Symptoms of a Worn Camshaft: A Comprehensive Guide for DIY Enthusiasts

A worn camshaft can lead to a range of issues in an engine, from decreased performance to complete engine failure. Understanding the symptoms of a worn camshaft is crucial for any DIY enthusiast or mechanic to diagnose and address the problem effectively. In this comprehensive guide, we’ll delve into the specific symptoms, measurements, and observations that can help you identify a worn camshaft.

Audible Symptoms: Identifying the “Squeak Squeak Squeak”

One of the most common symptoms of a worn camshaft is a distinct “squeak squeak squeak” noise that follows the engine’s RPM. This noise is similar to a belt squeal and can be heard using a mechanic’s stethoscope, which can help you pinpoint the location of the issue to the middle of the passenger valve cover.

This noise is caused by the roller of the lifter sliding across the cam lobe, instead of rolling as it should. To confirm this, you can remove the rocker and pushrod, leaving the lifter in place, and then start the engine. If the engine runs smoothly, the issue is likely with the lifter or camshaft.

Visual Inspection: Examining the Cam Lobes

A visual inspection of the camshaft can reveal significant wear and tear. In the case of a bone stock LM7 engine with 150,000 miles, three of the lobes on the camshaft had severe pitting and fatigue, but only over the nose of the lobe. Three other lobes were starting to show signs of pitting, again, only across the nose.

It’s important to note that this type of lobe failure is typically associated with coil bind, which should not be an issue in a bone stock engine. The opening and closing ramps of the camshaft should look fine, with no signs of valve float, bounce, or excess loads during the opening and closing phases.

Measuring Valve Stem Depression

To further diagnose a worn camshaft, you can use a dial indicator to measure the valve stem depression. The failed portion of the lobe is typically only across the nose, with a slight bias towards the closing side. The rollers in the lifters should all roll fine, but if the #4 intake lifter shows signs of the roller sliding across the cam lobe, it’s a clear indication of wear.

Quantifiable Data Points

Here are some key data points and measurements that can help you identify a worn camshaft:

Symptom	Measurement
“Squeak Squeak Squeak” Noise	Follows engine RPM, can be heard with a mechanic’s stethoscope
Cam Lobe Pitting/Fatigue	Severe pitting/fatigue on the nose of the lobes, with some lobes starting to pit
Valve Stem Depression	Failure only across the nose of the lobe, with a slight bias towards the closing side
Lifter Roller Sliding	#4 intake lifter shows signs of the roller sliding across the cam lobe

Additional Observations

In the case of the bone stock LM7 engine, the lifters all still rolled just fine, with no wobbles, slop, or grit. This suggests that the issue was specific to the camshaft, rather than the lifters themselves.

It’s also important to note that the opening and closing ramps of the camshaft looked fine, with no signs of valve float, bounce, or excess loads during the opening and closing phases. This indicates that the issue was localized to the nose of the cam lobes.

Conclusion

By understanding the specific symptoms, measurements, and observations associated with a worn camshaft, DIY enthusiasts and mechanics can effectively diagnose and address the problem. Remember to always use a mechanic’s stethoscope, perform visual inspections, and take precise measurements to identify the root cause of the issue. With this comprehensive guide, you’ll be well on your way to maintaining the health of your engine’s camshaft.

Reference:
– LS1Tech Forum: Cam Lobe Failure Analyses
– Corvette Forum: What are the Symptoms of a Worn Cam Lobe?
– TDIClub Forum: Official VW Response on Camshaft Wear Using 5W-30 Synthetics