862 vs 706 Heads: Friendly Comparison to Find the Best

When it comes to choosing the right cylinder head for your car, you might find yourself in a dilemma between 862 and 706 heads.

Both 862 and 706 cylinder heads play a crucial role in the top of the combustion chamber, withstanding extremely high temperatures and immense pressure.

This article aims to provide insight into the differences between these two popular options, helping you to choose the right one for your car.

862 Vs 706 Heads - Which One Is Better

 

What are 862 and 706 Heads Known For?

The 862 heads are known for their lightweight, aluminum construction, offering better fuel economy and performance.

These heads are commonly used in high-performance vehicles and race cars, thanks to their efficient heat dissipation and weight-saving characteristics.

On the other hand, 706 heads are slightly preferred in some cases due to their semi-permanent mold (SPM) manufacturing process, which provides a more durable product.

Examining the key factors such as casting process differences, performance, efficiency, materials and manufacturing, as well as applications and market availability will help determine the ideal choice for your vehicle.

After comparing the benefits and drawbacks of each head and understanding the impact of modifications and upgrades, you can pick the one that suits your needs.

862 Heads Vs 706 Heads: A Brief Overview

Both 862 and 706 heads are popular choices for cylinder heads in engines.

862 Heads Vs 706 Head Comparison 

Feature862 Heads706 Heads
Casting ProcessSand-castSemi-permanent mold (SPM)
Combustion Chamber VolumeSmallerLarger
Valve SizeLarger valvesSmaller valves
Intake Port SizeLarger intake portSmaller intake port
BenefitsImproved fuel and air flowMore consistent process
DrawbacksModifications required, costSlightly lower efficiency

Comparing these two head types, it’s evident that:

  • 862 heads provide improved fuel and air flow, thanks to their larger valves and intake port size.
  • 706 heads, on the other hand, are made with a semi-permanent mold (SPM) method, which results in a more consistent process and construction.

However, there are a few drawbacks to consider as well:

  • 862 heads typically require modifications and can be more expensive due to the casting method and material used.
  • 706 heads might suffer from slightly lower efficiency due to their smaller valves and intake port size.

The choice between these two heads ultimately depends on your specific needs and goals for your engine. Consider the pros and cons of each before making a decision.

Casting Process Differences

Sand Casting

Sand casting is a method that uses sand molds for producing cylinder heads, such as the 862 and 706 heads. In this process:

  • A pattern is formed from the actual head
  • Sand is packed around the pattern to create the mold
  • Molten metal is poured into the sand mold to cast the cylinder head

Examples of sand cast cylinder heads include:

  • Casting number 862
  • Casting number 706

Semi-Permanent Molds

Semi-permanent molds are used for producing intricate and detailed components of the engine. The process involves:

  • Two or more sections tightly fitting together
  • Molten metal is poured into the mold cavity
  • The mold is dismantled after coolant solidifies

This method is favored for its precision and accuracy in casting intricate parts. However, it is not commonly used for cylinder heads like the 862 and 706.

Comparison Table

Method862 & 706 Heads UsageMaterialPrecision
Sand CastingApplicableSandModerate
Semi-Permanent MoldNot ApplicableMetal or Ceramic formsHigh

Therefore, sand casting is the technique used for manufacturing both 862 and 706 heads.

Semi-permanent mold casting is not applicable for these specific cylinder heads. While the sand casting is relatively less accurate, it is suitable for producing these heads and is cost-effective.

862 Vs 706 Heads - Which One Is Better

 

Compression Ratio and Combustion Chamber

862 heads and 706 heads both make up the top of the combustion chamber in engines. These cylinder heads need to withstand high temperatures and pressure.

  • 862 Heads: These heads have smaller valves of 1.89 intake, less than 2.00 valves, and a small combustion chamber that results in a better compression ratio. They are known for excellent flow and providing higher compression.
  • 706 Heads: These heads are quite similar to the 862 heads in appearance, with the main differences being in the compression ratio and the vehicles they are suitable for.
 862 Heads706 Heads
Compression RatioBetterLower
Combustion Chamber SizeSmallerLarger
Suitable VehiclesRange of applicationsMore limited applications

Both 862 and 706 heads contribute to the engine’s performance, but the former offers higher compression with its smaller combustion chamber.

Valves and Port Volumes

When comparing the 862 and 706 cylinder heads, it’s essential to examine their valves and port volumes. Both types come with two valves per cylinder: one intake valve and one exhaust valve.

For the 862 heads, the intake valve size is 1.89 inches and the exhaust valve measures 1.55 inches.

The 706 heads, however, feature an intake valve size of 2.00 inches and an exhaust valve size of 1.55 inches.

In terms of port volumes, the 706 heads have larger intake ports. Here’s a comparison table to illustrate the differences:

Cylinder HeadIntake Valve SizeExhaust Valve SizeIntake Port Volume
8621.89 inches1.55 inchesSmaller
7062.00 inches1.55 inchesLarger

The variations in valve sizes and port volumes impact the flow properties of both cylinder head types. With the larger intake valves and intake port volume, the 706 heads tend to provide better flow for high-performance and powerful engines.

