Camshaft vs. Crankshaft: What’s the Difference?

A camshaft controls when engine valves open and close, while a crankshaft converts the pistons’ up‑and‑down motion into rotational power that turns the wheels. They are synchronized—typically with a belt, chain, or gears—and in a four‑stroke engine the camshaft rotates at half the speed of the crankshaft. This article explains how each component works, how they differ, and why both are essential to modern engines.

What each part actually does

The following points outline the fundamental job descriptions of the crankshaft and camshaft inside an internal combustion engine.

• Crankshaft: Converts the reciprocating motion of pistons into rotational motion to drive the vehicle’s drivetrain and accessories. It connects to pistons via connecting rods and carries the flywheel or flexplate, balancing counterweights, and often a vibration damper.
• Camshaft: Times and actuates the opening and closing of intake and exhaust valves using lobes that push lifters, pushrods, and rocker arms (OHV) or directly act on tappets/rockers (OHC/DOHC). Its shape and timing critically influence engine breathing, efficiency, emissions, and power.

Together, these roles divide the work of making power: the crankshaft turns power into rotation, and the camshaft lets the engine breathe at the right moments to create that power.

Key mechanical differences

This list details how the two shafts differ in speed, construction, location, and the way they are synchronized.

• Speed and timing: In a four‑stroke engine, the camshaft rotates once for every two crankshaft rotations (a 2:1 ratio). Many two‑stroke engines have no camshaft because they use ports or reed valves instead of poppet valves, though some specialized two‑strokes use cams for exhaust valves.
• Shape and construction: The crankshaft has offset crankpins, main journals, and counterweights to manage heavy torsional loads. The camshaft is a straight shaft with eccentric lobes precisely ground to defined lift, duration, and lobe separation angles.
• Location: The crankshaft sits low in the engine block within the crankcase. The camshaft lives either in the block (OHV/pushrod engines) or in the cylinder head(s) above the valves (OHC/DOHC engines).
• Connection and synchronization: Timing belts, chains, or gear trains link the crankshaft to the camshaft. Variable valve timing (VVT) systems use cam phasers to advance or retard cam timing relative to the crank, optimizing performance and emissions.
• Loads and lubrication: The crankshaft handles high cyclic torsional loads and relies on robust main and rod bearings. The camshaft faces high contact stresses at lobes and followers, demanding clean oil and proper anti‑wear additives to prevent lobe or lifter scuffing.

These distinctions explain why the parts look different, sit in different places, and require different maintenance—even though they must operate in perfect harmony.

How they work together in a four-stroke cycle

The steps below show how the camshaft and crankshaft stay synchronized so valves and pistons never collide and power is produced efficiently.

1. Intake stroke: As the crankshaft rotates and the piston moves down, the camshaft opens the intake valve to draw in the air‑fuel mixture.
2. Compression stroke: The intake valve closes; the camshaft keeps both valves shut while the piston moves up and compresses the mixture.
3. Power stroke: The spark plug ignites the mixture; the expanding gases push the piston down, spinning the crankshaft and producing torque.
4. Exhaust stroke: The camshaft opens the exhaust valve as the piston rises, expelling spent gases before the cycle repeats.
5. Synchronization: The timing set (belt/chain/gears) keeps crank and cam in phase; even slight misalignment can reduce power, trigger fault codes, or cause engine damage in interference engines.

This choreography is why timing integrity is critical: the crank makes the power, but the cam determines when that power is possible.

Symptoms when things go wrong

The following symptoms help distinguish camshaft-related issues from crankshaft-related issues and timing faults that affect both.

• Crankshaft problems: Deep knocking under load, low oil pressure, metal shavings in oil, severe vibration, or a no‑start condition from a failed crankshaft position sensor.
• Camshaft problems: Misfires, rough idle, loss of power, ticking from valvetrain, poor fuel economy, or cam timing codes (e.g., P0011, P0014). A broken timing belt/chain can cause bent valves in interference engines.
• Timing correlation issues: Rattling at startup, check‑engine light with cam/crank correlation codes (e.g., P0016–P0019), sluggish response, and poor drivability, often pointing to a stretched chain, worn guides, or a slipped belt.

