What Is a Stroker Engine?

Stroker engines are modified to increase the pistons’ throw. This results in the creation of more torque and greater engine power.
Written by John Davis
Reviewed by Melanie Reiff
background
A stroker engine is a motor that's had its crankshaft replaced or modified to increase the pistons' stroke or throw—the distance the pistons travel up and down in the cylinder. This results in more air and fuel forced into the combustion chamber, which, in turn, results in greater power and torque output, and a larger engine displacement.
Turbocharged four-cylinder engines and electric motors are largely replacing the beefy big blocks and muscle cars of yesteryear. But that doesn't mean there isn't still a thriving community of enthusiasts looking to squeeze every bit of power from their rides. A stroker kit is a significant aftermarket modification you can add to your engine to increase its torque and displacement—just be sure you know what you're doing before you start modifying your motor.
If you're thinking about installing a stroker kit on your engine or are just curious about what they are, you're in the right place. As a
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What is a stroker engine?

A stroker engine has been modified to have a longer stroke
But what exactly does that mean? Before we go into further detail about stroker engines, it might be helpful first to explain a little bit about how car motors work. 
Internal combustion engines get their power from explosions of fuel and air. This fuel/air combination is compressed into the combustion chamber by pistons moving up and down in the engine's cylinders. The crankshaft controls the pistons.
When the crankshaft has a longer stroke or throw—the distance it moves the piston down into the cylinder—the pistons can force a greater volume of air and fuel into the combustion chamber. When you increase the stroke, you generate more torque, the rotational force that allows your car to gain speed from a standstill faster. 

Types of stroker engines

There are a few different ways to stroke an engine. The first method is to increase the height of the engine block deck—the cavity that houses the pistons. You can do this by purchasing an aftermarket block deck that's customized for your engine. 
The second way to stroke an engine is to increase the length of the connecting rods, which allows the piston to travel further into the cylinder. However, this can cause the piston to collide with the cylinder head. If you increase the connecting rod length, you'll most likely need to purchase special pistons to accommodate the longer rods.
The third and easiest way to stroke an engine is to purchase a stroker kit. Stroker kits contain all the necessary parts to increase your motor's piston stroke and are specifically customized to fit your car's make and model. 
MORE: How to modify a car

Fitting a stroker kit

If you're planning to modify your car with a stroker engine, you must ensure that you purchase the correct parts for your vehicle. A stroker kit designed specifically for your car's engine is an excellent way to guarantee that you're getting the proper pieces of equipment.
Many stores that sell stroker kits will even help you assemble or install them on your car. When you purchase a stroker kit, you can expect it to come with a new crankshaft, I-beam or H-beam connecting rods, pistons, piston pins and rings, main bearings, and rod bearings
While stroker kits make this modification slightly easier than purchasing or machining individual parts, stroking an engine is still a complex job. It requires the disassembly of a large portion of the engine. And, unless you are an experienced mechanic, you are probably better off taking your car to a professional engine builder and letting them install the kit. 
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How does a stroker kit increase horsepower?

Stroker kits increase horsepower by increasing the engine displacement. When you stroke your engine and increase the stroke ratio, you're making it bigger. And larger engines will almost always generate more power. 

Pros of stroker engines

Stroker engines are a great way to increase your vehicle's power, especially if you're interested in drag racing or other extreme motorsports. Here are the upsides of stroked engines:
  • Greater engine displacement.
    Engine displacement
    is the volume occupied by the pistons in your engine's cylinders. It is measured in cubic inches and determined based on the cylinder bore size, the piston stroke, and the number of cylinders. Stroking the engine increases the piston stroke, resulting in a larger displacement and more torque.
  • Faster acceleration. More torque, along with a stroked crankshaft, allows you to reach higher speeds in a shorter period of time. 
  • Less downshifting. The increased torque from a stroker engine allows racers with manual transmissions to downshift less when cornering and performing tight maneuvers. 
  • Beefy internal engine components. Stroking your engine will likely reinforce the internals with more robust parts. 
MORE: 10 affordable American muscle cars

