The small-block Chevy engine is an undeniable symbol of American engineering ingenuity, representing a powerful legacy that spans generations of automotive enthusiasts and industry professionals alike.
With a level of versatility that is simply unparalleled, this engine has proven itself time and time again in a wide variety of demanding applications, ranging from street performance to racing and everything in between.
At the core of this impressive power plant lies the cylinder head – a complex and critical component that serves as the gatekeeper of fuel and airflow, regulating and directing the lifeblood of the engine itself.
In this detailed post, we’ll dive deep into the intricate details of two of the most popular cylinder head options for small-block Chevy engines: the 862 heads and the 706 heads.
These heads stand as a testament to the enduring commitment to quality and performance that the small block Chevy engine represents, and we will be exploring every aspect of their specifications, performance, and cost in order to provide you with a truly comprehensive understanding of which option is the right choice for your specific engine needs.
Let’s dive right into it!
Table of Contents
862 Heads vs 706 – Specifications
862 Heads Specifications
Overview
The 862 LS heads have been a top pick among small-block Chevy engine enthusiasts for their high-performance capabilities at a reasonable cost.
One of the defining characteristics of these heads is their small combustion chamber volume, clocking in at around 64cc.
This small volume translates to a higher compression ratio, resulting in increased horsepower and torque output that can make all the difference on the road or track.
Chamber Volume and Shape
The shape of the combustion chamber in the 862 heads is just as important as its size. Unlike many other cylinder head options, the 862s feature a modified heart shape, which contributes to more efficient air and fuel flow.
The unique shape of the chamber helps to create a more controlled and evenly distributed flame front during combustion, which can improve fuel economy and make the engine run more smoothly overall.
Valve Size
When it comes to the valves, the 862 heads don’t disappoint either. They come equipped with larger intake and exhaust valves than previous small-block Chevy cylinder head options.
The intake valves measure a sizable 1.94 inches, while the exhaust valves measure at 1.50 inches. These larger valves provide a significant increase in airflow, allowing more fuel and air to enter the combustion chamber and produce even more power.
Intake Port Size
In addition to larger valves, the 862 heads have a larger intake port than previous small-block Chevy cylinder head options.
The port measures at around 165cc, which helps to increase airflow even further and unlock even more potential for power gains.
However, it’s worth noting that using the 862 heads may require some modification to the intake manifold to achieve optimal performance.
All in all, the 862-cylinder heads are a top choice for anyone looking to boost the performance of their small-block Chevy engine without breaking the bank.
With their small combustion chamber volume, unique chamber shape, and larger valves and intake port, the 862s have all the features needed to provide excellent performance gains for a wide range of applications.
706 Heads Specifications
Overview
The 706 heads are a popular choice for small-block Chevy engines and were first introduced back in 1999. They were used in various engines until 2007 and remain a viable option for those seeking a cylinder head upgrade.
Compared to the 862 heads, the 706 heads have a larger combustion chamber volume, measuring around 71cc.
This difference in size results in a lower compression ratio, which can be advantageous for engines running on lower-octane fuel or utilizing forced induction.
Chamber Volume and Shape
Unlike the modified heart shape of the 862 heads, the 706 heads have a more conventional, rounded chamber shape. This can affect airflow and combustion efficiency, but it can also make it easier to find compatible parts and accessories.
However, it’s important to note that the combustion chamber shape can have a significant impact on engine performance.
Valve Size
The valve size of the 706 heads is similar to the 862 heads, with an intake valve size of 1.94 inches and an exhaust valve size of 1.50 inches.
This valve size provides improved flow and greater efficiency, allowing more air and fuel to enter the combustion chamber.
Intake Port Size
The larger intake port size of the 706 heads, measuring around 170cc, also allows for greater airflow and increased performance potential.
However, as with the 862 heads, modifications to the intake manifold may be necessary for optimal performance.
Comparison of 862 and 706 Heads Specifications
| Specifications | 862 Head | 706 Head |
| Combustion Chamber Volume (cc) | 64 | 71 |
| Chamber Shape | Modified Heart | Rounded |
| Intake Valve Size (Inches) | 1.94 | 1.94 |
| Exhaust Valve Size (Inches) | 1.50 | 1.50 |
| Intake Port Size (cc) | 165 | 170 |
Pros and Cons of 862 Heads and 706 Heads
Pros of 862 Heads
The following are some of the advantages you’ll need to consider while making a decision on which cylinder head to go for:
1. Small Combustion Chamber Volume
The 862-cylinder head’s small combustion chamber volume of around 64cc allows for a higher compression ratio, resulting in greater horsepower and torque output.
