How a Camshaft Works in a V8

A camshaft in a V8 engine is a precisely machined shaft with lobes that opens and closes the 16 valves in sync with the pistons by rotating at half the crankshaft’s speed; it can sit in the block (pushrod/OHV) or in the heads (OHC), and modern versions often use variable valve timing to shift when valves open for better torque, power, and efficiency. In practice, the camshaft orchestrates airflow—deciding how much, how long, and when gases move—so the engine breathes correctly across thousands of rpm.

What the Camshaft Does

Every four-stroke V8 needs its intake and exhaust valves to open and close at exactly the right moments. The camshaft’s lobes—egg-shaped rises along the shaft—convert rotary motion into linear motion that lifts lifters/tappets, pushrods, and rocker arms (in OHV engines) or acts directly on followers/buckets (in OHC engines). This motion opens the valves against spring pressure; as the lobe rotates past its peak, the spring closes the valve. The cam’s geometry and timing determine breathing behavior, idle quality, torque curve, emissions, and the engine’s signature sound.

Core Components and Layouts

V8 engines use several camshaft architectures, each affecting packaging, weight, friction, and rpm capability. Below are the common layouts and how they transmit motion to the valves.

• OHV (pushrod) with a single cam-in-block: One camshaft below the heads drives 16 valves via lifters, pushrods, and rockers. Common in classic American V8s (Chevrolet small-block/LS/LT, Chrysler Hemi, many GM/Chrysler truck engines).
• SOHC/DOHC per bank: Overhead cams sit in the cylinder heads. Many modern V8s use DOHC (two cams per bank, four total) for high airflow and finer control (Ferrari, Mercedes-AMG, BMW, Lexus/Toyota, Ford Coyote is DOHC; Ford Modular V8s also came in SOHC/DOHC variants).
• Mixed drives: Chains are most common; belts exist in some V8s (notably certain Audi/Volkswagen-family V8s), sometimes combined with short secondary chains or gears to link cams on each bank.

Regardless of the layout, each valve needs a matched cam lobe, and the lobes are sequenced to the engine’s firing order so every cylinder gets the correct valve events at the correct crank angle.

How Timing Works in a Four-Stroke V8

The camshaft must synchronize valve motion with piston position through the four strokes, rotating at exactly half the crankshaft speed. Here’s how the cam interacts with each phase.

1. Intake stroke: Near the end of exhaust, intake valves begin to open (overlap). As the piston descends, intake valves open wide, allowing fresh charge to flow in, then begin closing after bottom-dead-center to use inertia for better cylinder fill.
2. Compression stroke: Both valves are closed so the rising piston compresses the mixture. Slight cam advance can close the intake earlier for low-rpm torque; later closing favors high-rpm power.
3. Power stroke: With both valves closed, combustion forces the piston down. Valve timing keeps them sealed to retain pressure.
4. Exhaust stroke: Exhaust valves open before bottom-dead-center of the power stroke to start blowdown. Near top-dead-center, intake begins to open (overlap) to scavenge exhaust and improve volumetric efficiency.

The fact the cam turns at half speed is critical: in a four-stroke, each cylinder fires every two crank revolutions, so valve events repeat every 720 crank degrees—mapped by the cam’s 360-degree rotation.

Synchronization and Phasing

How the Cam Is Driven

Keeping the cam and crank synchronized under heat, load, and wear is a mechanical challenge. Manufacturers use different drive systems depending on durability targets, NVH, packaging, and cost.

• Chains: Most common in modern V8s; robust and compact. May use guides, tensioners, and multiple chains (primary and secondary) in DOHC designs.
• Belts: Quieter and lighter; used less often in V8s but present in some applications. Usually scheduled replacement items.
• Gears: Extremely precise and durable, often in racing or heavy-duty engines, but noisier and heavier.

Any slack or stretch alters cam timing. Modern engines use tensioners (often oil-fed) and precise phasers to maintain accuracy across operating conditions.

Variable Valve Timing and Lift

Many current V8s employ cam phasers that rotate the cam(s) a few degrees relative to the crank—using oil pressure or electric actuators—to advance or retard events. Some add variable lift systems or multi-step rockers to change how far valves open, and cylinder deactivation systems that collapse special lifters to keep certain valves closed under light load. These strategies broaden torque, reduce fuel use, and cut emissions without sacrificing peak output.

These are the typical effects manufacturers target with variable valve timing and lift on V8s.

• Earlier intake closing at low rpm to improve torque and drivability.
• Later intake events and more overlap at high rpm to boost top-end power.
• Stable idle and reduced pumping losses for better fuel economy.
• Lower emissions during warm-up and part-throttle operation.

The end result is a wider, flatter powerband and improved efficiency, with software seamlessly blending modes moment by moment.

Firing Order, Crank Type, and Sound

V8s typically use a 90-degree bank angle and either a cross-plane or flat-plane crankshaft. Cross-plane cranks (common in American V8s) yield uneven exhaust pulse spacing per bank and that deep, burbling sound; flat-plane cranks (used by Ferrari and some high-revving performance V8s) alternate evenly and rev faster with a sharper note. The camshaft’s lobe sequence must match the engine’s firing order and bank arrangement so each cylinder’s intake and exhaust events align with its firing TDC. Overlap and lobe separation angle also shape the exhaust note—tight separation and long duration produce the classic “lope” at idle.

Performance Terms That Matter

Camshaft specs explain how a V8 will behave. These are the key parameters enthusiasts and engineers watch.

