Hydraulic Roller Camshaft Guide: What is it & Advantage

What is a Hydraulic Roller Camshaft

The hydraulic roller camshaft combines a rolling lifter and hydraulic mechanism into one unit, providing benefits that range from quiet operation to automatic lash adjustments. This guide will help you understand what these cams are, what they look like, and their advantages over solid types. So, let’s dive right in.

What is a Hydraulic Roller Camshaft?

It’s a type of camshaft designed to work with hydraulically operated roller lifters. The rollers slide on the cam lobes instead of wiping them, which reduces noise and friction for better engine performance and durability.

The hydraulic mechanism is an oil pressure-operated plunger that helps maintain a zero lash of the valve train; it automatically adjusts the lifter to make up for wear and thermal expansion of various components.


These cams are available as OEM or aftermarket types, also called retro-fits. Your choice depends on the performance requirements; plenty of options exist for regular street driving and moderately aggressive race applications.

Hydraulically operated roller lifters on an IC engine
Hydraulically operated roller lifters on an IC engine
Resource: https://www.youtube.com/watch?OK2lXecwcx4

How Does a Hydraulic Roller Camshaft Work?

The lifter of a hydraulic roller tappet cam has two crucial mechanisms: one, the wheel-like roller on one end of the assembly, and two, the hydraulically operated plunger that moves up and down under the action of pressurized engine oil. Here is what happens:

As the camshaft spins, a pushrod presses against the lifter, compressing the plunger. Oil enters the lifter via an opening on its body and into the plunger.

This oil will push against the plunger to effectively gap up and maintain the valve lash when the pressure exceeds that of the valvetrain components.

At the plunger bottom, a one-way valve prevents the oil from escaping until the clearance is gone. This action helps ensure zero valve lash or clearance. The plunger then remains under pressure from the engine oil’s pumping system.

Conversely, the wheels ride on the lobes. This motion allows the cam profiles to operate valve opening and closing components, such as pushrods and rockers. These actions describe the working of a typical hydraulic camshaft.

Hydraulic roller camshaft and lifters
Hydraulic roller camshaft and lifters
Resource: https://www.corvetteforum.com

Hydraulic Roller Camshaft Advantages and Disadvantages

Hydraulic cams came around a few decades ago to replace solid, flat tappets. Their mechanism offered several advantages, including reduced friction and quieter operation. They also eliminated the need to set valve train clearance periodically. However, they also had shortcomings, which we will find out below.

Advantages

  • Reduced Friction: The rolling wheel effortlessly moves over the lobe surface. That reduces friction considerably, minimizing the wear and providing for durability.
  • Self-Adjustment: You only need to give the required preload adjustment. Later, it adjusts itself automatically using the integrated oil mechanism.
  • Quiet operation: the roller cam produces less noise with minimal friction between it and the lifters, making them a preferred version for quiet, non-aggressive driving.
  • Increased Power: They allow a higher lift, increasing the amount of valve opening and duration. This action has proved to increase engine power.
  • No Break-In Needed: you do not need to break in a hydraulic camshaft. Breaking in camshafts is one of the reasons for early failure. That means reduced chances of damage when using them.

Disadvantages

  • Cost: hydraulically operated cams will cost you more; they are typically made from a more expensive material (billet steel) and feature complex construction involving rollers and hydraulics.
  • Weight: they’re also relatively heavy, which can take a toll on the need for high RPM horsepower.
  • Heavy-Duty Springs and Pushrods: with these cams, valve spring pressure can be pretty high, so the valves must use heavy-duty springs.
  • Limited Ramp rates and RPM: they do not support high revs. If you turn your engine above 6800, the hydraulic cam may not be a good idea.
Solid vs. hydraulic lifters
Solid vs. hydraulic lifters
Resource: https://www.youtube.com/watch?v=2GXVQI7TKVE

Solid Roller Cam vs. Hydraulic Roller Cam

There are typically two types of roller camshafts when grouped by the types of lifters they use: solid and hydraulic. Their comparison can help you make an informed decision, especially if torn between using either type. Let’s see how the two differ in construction, working, performance, and durability.

Construction

The primary difference between solid and oil-operated lifters is using a plunger assembly. The solid type does not use one. Instead, they’re simple on-piece components with only the wheel-like part on one end.

That makes roller types more expensive (as much as double or triple the price of solid cams). Note that if you’re buying an aftermarket roller cam, cast iron distributor gear will usually be pressed on its one end for use with the stock distributor gear.

Working

A hydraulic camshaft has the lifter move the plunger to maintain zero clearance, and the plunger is oil-operated. The solid type doesn’t and requires periodic adjustments. That makes them more demanding to maintain than the hydraulic styles.

The hydraulic types also allow higher spring pressures than the solid types. However, the solid types have steeper lobes, and the valves can open and close more quickly and aggressively, allowing faster ramp rates.

Performance

Hydraulic tappets and their cams offer better performance in some applications. Because of the automated lash adjustment, they’re less likely to fail due to clearance issues. Mechanical or solid types, on the other hand, accelerate faster but at the expense of wearing valve train components.

You can use roller cams with oil-operated lifters in various situations. They typically suit regular cars or those with mildly-modified engines. Mechanical or solid roller cams are available for moderate street driving and race engines.

While you can always choose a hydraulically operated mechanism for your engine cam lifters, it’s good to understand their limitations, such as RPM range and price range.

Hydraulic tappet roller lifter
Hydraulic tappet roller lifter
Resource: https://www.youtube.com/watch?v=Pnxs-X-W6tY

Can You Use Hydraulic Roller Lifters on a Solid Cam?

You could. However, each cam type has specific design differences that can make it less accommodating when used with a different lifter. For example, solid lifter cams have steeper profiles, while those meant for oil-operated lifters are milder.

It would help to have some valve clearance when running the hydraulic lifters on a solid cam. It serves to reduce the higher lift. Such lifters would work well if the cam has a less aggressive lobe profile.

Generally, it’s more appropriate to use a lifter with the kind of shaft the manufacturer designed it for (a solid with a solid shaft and the same case with oil-operated types).

That said, turning a small block engine with flat tappet cams into a roller type is possible. You only need a conversion kit.

Many auto parts manufacturers make hydraulic roller cams and lifter kits to allow engine builders to do that. The kits have the shaft and the lifters in their appropriate sizes, and no modifications are needed.

Conclusion

A hydraulic roller camshaft uses a wheel-like roller with a piston to adjust lash and maintain valve clearance while reducing friction and wear. These cam types offer several advantages, including reduced maintenance and durability.

WanTuo manufactures all types of camshafts, including solid and hydraulic roller camshafts. Whether you are looking for street, racing, or off-road cams, we have a range of choices. All our cams are manufactured in highly controlled conditions, ensuring their quality and reliability.

Louis
Louis

I'm Louis, a seasoned writer specializing in auto parts, particularly the science behind components like cylinder heads and pistons. With over a decade of experience and a background in mechanical engineering, my articles reflect a commitment to professionalism, blending technical insight with engaging content.

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