2. Improved Fuel and Air Flow
The modified heart shape of the 862 head’s combustion chamber allows for improved fuel and air flow.
3. Larger Valves
The 862 heads have larger intake and exhaust valves than previous cylinder head options, providing improved flow and greater efficiency.
4. Larger Intake Port
862 head’s larger intake port size of around 165cc allows for greater airflow and increased performance potential.
Cons of The 862 Head
1. Modifications Required
The 862 heads may require modifications to the intake manifold in order to achieve optimal performance.
2. Cost
While the 862 heads are considered an affordable option for small-block Chevy engines, they may still be more expensive than other options on the market.
3. Not Ideal for All Applications
The high compression ratio of the 862 head may not be suitable for all applications, and the modifications required may make them less practical for some engine builds.
862 Heads vs 706 – Performance Comparison
| Performance Characteristics | 862 Head | 706 Head |
| Compression Ratio | Higher | Lower |
| Performance Potential | Higher | Lower |
| Airflow | Improved | Improved |
862 Heads vs 706 – Applications
Street Performance
Street Performance of The 862 Head
The 862 heads have been a popular choice for street performance for a while now, and it’s no surprise why. Their relatively small combustion chamber size and efficient airflow make them a desirable option for those seeking improved power and torque.
With a combustion chamber volume of approximately 64cc, the 862 heads can provide a higher compression ratio which results in better engine performance.
The intake and exhaust ports of the 862 heads have been engineered to optimize airflow and improve performance potential. They provide better fuel efficiency, lower emissions, and increased horsepower, making them an excellent choice for street use.
Street Performance of The 706 Head
It’s worth noting that the 706 heads have a larger combustion chamber than the 862 heads, which measures at around 71cc.
While this might sound like a disadvantage, it can actually be helpful for engines running on lower-octane fuel or those using forced induction.
While the 706 heads can offer good street performance gains, it’s important to consider your specific engine build and intended use.
Depending on your application, you may need to make modifications to the intake manifold and exhaust system to fully realize the performance potential of the 706 heads.
In addition, if you plan to use high levels of boost or nitrous oxide, additional modifications and careful tuning may be necessary to prevent engine damage.
Overall, the 706 heads can be a good choice for upgrading your car’s performance if you’re running on lower-octane fuel or using forced induction. With proper planning and modifications, you can achieve great street performance gains.
Drag Racing
Drag Racing Performance of the 862 Head
The 862 head is a popular choice among drag racing enthusiasts because of its exceptional airflow efficiency and small combustion chamber size.
These two attributes translate to higher compression ratios, and in turn, improved power and torque outputs. The carefully designed intake and exhaust ports of the 862 heads ensure that the airflow is optimized, which can significantly increase the horsepower and torque output.
In the high-stakes world of drag racing, every fraction of power and performance counts, and the 862 heads can deliver that extra edge.
However, it’s essential to understand that drag racing requires a significant level of engine modifications. As such, the 862 heads may need additional fine-tuning and modifications to fully realize their performance potential.
One of the benefits of the 862 heads for drag racing is their ability to generate higher compression ratios, which translate to increased power and torque.
Moreover, the smaller combustion chamber size can make it easier to calibrate the engine for optimal performance as it can provide better fuel efficiency and lower emissions.
However, each engine build is unique, and modifications to the intake manifold and exhaust system may be necessary to get the best out of the 862 heads.
Careful and meticulous tuning and monitoring are also crucial to prevent engine damage, especially when using nitrous oxide or other forced induction methods.
Drag Racing Performance of the 706 Head
The 706 head is another go-to choice for drag racing enthusiasts because it has an impressive intake port size of around 170cc, which allows for greater airflow and increased performance potential.
With a larger combustion chamber volume measuring around 71cc, the 706 head has a lower compression ratio, making it a great option for engines using forced induction or running on lower octane fuel.
When it comes to drag racing, every little advantage counts, and the 706 heads provide that extra edge. One of its significant advantages is that it’s compatible with forced induction or lower octane fuel, thanks to its lower compression ratio.
In addition, the larger intake port size can help improve airflow, which in turn can lead to increased horsepower and torque output.
However, keep in mind that every engine build is unique, and to optimize performance, modifications to the intake manifold and exhaust system may be required.
It’s also crucial to do careful tuning and monitoring to prevent engine damage in high-performance applications, particularly those using nitrous oxide or other forms of forced induction.
Road Racing
Road Racing Performance of The 862 Head
The 862 head is a popular choice for both drag and road racing applications, as it boasts an efficient airflow and a small combustion chamber size, which can provide higher compression ratios and improved power and torque.
