the others, it could indicate a problem with the valve springs or other valve train components.
Leak Down Testing
Leak down testing is another method used to diagnose engine noises. It measures the amount of air that leaks past the valves and piston rings. To perform a leak down test, you will need a leak down tester and compressed air. Here are the steps to follow:
- Remove the spark plug from the cylinder you want to test.
- Connect the leak down tester to the spark plug hole.
- Apply compressed air to the tester at a pressure of 100 psi.
- Observe the leak down percentage on the tester. A leak down percentage of less than 10% is considered acceptable, while a reading above 20% may indicate a problem with the valve springs or other valve train components.
Vacuum Testing
Vacuum testing is a method used to measure the engine’s vacuum pressure. A low vacuum reading can indicate worn-out valve springs or other issues in the valve train. To perform a vacuum test, you will need a vacuum gauge and a vacuum hose. Here are the steps to follow:
- Connect the vacuum gauge to the vacuum hose.
- Start the engine and observe the vacuum reading on the gauge. The vacuum reading should be within the manufacturer’s specified range, typically between 18-22 inches of mercury.
- Compare the reading to the manufacturer’s specifications. A low vacuum reading can indicate a problem with the valve springs or other valve train components.
Valve Clearances
Valve clearances are the gaps between the valve and the rocker arm or camshaft. Incorrect valve clearances can cause noise and affect the engine’s performance. To check the valve clearances, you will need a feeler gauge and a wrench. Here are the steps to follow:
- Remove the valve cover.
- Locate the valve adjustment screws.
- Insert the feeler gauge between the valve and the rocker arm or camshaft. The clearance should be within the manufacturer’s specified range, typically between 0.010 and 0.020 inches.
- Adjust the valve clearance by turning the adjustment screw until the correct clearance is achieved.
Valve Spring Specifications
Valve springs have specific specifications, including spring rate, free length, and installed height. These specifications can affect the engine’s performance and noise level. Here are some typical valve spring specifications:
Specification | Typical Range |
---|---|
Spring Rate | 80-120 lbs/in |
Free Length | 1.80-2.00 inches |
Installed Height | 1.80-1.90 inches |
When replacing valve springs, it is essential to use springs with the correct specifications for your engine. Using springs with the wrong specifications can lead to increased valve train noise, reduced engine performance, and even engine damage.
Conclusion
Diagnosing engine noise from valve springs requires a systematic approach and an understanding of the underlying causes. Compression testing, leak down testing, and vacuum testing are methods that can help diagnose the problem. Checking valve clearances and using valve springs with the correct specifications can also help reduce noise and improve engine performance.
Reference:
– Major valve noise after cams & springs – Supra Forums
– ticking noise after valve springs | Turbo Buick Forum
– Diagnosing Engine Noises – Owners World
– Quantifying valve float – Engine & fuel engineering – Eng-Tips
– Noisy” valve springs? – LS1TECH – Camaro and Firebird Forum
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