Cons of stroker engines

Stroker engines aren't without their drawbacks. Here are a few of the downsides to stroker engines:
  • Increased piston wear. Stroking an engine increases the piston travel, but not the time it takes for the piston to move that distance. This results in faster piston speed, which, over time, can damage the pistons and, potentially, the cylinder walls. 
  • Decreased performance at high RPMs. Greater torque doesn't come free of consequences. At higher RPMs, this power can become less stable. It can also cause tires to spin, leading to more drifting and tire wear. 
  • Engine mods can be dangerous. While most stroker kits are designed to fit specific engines with no problems, you're taking a risk any time you modify a motor. The manufacturer built your car to perform well in its stock condition. If you install the parts incorrectly or purchase the wrong components, there's a chance you could damage your vehicle.
  • Expensive. Engine building, even with a stroker kit, is costly. Depending on your goals, the cost to modify your motor may not be worth the power gains. 

What is torque versus horsepower?

So, stroker engines increase torque. But what is torque, and what's the difference between torque and horsepower?
Torque is a rotational force acting at a distance and is measured in pound-feet
Imagine you are trying to remove a bolt from your car. If you use a one-foot wrench and weigh 150 lbs, you're applying 150 lb-ft of torque to the bolt. If you can't get the bolt off and switch to a two-foot breaker bar, you're now applying 300 lb-ft of torque to the bolt (2 X 150 = 300). 
Horsepower refers to how fast you can perform work and is calculated by multiplying torque and RPM. Horsepower = torque X RPM / 5,252. For racecars and other performance vehicles, horsepower is typically measured on a special machine known as a dyno. 
So, if you're removing a bolt with your one-foot wrench and turning it 50 times per minute, you're effectively making 1.4 horsepower. 
In other words, horsepower is the total power output your engine is capable of making, while torque is the rotational power inside the engine and the force you feel that puts you in your seat when accelerating. 
Key Takeaway Torque is the rotational force that puts you in your seat when accelerating, while horsepower is the total power output your car can make.
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What is destroking an engine?

Destroking an engine is basically the reverse of stroking an engine. It involves shortening the pistons' throw by installing a crankshaft with a shorter stroke. This results in greater RPMs as the pistons must move faster to cover the same distance. 
Shorter stroke lengths generate more horsepower but at the expense of torque. The most common reason you might choose to destroke your engine is to fit into a smaller displacement category for races. 

Should you get a stroker kit?

Stroker kits aren't for everyone. You might be better off with a turbo or supercharger, depending on your goals. However, if you drive an older muscle car or are into drag racing, a stroker kit might be a good option for you. Stroker kits are an excellent mod for drivers of classic American muscle cars like Fords and Chevys. 
In fact, using a stroker kit, you can fit nearly 430 cubic inches into the classic Ford 351 Windsor. That's big block power coming from a small block without the extra size and weight. 
Stroker kits are ideal for modifying small block engines and increasing torque—a key component for drag racers. However, if you drive a sports car with a smaller, four-cylinder engine—like a
Nissan
or
Toyota
—you might be better off with a more modern mod, like a turbocharger. 
Further, if your driving goals include long-range travel or endurance racing, you might not need to increase your torque since you'll most likely keep your engine at a higher RPM. 

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Whether you drive a souped-up racecar with a stroker engine or a clean-running hybrid, you'll need a quality
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FAQs

Stroker motors increase the stroke or rod ratio. This results in an increased compression ratio and greater torque.
A stroker engine has a longer stroke—the distance the piston moves inside the cylinder—than a stock engine. You can achieve this result by replacing the crankshaft, connecting rods, or engine block deck.
Stroker engines can be expensive to build and maintain. Further, any time you modify your vehicle, you risk damaging the components or incorrectly installing the new parts.
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