The intake and exhaust ports of the 862 heads are specifically designed to optimize airflow, resulting in increased horsepower and torque output.
Road racing is all about performance and reliability, which are both provided by the 862 heads. The efficient airflow of the 862 heads can give drivers a competitive advantage on the track.
However, as with any high-performance engine build, it’s important to note that careful tuning and monitoring are necessary to prevent engine damage.
One of the benefits of the 862 heads in road racing is their ability to deliver higher compression ratios, which can lead to increased power and torque.
Moreover, the smaller combustion chamber size makes it easier to tune for optimal performance, offering better fuel efficiency and lower emissions.
Nonetheless, to achieve optimal performance, modifications to the intake manifold and exhaust system may be required in road racing applications.
Road Racing Performance of The 706 Head
The 706 head is a favored choice for those in the road racing world and for good reason. This bad boy boasts a larger intake port size of around 170cc, which allows for better airflow and the potential for even greater performance gains.
On top of that, the 706 head has a combustion chamber volume of roughly 71cc, resulting in a lower compression ratio that’s perfect for engines running on lower octane fuel or forced induction.
Road racing is no joke – it requires top-notch performance and reliability, which is exactly what you get with the 706 heads.
The larger intake port size can mean more horsepower and torque output, while the lower compression ratio helps improve engine reliability in high-performance road racing applications.
One of the main perks of the 706 heads is their versatility when it comes to forced induction or lower octane fuel, thanks to their lower compression ratio.
And don’t forget the larger intake port size, which improves airflow and can lead to even more horsepower and torque output.
Just keep in mind that some modifications to the intake manifold and exhaust system might be necessary to really optimize performance in road racing applications.
It’s all about careful planning and modifications, as well as consistent maintenance and monitoring if you want to get the most out of your 706 heads on the track.
862 Heads vs 706 – Cost
862 Head Cost
The cost of an 862 head can vary considerably depending on the specific manufacturer and retailer, with prices generally ranging from $400 – $600.
While at first glance it may seem like a hefty investment, it’s vital to take into account the potential performance enhancements that can be attained with the efficient airflow and small combustion chamber size of the 862 head.
When weighed against the cost of other high-performance parts, the cost of an 862 head can indeed be regarded as a good value for money, as it can generate significant increases in horsepower and torque output.
However, it’s imperative to note that attaining the full performance potential of the 862 head may require additional modifications to the engine and other parts.
Nevertheless, the cost of an 862 head is a worthwhile investment for those seeking to boost the performance of their engine for drag racing or road racing applications.
With careful planning and installation, it can offer exceptional value for its cost and provide a significant improvement in engine performance, ultimately leading to a more satisfying driving experience on the track.
706 Head
The cost of a 706 head can vary depending on several factors, including the manufacturer, retailer, and any additional modifications that may be necessary to optimize its performance. Generally, the price can range from $300 – $500.
While the cost may seem steep at first glance, it’s important to consider the potential gains in performance that can be achieved with the 706 head’s larger intake port size and lower compression ratio.
These features can significantly improve airflow and horsepower output, ultimately providing a better value for the money spent.
Compared to other performance parts, the cost of a 706 head can be considered reasonable, especially when the potential increase in performance is taken into account.
However, it’s important to keep in mind that additional modifications may be required to fully realize the benefits of the 706 head.
The cost of a 706 head can be a worthwhile investment if you’re looking to boost the performance of your engine in road racing or other high-performance applications.
Conclusion
After considering the various factors and characteristics of the 862 and 706 heads, it becomes clear that both have their advantages and disadvantages.
While the 862 head offers a larger combustion chamber and intake port, making it suitable for high horsepower and naturally aspirated engines, the 706 head’s smaller combustion chamber and increased airflow potential make it a better choice for forced induction applications.
However, cost is also an important factor to consider. The 706 head is generally more affordable than the 862 head, which may make it a more attractive option if you’re looking to improve your engine’s performance without breaking the bank.
In terms of value for money, both heads offer a good investment for those looking to increase the performance of their engine.
Ultimately, the choice between the 862 and 706 heads will depend on a variety of factors, including the specific engine, intended use, and budget.
It’s important to carefully consider these factors and consult with experts in the field to make the best decision for your individual needs.
Looking to the future, it’s likely that advances in technology and manufacturing will continue to improve the performance potential and cost-effectiveness of both the 862 and 706 heads, as well as other engine components.
Keeping an eye on these advancements and staying informed about the latest developments in the industry will be crucial if you’re looking to stay on the cutting edge of high-performance engine building.