Pinpointing the symptom cluster can guide whether the fault lies in the crank assembly, the cam and valvetrain, or the timing system that links them.

Maintenance and longevity tips

These practices help extend the life of both shafts and the timing components that connect them.

• Use the correct oil grade and change it on schedule; clean oil protects cam lobes, lifters, and crank bearings.
• Replace timing belts at the manufacturer’s interval (often 60,000–100,000 miles/100,000–160,000 km); inspect timing chains, guides, and tensioners for stretch or wear.
• Address low oil pressure or oil starvation immediately; it rapidly damages both cam and crank surfaces.
• Listen for unusual valvetrain or front‑cover noises; early attention prevents catastrophic failures.
• Diagnose sensor faults: camshaft and crankshaft position sensors are critical to engine management and can mimic mechanical timing issues when they fail.

Good lubrication and timely attention to the timing drive are the two biggest determinants of cam and crank longevity.

Modern variations and technology

Today’s engines add sophistication to both components to boost efficiency, performance, and emissions control.

• Dual overhead cams and VVT: Many engines use DOHC layouts with cam phasers (VVT/VVT‑i, VANOS, VCT) to vary cam timing dynamically across the rev range.
• Variable valve lift and duration: Systems like Valvetronic, MultiAir, and VTEC alter valve lift or duration, reducing pumping losses and improving power without changing the crankshaft.
• Camless concepts: Emerging systems (e.g., Koenigsegg’s Freevalve) replace the camshaft with electro‑pneumatic or electro‑hydraulic actuators for fully independent valve control.
• Crankshaft designs: Cross‑plane vs. flat‑plane layouts in performance engines tune vibration and exhaust character; forged cranks offer higher strength than cast versions.
• Hybrid integration: Belt‑ or crank‑integrated starter‑generators add torque assist and regeneration directly to the crankshaft, influencing drivability and efficiency.

While their core roles remain, cam and crank technologies continue to evolve, improving drivability, emissions, and reliability.

Bottom line

The crankshaft turns piston motion into rotational power; the camshaft times valve events so the engine can breathe and make that power. They’re mechanically linked and precisely synchronized—typically at a 2:1 speed ratio in four‑stroke engines—so any issue in one often affects the other. Keep oil clean and timing components healthy, and both will usually last the life of the engine.

Summary

A crankshaft is the engine’s primary rotating shaft that delivers torque to the drivetrain; a camshaft is the timed valve‑control shaft that manages airflow in and out of the cylinders. Different in function, construction, location, and operating speed, they work in lockstep to create efficient, reliable power.

Is replacing a camshaft a big job?

Time and effort: Depending on the make and model of your vehicle, replacing a camshaft can be a time-consuming task. It may require several hours of work, including disassembly, inspection, replacement, and reassembly. Additionally, it may require special tools and equipment to complete the job properly.

What happens when a camshaft goes bad?

When a camshaft goes bad, you might notice symptoms like a rough idle, engine misfires, lack of power, a lit check engine light, a loud ticking or tapping noise from the engine, increased fuel consumption, and difficulty starting the vehicle. These issues arise because a faulty camshaft fails to correctly open and close the engine’s intake and exhaust valves, disrupting the engine’s combustion and timing. 
This video explains the common symptoms of a bad camshaft, including engine misfires and noises: 53sKamsiparts Automotive YouTube · Sep 14, 2023
Common Symptoms of a Bad Camshaft

• Rough Idle and Misfires: The camshaft’s timing is crucial for proper combustion. A worn or damaged camshaft can lead to inconsistent valve operation, causing the engine to run roughly and misfire. 
• Engine Performance Issues: You may experience a noticeable loss of power, hesitation during acceleration, and a general lack of responsiveness from the engine. 
• Check Engine Light: A malfunctioning camshaft can trigger sensors, causing the “Check Engine” light to illuminate on your dashboard. 
• Abnormal Noises: A worn camshaft or damaged camshaft bearings can create loud tapping or ticking sounds, especially from the upper part of the engine. 
• Increased Fuel Consumption: Inefficient combustion due to poor valve timing can lead to a drop in your vehicle’s fuel efficiency. 
• Stalling and Starting Problems: Severe camshaft issues can disrupt the engine’s operation, leading to stalling, particularly at low speeds, or difficulty getting the engine to start. 
• Backfiring: Incorrect valve timing can allow unburnt fuel to ignite outside the combustion chamber, resulting in loud pops or bangs from the exhaust or intake. 
• Metal Shavings in Oil: As the camshaft lobes wear down, they can shed metal particles into the engine oil, which can be seen when draining the oil. 

