What Is A Lifter On A Car?

Dustin Hawley | Dec 22, 2020

When researching vehicle engines, you may have heard about “lifters.” You might also have heard about them in the context of a repair, particularly if your engine is ticking.

So, what is a lifter, and what exactly does it do? Let’s take a closer look.

What is a car lifter

Car Lifter Basics

A lifter is a cylinder that sits between a car’s camshaft and the cylinder valves. As the camshaft moves over the top of the lifter, it actuates, temporarily opening the valve. And because the intake and exhaust valve need to open at different times, each has its own separate lifter.

Lifters can be designed differently, depending on the vehicle. For example, lifters on pushrod engines activate a rocker arm instead of directly pressing on the valve. 

That said, lifters fall into two types: hydraulic or mechanical. Let’s take a look at both.

Hydraulic Lifters

First invented in the 1930s to reduce the noise from older mechanical lifters, hydraulic lifters are the most common variety of lifter on the market. However, because of their higher cost, they didn’t enter the mass market until the 1950s.

Hydraulic lifters consist of a cylindrical body with an internal piston that protrudes from the top. Here’s how they work:

  • Pressurized oil enters through a hole in the lifter body and flows into a narrow channel. This oil enters the internal lifter cylinder but flows freely out the other side.
  • When the cam presses down on the lifter piston, it closes the channel. This locks the valve open temporarily, even under high pressure, so that gas can escape the cylinder.
  • When the cam passes its apex, the lifter piston can rise, allowing the oil to flow freely again. In turn, it causes the valve to snap shut, preserving proper engine air pressure.

The floating piston design aims to reduce valve lash, or the gap between the rocker arm and the valve tippet. Larger amounts of lash are more forgiving but can cause rattling and knocking. The less the lash, the quieter and smoother the ride.

A good set of hydraulic lifters will reduce valve lash to about 0.006 inches. That’s an incredibly tiny amount of space.

The problem here is that the lifter must operate to precise tolerances in order to do its job. If the engine RPMs are too high, the oil won’t have time to fully re-pressurize the valve, leading to reduced airflow and poor performance.

Conversely, a hydraulic lifter that becomes over-pressurized can fail to close the valves all the way. This will create leakage and can cause damage if the valve is too far open and prevents ignition.

Mechanical Lifters

Hydraulic lifters were in their heyday from the 1950s through the 1980s, when they were found in nearly every car on the road. However, some newer vehicles have started using mechanical lifters again.

They might be louder, but mechanical lifters have a couple of distinct advantages over their hydraulic counterparts. First, they’re cheap and low-maintenance, so they’re great for economy cars. They’re also useful for performance cars because they work reliably at higher RPMs.

There are two main types of mechanical lifters: solid lifters and roller lifters. A solid lifter is precisely what it sounds like: a solid metal cylinder. As the cam rotates, it either presses down on the cylinder or allows it to rise. 

Roller lifters have a similar design but are engineered to mitigate the noise from solid lifters. Instead of a flat back, they have rollers on the back that allow the cam to rotate smoothly over the top.

This significantly reduces noise and improves performance, particularly at higher RPMs. On the other hand, the rollers are higher maintenance than an ordinary solid lifter, leading to higher mechanic bills in the long run.

Lifters In Variable-Displacement Engines

We’ve already gone over some of the main developments in engine technology and what they mean, but variable-displacement engines present a unique challenge.

Variable-displacement engines go by various names, including “cylinder deactivation” and “displacement on demand.” Regardless of what it’s called, it’s the same basic technology: some of the engine’s cylinders are only used when they’re needed. Otherwise, they remain inactive.

The concept of variable displacement is simple. By shutting off some cylinders when they’re not needed, the engine conserves fuel.

However, having the valves continue to open and close would somewhat defeat the purpose. Air would still get pumped through these cylinders, wasting energy with every stroke. To maximize fuel economy, the valves should remain closed whenever the cylinder is not in use.

There are several ways of achieving this. In some vehicles, the cam has different lobes for each cylinder so that the valves can be individually activated and deactivated.

In other vehicles, advanced hydraulic lifters are used. These lifters will collapse when the cylinder is deactivated, so the cam will not actuate them. This kind of lifter requires a secondary oil supply hole, which requires a more elaborate design.

All of these functions are controlled by the powertrain control module (PCM). The good news is that everything is automated, so you should theoretically never have to make any manual adjustments.

The bad news is that multiple sensors and solenoids are involved in this kind of hydraulic lifter system. As a result, as with many electronic systems, it can be tough to troubleshoot when something fails.

Regardless of what method is used to deactivate unneeded valves, the effect is the same. Air becomes trapped in the cylinders and is compressed on the upstroke instead of being expelled through the valves.

On the downstroke, the air pressure helps propel the cylinder, returning most of the energy required to compress it. Less wasted energy translates to better gas mileage.

Summary

Lifters have been essential parts of the internal combustion engine for generations and will be for the foreseeable future. Want to learn more about your vehicle? Read our other informational articles! There’s a lot to learn, with new guides being published regularly.

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