However, the smaller intake valves on the 862 heads offer better low-end torque for street applications. This feature gives the 862 heads a slight advantage when it comes to daily driving scenarios.

It’s evident that both the 862 and 706 heads have their unique characteristics when it comes to valves and port volumes:

  • 862 heads: Smaller intake valves and intake port volume.
  • 706 heads: Larger intake valves and intake port volume.

Performance and Efficiency

When it comes to power, both 862 and 706 cylinder heads offer decent performance for engines like 5.3L, 4.8L, and 6.0L.

However, some differences affect their efficiency.

862 Heads:

  • Small combustion chamber volume
  • Improved fuel and air flow
  • Larger valves
  • Larger intake port

706 Heads:

  • Similar to 862 heads in most aspects
  • Slightly superior due to semi-permanent mold (SPM) construction

Both cylinder heads have pros and cons in terms of performance.

Pros of 862 Heads:

  • Better fuel efficiency due to smaller combustion chamber volume
  • Increased power due to improved air and fuel flow, larger valves, and intake port

Cons of 862 Heads:

  • Might require modifications
  • Higher cost compared to 706 heads

Pros of 706 Heads:

  • SPM construction makes them slightly superior to 862 heads
  • More budget-friendly option compared to 862 heads

Cons of 706 Heads:

  • Slightly less efficient in terms of fuel and air flow compared to 862 heads
862 Vs 706 Heads - Which One Is Better

 

Materials and Manufacturing

When comparing 862 and 706 heads, it’s crucial to consider their manufacturing processes. The 706 heads are made using the SPM (semi-permanent mold) method, while the 862 heads employ sand-casting.

  • SPM heads:
    • More consistent process
    • Improved overall quality
    • Suited for temperature and pressure resistance
  • Sand-cast heads:
    • Slightly less consistent
    • Inferior temperature and pressure resistance compared to SPM heads

In terms of materials, both heads are made of aluminum. This lightweight metal is commonly used in automobile components like cylinder heads. Aluminum offers advantages such as:

  • Lightweight
  • Better heat dissipation
  • Corrosion resistance

Table comparing 862 and 706 Heads

Feature862 Heads706 Heads
MaterialAluminumAluminum
ManufacturingSand-castingSemi-permanent mold
ConsistencyLowerHigher
DurabilityGoodBetter

Casting Numbers and Variations

When comparing 862 and 706 cylinder heads, it’s essential to understand the casting numbers and variations. Both head types belong to GM’s Vortec line, primarily found on 4.8L and 5.3L truck engines.

In terms of casting numbers, these heads are identified as follows:

  • 862: Part numbers 12559862 and 12561706
  • 706: Part numbers 12559862 and 12561706

These casting numbers indicate that 862 and 706 heads are quite similar. They both have a combustion chamber volume of 61.15cc and a compression ratio of 9.5:1. The intake valve diameter is also the same at 1.89 inches.

It’s not only the 862 and 706 heads that are of interest in the LSx discussion. Other popular variations include:

  • 241: Found on 1997-2004 LS1 and LS6 engines
  • 243: Found on high-performance LS2, LS6, and LQ9 engines
  • 317: Found on 2001+ 6.0L truck engines (aluminum)
  • 799: Similar to 243 heads but found on Gen IV LS engines
  • 806: Found on 1997-1998 LS1 engines (aluminum)
  • 853: Found on 1999-2000 LS1 engines
  • 873: Found on 1999-2000 6.0L truck engines (cast iron)
  • 933: Found on 1997 LS1 engines up to mid-September

Although 862 and 706 heads share many similarities, the primary difference is that the 706 heads are made using SPM (semi-permanent mold) while the 862 heads are not. This makes the 706 heads slightly superior.

Cylinder HeadCasting NumberMaterialEngine Found On
86212559862Aluminum4.8L & 5.3L trucks
70612561706Aluminum4.8L & 5.3L trucks
241AluminumLS1 & LS6 engines
243AluminumLS2, LS6 & LQ9 engines

When comparing the 862 and 706 heads, their casting numbers and variations point to the 706 heads as slightly better mainly due to their SPM manufacturing process. They also share common traits, making either head a decent choice for an LS engine build.

Popular Cylinder Head Models

The market offers various cylinder head models, but the 862 and 706 heads often stand out. Both are popular options for LSX and truck engines, providing cost-effective performance upgrades.

862 Heads

  • Found in 4.8L, 5.3L, and 6.0L engines
  • Part of the Vortec head family
  • Excellent choice for high-performance builds

Made from semi-permanent mold castings, the 862 heads offer better flow and higher-quality materials than their counterparts. They hold a slight edge over the 706 heads in performance.