Why It Matters
A bad camshaft is a serious issue that can lead to extensive and expensive engine damage if not addressed promptly. Early replacement can help restore engine performance, improve fuel efficiency, and prevent further harm to related engine components. 
This video explains the importance of a camshaft position sensor and how it relates to engine timing: 57sCar Care CluesYouTube · Nov 6, 2024

Is a camshaft the same as a crankshaft?

No, camshaft and crankshaft are not the same; they are distinct but related engine components with different functions. The crankshaft converts the up-and-down motion of the pistons into rotational power to drive the vehicle. In contrast, the camshaft opens and closes the engine’s intake and exhaust valves at precise moments during the engine cycle.
 
You can watch this video to understand the difference between camshaft and crankshaft: 42sAutomobile basic ideasYouTube · Jan 27, 2025
Crankshaft:

• Function: Converts the linear motion of the pistons into rotational motion. 
• Location: Located at the bottom of the engine. 
• Power Transfer: The rotational power from the crankshaft is sent to the transmission to power the vehicle’s wheels. 
• Relation to Pistons: The pistons are connected to the crankshaft via connecting rods. 

Camshaft: 

• Function: Controls the timing of the engine’s intake and exhaust valves. 
• Location: Typically located near the top of the engine, within the cylinder head. 
• Motion: Uses egg-shaped lobes, called “cams,” to push on the valves, opening them at the right time for fuel and air to enter and exhaust to exit. 
• Relationship to Crankshaft: The camshaft’s rotation is synchronized with the crankshaft’s rotation, usually through a timing belt, chain, or gears. 

How They Work Together:
Both components must work in a precisely choreographed sequence for the engine to operate correctly. The crankshaft provides the rotating force, and the camshaft’s timing ensures that the valves are open or closed at the exact moments to allow for proper combustion within the cylinders.

What is the function of the camshaft and crankshaft?

The camshaft opens and closes the engine’s intake and exhaust valves, precisely controlling the air and fuel mixture into the cylinders and the exit of exhaust gases. The crankshaft converts the linear, up-and-down motion of the engine’s pistons, which is caused by combustion, into the rotational power needed to drive the vehicle. These two components are synchronized by a timing belt or chain and work together to ensure proper engine timing and efficient combustion.
 
Camshaft Function

• Valve Control: The camshaft has lobes that rotate and push on the valves, opening them at specific times during the engine cycle. 
• Optimized Combustion: By accurately controlling when the valves open and close, the camshaft optimizes the four-stroke combustion cycle (intake, compression, power, exhaust) for performance and efficiency. 
• Synchronization: In a four-stroke engine, the camshaft completes one rotation for every two rotations of the crankshaft, ensuring each valve opens only during its designated stroke. 

Crankshaft Function 

• Motion Conversion: The primary function of the crankshaft is to convert the reciprocating (up-and-down) motion of the pistons into rotational motion. 
• Power Transmission: This rotational energy is then transferred to the vehicle’s transmission and ultimately to the wheels, powering the vehicle. 
• Balancing: The crankshaft is designed with balancing weights to smooth out the engine’s operation and minimize vibrations. 
• Auxiliary Power: The crankshaft also serves to power other engine components, such as the alternator and water pump. 

How They Work Together

• Timing System: A timing belt or chain connects the crankshaft and camshaft, ensuring they rotate in perfect synchronization. 
• ECU Control: Engine sensors monitor the position of both the camshaft and crankshaft, providing data to the engine’s computer (ECU). 
• Harmonized Operation: The ECU uses this information to precisely time fuel injection and ignition, ensuring the engine runs efficiently and without issues.