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Engine Valvetrains 101

Brad Nelson
Diagram of a valvetrain.

The valvetrain plays a crucial role in your engine. It is the conductor orchestrating the precise opening and closing of engine valves, ensuring optimal airflow in and out of the combustion chamber. Far from the limelight of turbochargers and high-performance fuel systems, the valvetrain is the backbone of engine functionality, significantly influencing performance, efficiency and reliability.

What is it and How Does it Work?

The valvetrain is a collection of components responsible for managing the timing of the engine’s intake and exhaust valves. Its primary function is allowing fresh air to enter the combustion chamber and expelling exhaust gases. This coordination is crucial as it dictates how effectively an engine can breathe, impacting power output and fuel efficiency.

At the heart of this operation is the camshaft, which controls valve movement through a series of lobes that push against other components to open and close the valves as it spins. The camshaft is synchronized with the crankshaft, ensuring that valve operation is perfectly timed with piston movement.

Valvetrain Components

The valvetrain is composed of several interrelated components, each performing a specific function.

Camshaft

The camshaft is a rotating shaft equipped with cam lobes shaped to control valve timing and lift. It is driven by the crankshaft, usually through a timing chain or belt. In overhead camshaft designs, the camshaft is positioned above the valves, directly actuating them without the need for pushrods. In pushrod engines the camshaft is located below the valves.

Pushrods

Pushrods are necessary in engines where the camshaft is in the block rather than the cylinder head. They are slender, metal rods that transfer motion from the camshaft to the rocker arms in overhead valve engines. It’s like a chain reaction: camshaft lobes lift the pushrods and pushrods lift the rocker arms. Much like a teeter-totter, when the rocker arms are lifted on one side, the other end pushes down against the valve springs to open the valves. We dive deeper into each component within this system below.

Rocker Arms

Acting as levers, rocker arms translate the linear motion of pushrods into the vertical movement needed to open the valves. Their configuration can affect valve lift and timing, influencing engine performance.

Rocker Shafts

Providing pivotal support, rocker shafts allow rocker arms to pivot smoothly as they actuate the valves.

Valve Bridges

In engines with multiple valves per cylinder, valve bridges connect paired valves, ensuring they open and close in unison for optimal airflow.

Valves

The intake and exhaust valves control the flow of air and fuel into and out of the combustion chamber. Their precise operation is critical for maintaining engine efficiency and performance.

Valve Springs

These springs ensure that valves close completely after opening, maintaining the pressure needed to keep them seated against the valve seat.

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Timing Belt

The timing belt connects the camshaft and crankshaft to ensure synchronized rotation, critical for maintaining valve timing.

Belt Tensioner

This device maintains the proper tension on the timing belt, preventing slippage and guaranteeing precise valve timing.

Common Issues

The top end of the cylinder that includes the valve interface with the combustion chamber often lacks lubrication due to the limitations of the oil-control rings and combustion heat at the top of the cylinders. It’s also prone to the development of deposits and highly susceptible to corrosion, an issue compounded by the prevalence of water-absorbing ethanol in fuel. This can lead to increased friction and wear, affecting performance, and compound issues such as carbon buildup, which can impede valve operation.

Valve float occurs when the valve springs fail to keep up with the camshaft at high rpm, leading to incomplete valve closure. This can cause a loss of power and efficiency, and in severe cases, engine damage.

Protecting Your Valvetrain

Protecting your valvetrain is essential for engine performance and longevity. AMSOIL offers a range of products to help protect your valvetrain, helping reduce wear, extend component life and maximize performance.

Advanced Motor Oil

AMSOIL 100% synthetic motor oils provide excellent protection and thermal stability, reducing wear and extending component life. AMSOIL Signature Series 100% Synthetic Motor Oil provides 75% more protection against horsepower loss and wear.1

Powerful Fuel Additives

AMSOIL offers a duo of powerful additives to help protect your valvetrain: AMSOIL P.i.® Performance Improver and AMSOIL Upper Cylinder Lubricant.

Treating your engine with AMSOIL P.i. every 4,000 miles (6,437 km) can help your engine maintain horsepower and performance.

AMSOIL P.i.

AMSOIL P.i. attacks carbon and sludge buildup head-on with concentrated detergents that aggressively clean stubborn, power-robbing deposits from injectors, valves and the combustion chamber. Independent testing demonstrated the performance of P.i. using a 2016 Chevrolet* Silverado* with 100,616 miles (161,926 km) on the odometer. Following a single treatment with P.i., the truck measured a 14% improvement in horsepower.2

P.i. restores GDI fuel injectors to 100% flow rate after one tank of fuel.3 It helps keep valves clean and moving freely; helps protect against compression loss, difficult starting and rough idling; improves fuel economy and helps restore power and performance.

Upper Cylinder Lubricant

AMSOIL Upper Cylinder Lubricant helps preserve and build on the gains made by AMSOIL P.i. It lubricates the top end of the engine, fights ethanol-related corrosion and maintains cleanliness, particularly in the all-important fuel injectors.

Upper Cylinder Lubricant deploys unique additives to provide essential lubrication and reduce piston-ring and cylinder wear – maximizing engine compression and horsepower. Its lubricity improvers also aid in protecting fuel injectors and other fuel-system components from wear. AMSOIL Upper Cylinder Lubricant delivers 18% more lubricity than Lucas* and 20% more than Sea Foam* for better retention of horsepower and fuel economy.4

To battle corrosion, Upper Cylinder Lubricant uses potent corrosion inhibitors that coat metal surfaces, block out moisture and stop deterioration before it starts. This is particularly important when using gasoline that contains water-absorbing ethanol.

AMSOIL Engine and Transmission Flush

If you suspect or know that your engine has a maintenance history that includes lower-quality motor oil, AMSOIL Engine and Transmission Flush can help clean and restore it. Its potent, detergent-based formula cleans sludge and deposits from your engine, including the upper regions, to help loosen sticky valves and rings and remove harmful sludge and deposits. AMSOIL Engine and Transmission Flush helps restore fuel economy, improve performance and promote longevity. It’s safe on parts and can be easily disposed of with waste oil.

Component Checks

Monitoring the timing belt and tensioner is vital. Replace the timing belt as specified in your owner’s manual and check the tensioner for wear to avoid slippage or failure.

Regularly inspect valve lash, the clearance between the rocker arm and valve stem, to ensure it remains within specification. Incorrect valve lash can lead to noise, inefficiency and even damage.

Valve springs should be checked for signs of weakness or breakage, as these can lead to valve float. Replacing old or worn springs with new, high-performance options can enhance engine reliability, especially in high-rpm applications.

Long Live the Valvetrain

The valvetrain is a vital and intricate system that demands attention and care. Proper maintenance will help keep your engine’s valvetrain in excellent condition so you can enjoy maximum performance, improved fuel efficiency and long engine life.

 

1Based on independent testing of AMSOIL Signature Series 0W-20 using the ASTM D6891 standard test.

2Based on third-party testing in a 2016 Chevrolet* Silverado* 1500, 5.3L V-8 GDI with 100,616 miles, using one tank treated with AMSOIL P.i. Actual results may vary.

3ASTM D5598(M) – 2013 Buick Regal test vehicle.

4Based on independent testing of AMSOIL Upper Cylinder Lubricant, Lucas Upper Cylinder Lubricant and Sea Foam Motor Treatment obtained on 02/13/2019 using the ASTM D6079 modified for use with gasoline.