• Lift: Maximum valve opening height. More lift generally increases flow but stresses springs and valvetrain.
• Duration: Crankshaft degrees a valve is held open (often quoted at 0.050-inch lift in imperial specs). Longer duration favors high rpm but can hurt low-speed torque and idle.
• Lobe Separation Angle (LSA): Degrees between intake and exhaust lobe centerlines on a cylinder. Tight LSA increases overlap (lumpier idle, stronger midrange), wide LSA smooths idle and widens the torque curve.
• Centerline/Advance: Where peak lift occurs relative to TDC. Advancing intake improves low-end; retarding can help top-end.
• Overlap: Degrees both valves are open near TDC between exhaust and intake. Helps scavenging at high rpm; can dilute idle.
• Ramp Rates: How quickly the valve accelerates. Faster ramps increase area under the curve but stress components.

The “right” cam is a compromise among drivability, emissions, longevity, and the engine’s intended rpm range, gearing, and vehicle weight.

Reliability, Wear, and Maintenance

Because the cam controls all valve motion, its health is critical. Modern oils, materials, and designs have improved lifespans, but several points still matter for V8 owners and builders.

• Lubrication: Flat-tappet cams are sensitive to oil chemistry; adequate ZDDP during break-in is essential. Roller lifters reduce sliding friction and wear.
• Timing Components: Chains, guides, and tensioners wear; belts are service items. Noise on start-up or cam/crank correlation codes can indicate issues.
• Phasers and Solenoids: Oil-quality dependent; varnish or low pressure can cause timing jitter, rough idle, or loss of performance.
• Valve Lash: Hydraulic lifters auto-adjust; solid/shim systems need periodic checks to maintain precise timing and prevent damage.
• Cylinder Deactivation Lifters: In some V8s, failed deactivation lifters can collapse or stick, causing misfires and valvetrain noise.
• Break-In and Springs: Stiffer springs increase performance headroom but raise wear; correct break-in procedures and matched components are vital.

Attentive maintenance—quality oil, timely timing-component service, and clean operation—preserves cam timing accuracy and valvetrain health, protecting power and efficiency.

Summary

In a V8, the camshaft is the mechanical conductor that times airflow to each cylinder, spinning at half the crank’s speed to open and close 16 valves with precision. Whether it lives in the block (OHV) or the heads (OHC), its lobe design and timing dictate how the engine breathes, sounds, and performs. Modern phasers and variable lift expand the usable powerband and improve economy, while correct specs, maintenance, and synchronization keep the engine smooth, strong, and reliable.

How does a camshaft work in an engine?

Camshafts are integral components of internal combustion engines, responsible for controlling the opening and closing of the engine’s intake and exhaust valves. As the camshaft rotates, its lobes push against the valves, allowing the intake of air and fuel and the expulsion of exhaust gases.

What does a cam do to a V8 engine?

The camshaft activates a cylinder’s intake and exhaust valves. One lobe will activate the intake valve, followed by a second lobe that activates the exhaust valve. As the shaft rotates, the valves will open and close in the appropriate timing.

What are the downsides of a Cammed engine?

In our own demo car we picked up 100 wheel horsepower going to a large cam but what that results in is a loss of fuel economy, and a loss of power and torque below around about 3000 RPM and you’re also going to get the car pushing a little bit when it’s in gear because the idle speed needs to be higher so there is a …

How does a cam increase horsepower?

A cam increases horsepower by changing valve lift, duration, and timing to allow more air into the combustion chamber and exhaust gases to escape faster, improving engine breathing and efficiency. Specifically, more lift opens the valves further, increasing the volume of the air-fuel mixture, while more duration keeps them open longer, providing more time for the cylinder to fill and scavenge. Modified timing can also optimize performance at higher engine speeds.
 
This video explains the process of how a camshaft increases horsepower: 57sTobyVegaDYouTube · Jun 15, 2022
How Camshafts Increase Horsepower

• Increased Valve Lift: Opens in new tabThe “lift” of a camshaft lobe dictates how far the intake and exhaust valves open. A performance camshaft is designed with more lift, allowing a greater volume of fresh air and fuel to enter the combustion chamber and spent gases to exit. 
• Increased Valve Duration: Opens in new tab”Duration” refers to the amount of time the valves remain open. A higher duration cam keeps the valves open for a longer period, providing a longer window for air to enter the cylinder and for exhaust gases to escape, which can improve peak horsepower at higher RPMs. 
• Optimized Valve Overlap: Opens in new tabA performance cam can also be designed to have “overlap,” where both the intake and exhaust valves are open simultaneously for a short period. This overlap can help to sweep exhaust gases out and draw in the fresh air-fuel charge more efficiently. 
• Improved Engine Breathing: Opens in new tabThe combined effects of increased lift and duration allow the engine to “breathe” more freely, as more air can be drawn in and more exhaust gases can be expelled from the cylinder in a given amount of time. 
• Higher RPM Power Band: Opens in new tabBy optimizing airflow at higher engine speeds, a performance cam allows the engine to generate more power at higher revolutions per minute (RPMs). 

You can watch this video to learn more about the benefits of a camshaft upgrade: 1mMotor MatchupsYouTube · Apr 28, 2024
Key Takeaway
A performance cam increases horsepower by more aggressively controlling valve timing and movement, resulting in increased airflow and a more efficient combustion cycle, particularly at higher engine speeds.