Why would a camshaft wear out or break?

Home

Tech

Why would a camshaft wear out or break?

Editing Date：2025-09-03

Common Camshaft Failures and Causes

The camshaft itself is rarely to blame when it fails. What most people claim as camshaft failure is usually 1 of 4 things:

•	Excessive wear
•	Mechanical interference
•	Broken pieces, or
•	A cracked camshaft

Excessive Wear

This usually refers to cam lobes wearing out too quickly. It is often the result of improper camshaft break-in. Follow these links for more information:

•	Flat Tappet Cams vs. Roller Cams
•	Break-In Procedure for Flat Tappet Cams
•	Break-In Procedure for Roller Cams

Cam lobes can also wear quickly when using high Valve Spring Pressure. Some high performance race engines require very high spring pressures to accommodate high-lift cams. These high spring pressures will cause the cam to wear faster than normal. These engines, however, are built for performance, rather than longevity.

Mechanical Interference

When moving parts are not given adequate clearance, things can start to break. Damage can result from excessive heat build-up, limited range of motion, or parts crashing into each other.

Follow these links to learn more about common areas of interference in the valvetrain:

•	Valve Spring Coil Bind
•	Valve Spring Retainer to Valve Stem Seal (or Valve Guide)
•	Piston to Valve
•	Rocker Arm Slot to Stud
•	Camshaft End Play

Broken Pieces

In some cases, the dowel pin (or key) will break off the end of the camshaft. This pin sits where the timing gear is mounted. It is used to align the gear on the shaft.

Possible causes of a broken pin/key include:

Mounting bolts not torqued properly.
	Could be too tight or too loose.
	Could lack Thread Locking Compound.
	Always follow manufacturer's instructions.

Using sub-standard hardware.
	New bolts and washers can stretch or compress during service. This changes the torque value.
	Always use either the hardware provided by the manufacturer or equivalent (or higher) grade hardware.

Mechanical interference that suddenly stops the camshaft from spinning.
	See "Mechanical Interference" section above.

A Cracked Camshaft

In rare cases, the camshaft itself will actually crack and break. This can be caused by:

A defective camshaft,
Another part of the engine (e.g. a connecting rod) coming loose and striking the cam, or
Rough handling during shipping or installation that causes unseen damage, like a crack.
	Unseen damage can escalate once the engine is assembled and begins to run.