How to Spot Damage, Prevent Failure, and Know When to Regrind or Replace
Why the Camshaft Matters
Your camshaft is one of the hardest-working parts inside a diesel engine. It opens and closes the valves in perfect timing with the pistons. Over time, that constant movement causes wear. If caught early, minor wear can be corrected. But if ignored, it can lead to major engine problems. In this guide, you’ll learn how to spot the signs of camshaft wear. We’ll also explain what to do next—whether that means regrinding, relining, or replacing the camshaft altogether.
What Causes Camshaft Wear?
Camshafts wear down due to heat, friction, and lack of lubrication. High mileage is one cause, but it’s not the only one. Dirty oil, low oil pressure, and poor oil quality also speed up wear. Improper break-in of a new camshaft can cause damage in just minutes. Incorrect valve lash or spring pressure can increase stress on the lobes. Even normal use eventually leads to gradual surface wear. Understanding these causes helps you prevent future issues.
Recognizing Camshaft Wear Patterns
There are several types of wear you might find on a camshaft, and each tells a story about what’s going wrong inside the engine. Scoring shows up as fine, straight lines running along the lobe or journal, and often comes from dirty oil or metal debris. Pitting appears as small craters or holes on the surface, usually due to corrosion or poor lubrication. Galling looks like smeared or torn metal, which happens when two surfaces rub together with little or no lubrication, often during a dry start. Flaking or spalling means small pieces of metal chip off the surface, which points to material failure or surface fatigue. Lastly, lobe rounding occurs when cam lobes become smooth and rounded instead of having a defined peak, leading to reduced valve lift and weaker engine performance. Each of these patterns indicates something different. While scoring might be minor, galling or lobe rounding usually points to bigger problems that need immediate attention.
Step-by-Step Camshaft Inspection
To inspect and diagnose camshaft wear, start by removing the valve cover and, if necessary, the camshaft itself. Clean off any oil or debris to get a clear view of the surfaces. Under bright light, carefully inspect the lobes and journals for wear patterns. Run your fingers along the surface—it should feel smooth, not rough or grooved. Use a micrometer or dial gauge to measure lobe lift and compare the numbers to your engine’s factory specs. Watch for uneven wear between lobes, which could indicate problems with lifters or rocker arms. Always check the condition of lifters, followers, valve springs, and rocker arms during your inspection. If just one lobe is worn, the problem may be isolated. If all lobes show wear, your issue may be related to oil pressure or lubrication.
Decision Time: Regrind, Reline, or Replace?
Once you’ve identified the type of wear, it’s time to decide what to do about it. If the lobes are still within factory spec but have minor scoring or pitting, a light polish or camshaft regrind might be all you need. When the wear is moderate but not too deep, regrinding is still a good option—especially if the camshaft is structurally solid and the journals are in good shape. However, if you spot deep gouges, cracks, heavy galling, or material flaking, the damage is likely too severe. In these cases, replacement is the safest route. On the other hand, if the lobes are in good shape but the cam journals are worn out, relining could be a solution. This process installs new sleeves or bearings into the journals to restore fitment and oil control. But if multiple areas are damaged, replacement is usually the better long-term option. When in doubt, a reputable machine shop can help you decide.
When Regrinding Makes Sense
Camshaft regrinding can be a great way to restore performance without the cost of full replacement. It works best when the camshaft is free from cracks or warping, and when wear is limited to the lobe surfaces. During regrinding, a specialist cuts new lobe profiles onto the camshaft, often reducing the base circle slightly. This change may require longer pushrods or valve lash adjustments, but a reground camshaft can still offer excellent reliability and power. Regrinding is also ideal for custom cam profiles, where you want to tweak timing or lift for a specific application. As long as the journals are still in spec and the camshaft is physically sound, regrinding is a smart way to bring an old cam back to life.
Understanding Camshaft Relining
Relining is less common than regrinding, but it’s a valuable technique in the right circumstances. It’s mainly used when the camshaft’s journals are worn, but the lobes remain in good shape. Relining involves inserting precision-machined sleeves into the journal areas. This brings the journals back to spec and helps restore proper oil pressure and alignment. It’s especially useful for hard-to-find camshafts, older engines, or heavy-duty diesel applications where replacements are costly or unavailable. However, relining must be done with extreme accuracy. If the new liners aren’t perfectly aligned, the camshaft won’t rotate properly—and you could end up with more wear or even a catastrophic failure.
Signs It’s Time to Replace
Sometimes, repairing a camshaft isn’t worth the risk. If any lobes are flattened or heavily rounded, or if there are visible cracks, deep gouges, or chunks missing, replacement is the only safe option. A warped or out-of-round camshaft is also a clear sign it needs to go. If the journals have worn past the point of relining, or if the camshaft has already failed and damaged other components, don’t hesitate—replace it. For fleet vehicles or heavy-use applications, the cost of downtime may outweigh the savings from trying to repair. A new camshaft often comes with a warranty and ensures a clean slate, giving you long-term peace of mind.
Tips to Prevent Camshaft Wear
You can extend the life of your camshaft by taking a few proactive steps. Always use high-quality engine oil with the correct viscosity, and change it regularly based on your engine’s workload. Diesel engines are rough on oil, especially those running EGR or turbo systems. During installation of a new or reground camshaft, follow proper break-in procedures using break-in oil that contains zinc or ZDDP. If you’re using a flat-tappet cam, this step is critical. Make it a habit to check and adjust valve lash at scheduled intervals, since improper clearance can cause impact wear. Inspect lifters, pushrods, and rocker arms every time the top end is serviced. A failure in one of these components can destroy a perfectly good camshaft. Finally, avoid long periods of idling. At idle, oil pressure is lower, which limits how well the camshaft is lubricated.
Final Thoughts
A worn camshaft doesn’t always mean the end of your engine, but it’s a sign that something needs attention. By understanding how to recognize wear patterns and properly inspect your camshaft, you’ll be able to take corrective action before things get worse. Whether it’s a regrind, a reline, or a full replacement, making the right decision will save you time, money, and future headaches. Your camshaft plays a central role in how your diesel engine breathes, performs, and holds up under load. Keep it in top condition, and it’ll return the favor mile after mile.