Stroking A 383 Engine: Achieving The Impossible 489 Dream?

Stroking an engine involves increasing the length of its stroke, which is the distance travelled by the piston from the top to the bottom of the cylinder. It is possible to stroke a 383 engine to a 489, with some claiming that it can result in a nice 500-horsepower engine that is still fairly streetable. However, others have raised concerns about the longevity of the pistons due to their short length. It is also worth noting that increasing the stroke of an engine does not necessarily increase its horsepower, but it can lead to more torque.

Stroker cranks and cast cranks

Stroker Cranks

Stroker cranks are a type of crankshaft that has gained popularity in recent years. They are characterised by their longer stroke, which increases the engine's displacement, resulting in higher torque and horsepower. Stroker cranks are commonly used in high-performance and racing engines to achieve greater power output. When choosing a stroker crank, it is important to select one that is rated for the intended level of power and type of driving. Additionally, matching the pistons and rods to the stroker crank is crucial to ensure compatibility and optimal performance. Stroker cranks are available for various engine types, including small block and big block engines.

Cast Cranks

Cast cranks, also known as cast steel crankshafts, are typically used in street engines with power outputs ranging from 300 to over 2000 horsepower. They are commonly available for domestic V8 engines and are designed to meet the requirements of most engine builds. Cast cranks are usually less expensive than stroker cranks and are suitable for stock rebuilds. They are made from cast steel and offer a cost-effective solution for engine builds. Cast cranks can be found in various vehicles, including Chevy, Ford, Dodge, and Plymouth models.

When choosing between a stroker crank and a cast crank, it is important to consider the specific requirements of your engine build. Stroker cranks offer increased performance, especially in high-power applications, while cast cranks provide a more economical option for street engines and stock rebuilds. It is crucial to select a crankshaft that matches the intended use, power output, and performance goals of your vehicle.

Compression ratios

When stroking a 383 to a 489, the compression ratio will be influenced by several factors. Firstly, the stroke increase from 3.75 inches to 4.25 inches in the 489 will have a significant impact on the compression ratio. A longer stroke means that the piston travels a greater distance, which affects the volume ratios in the cylinder. As a result, the compression ratio will increase.

However, it's important to note that the compression ratio can be fine-tuned by selecting the appropriate piston design. For example, pistons with a dish or a shorter compression height can help lower the compression ratio. This customization allows builders to tailor the engine's compression ratio to their specific requirements, such as the type of fuel used or the desired performance characteristics.

In addition to piston design, the choice of cylinder heads plays a role in determining the compression ratio. Different cylinder heads can have varying chamber volumes, which directly affect the compression ratio. By selecting cylinder heads with larger or smaller chambers, builders can adjust the compression ratio accordingly.

Lastly, the camshaft selection can also influence the compression ratio to some extent. Camshafts with different profiles can impact the engine's volumetric efficiency, which, in turn, affects the compression ratio. However, the camshaft's effect on compression ratios is not as significant as that of piston design and cylinder head selection.

When stroking a 383 to a 489, achieving the desired compression ratio requires careful consideration of these factors. Builders often aim for a specific compression ratio to match their intended use, such as high-performance applications or everyday street driving. By selecting the appropriate piston design, cylinder heads, and camshaft, they can fine-tune the compression ratio to optimize the engine's performance for their specific needs.

Camshafts

The camshaft's design features a series of eccentrics or lobes that interact with valve lifters or pushrods. These lobes, with their carefully designed protrusions, ensure that the valves open and close at the right times and for the right durations. This precise timing and duration of valve openings have a direct impact on the engine's performance, including power output, torque, and fuel efficiency.

There are two main types of camshafts: Flat Tappet and Roller Cams. Flat Tappet camshafts are commonly found in V8 engines, characterised by a flat-looking bottom where the cam lobe meets the tappet (lifter). Roller Cams, on the other hand, utilise a lifter with a roller, resulting in fatter lobes. Roller cams offer reduced friction, higher RPM potential, and the ability to handle higher valve spring pressures.

The shape and profile of the cam lobes play a crucial role in engine performance. The lobes' design includes the base circle (lowest point), the ramp (where the valve starts to open or close), and the nose (highest point when the valve is fully open). The lobe lift refers to the amount of lift generated at the lobe itself, while the valve lift is the resulting lift at the valve, multiplied by the rocker arm ratio.

Camshaft duration is another important concept, referring to the time it takes for a valve to open and then close completely. This duration is measured in degrees of crankshaft rotation. Increasing valve spring pressure on a flat tappet cam can lead to increased wear on the cam lobe and lifter, whereas roller cams can handle higher pressures, making them advantageous for building higher horsepower engines.

Pistons

In a four-stroke internal combustion engine, the piston performs four roles:

• As the piston goes down, it draws air and fuel into the cylinder or combustion chamber.
• On the upswing, it compresses the air and fuel in the cylinder so that it will ignite and explode.
• The spark plug ignites the air-fuel mixture, and the force flings the piston back down.
• The piston comes back to the top of the cylinder, expelling the burnt gases (exhaust) out of the cylinder.

In the context of stroking a 383 engine to a 489, piston choice is important. For instance, one user on a forum mentions using Ross pistons with a 9.92 dish. Another user mentions using forged Ross pistons with a 10.2:1 compression ratio.

Torque converters

The stall speed of a torque converter is a critical factor to consider. The stall speed refers to the rpm at which the torque converter fully engages and locks up. For a typical 383 stroker engine with a power output of around 400-500 horsepower and a camshaft operating range of 2500-5500 rpm, a stall speed between 2300-2500 rpm is often recommended for street use. However, it's important to note that this can vary depending on other factors, such as vehicle weight and gear ratio.

When choosing a torque converter, it is advisable to consult with multiple manufacturers and provide them with detailed information about your engine setup. This allows them to make informed recommendations tailored to your specific combination of parts. Some popular options for torque converters include B&M, Hughes Performance, Dynamic Converters, and Coan Racing. It is worth noting that some users have reported issues with B&M torque converters not fitting correctly on certain transmissions, so careful consideration and measurements are essential before making a purchase.

Additionally, it is important to strike a balance between torque and stall speed. While increasing the stall speed can provide benefits, it can also lead to higher transmission temperatures. Therefore, it is generally recommended to opt for a lower stall speed for street use to prevent overheating the transmission.

In conclusion, selecting the right torque converter for a 383 stroker engine requires careful consideration of various factors. Consulting with multiple manufacturers and providing them with detailed specifications of your engine setup will help ensure that you make an informed decision. Remember to take into account the stall speed, vehicle weight, gear ratio, and desired usage to achieve the desired performance and drivability.

Frequently asked questions