706 Heads

  • Used in 5.3L engines
  • Common alternative to 862 heads
  • Affordable and readily available

The 706 heads are similar in most aspects to the 862 heads. However, they are not made using the same semi-permanent mold casting process, resulting in slightly lower quality.

Feature862 Heads706 Heads
Engine Sizes4.8L, 5.3L, 6.0L5.3L
Casting MethodSemi-permanentStandard
PerformanceSlightly SuperiorComparable

Using CNC porting, both 862 and 706 heads can see significant improvements in airflow and performance. LS2 heads, another popular choice, provide more airflow by design, but might be more expensive.

Therefore, both 862 and 706 cylinder heads present budget-friendly options for upgrading LSX, truck, and Vortec engines. The choice between them comes down to individual preferences, budget, and build goals.

Applications and Market Availability

862 and 706 heads are both designed for use in GM vehicles, specifically the Chevy 5.3L Vortec engine, and have become popular options in the automotive cylinder head market.

Durability is crucial for both cylinder heads due to the high temperatures and pressures they must handle. The 862 heads are known for their improved fuel flow and larger intake port, while the 706 heads are made using semi-permanent mold (SPM) technology for added strength.

When it comes to supply, these cylinder heads are readily available. However, it is essential to verify their compatibility with your car before purchase. When making a decision, consider the following pros and cons of 862 and 706 heads:

862 Heads

  • Pros:
    • Small combustion chamber volume
    • Improved fuel and air flow
    • Larger valves
    • Larger intake port
  • Cons:
    • Modifications may be required
    • Higher cost

706 Heads

Pros:

  • SPM manufacturing
  • Slightly superior to 862 heads

Cons:

  • Smaller intake port

While both 862 and 706 heads are great choices for performance and durability, make sure to evaluate the affordability and market availability of each option.

862 Vs 706 Heads - Which One Is Better

 

Engine Cooling and Integration

862 heads:

  • Made of aluminum
  • Lightweight
  • Efficient heat dissipation

706 heads:

  • SPM (semi-permanent mold) made
  • Slightly superior to 862 heads

Comparison Table

Feature862 Heads706 Heads
MaterialAluminumSPM made
WeightLightweightSlightly heavier
Heat DissipationEfficientSlightly better

The aluminum construction of 862 heads contributes to better engine cooling. This material dissipates heat more effectively than alternative options. This enhances performance and improves fuel economy.

By maintaining optimal engine temperature, the integration of 862 heads in high-performance and race cars makes sense. The weight savings and rapid cooling capabilities are hard to overlook.

On the other hand, 706 heads, made through the semi-permanent mold (SPM) process, boast slightly superior cooling properties when compared to 862 heads. Consequently, 706 heads may be considered the secret weapon in budget engine builds.

Both engine heads offer their unique advantages in terms of cooling and integration. By understanding their distinct characteristics, one can make an informed decision for their specific automotive needs.

Common Modifications and Upgrades

When comparing 862 and 706 heads, there are several common modifications and upgrades to consider for optimizing performance.

CNC Porting

  • 862 heads: May require CNC porting to enhance air and fuel flow for increased horsepower.
  • 706 heads: Generally benefit less from CNC porting due to their semi-permanent mold construction.

Upgraded Springs and Retainers

  • Many enthusiasts upgrade valve springs and retainers for improved durability and performance.

For example, dual valve springs with lightweight titanium retainers for high-RPM applications

Horsepower Increament

  • Porting, polishing, and upgrading components can result in horsepower gains.
  • Results vary depending on the combination of modifications and the specific engine setup.

Here’s a comparison table showing some relevant aspects:

Feature862 Heads706 Heads
Casting ProcessSand-castingSPM (semi-permanent mold)
Potential UpgradesCNC porting, dual springs, titanium retainersLess emphasis on porting, dual springs, titanium retainers
Horsepower GainsVary based on modifications and engine setupVary based on modifications and engine setup

Conclusion

When it comes to choosing between 862 and 706 heads, understanding their unique characteristics is crucial.

Whether seeking improved fuel economy and performance with 862 heads or valuing the durability of 706 heads, selecting the right option depends on individual preferences and engine requirements.

Frequently Asked Questions

What are the performance differences between 862 and 706 heads?

Performance-wise, 706 heads are superior due to their consistency after porting, which results from the SPM casting method.

862 Heads

  • Cast method
  • May not be consistent after porting

706 Heads

  • Semi-permanent mold (SPM) method
  • More consistent after porting

How do 862 heads compare to 706 heads for boost applications?

862 and 706 heads have similar performance for boost applications. Their design allows both to withstand high temperatures and immense pressure in combustion chambers.

Are there any specific applications where 862 heads outperform 706 heads?

There are no specific applications where 862 heads significantly outperform 706 heads. However, 862 heads are considered a top choice for high-performing cylinder heads due to their ability to withstand high pressure.

What factors should be considered when choosing between 862 and 706 heads?

  • Performance consistency after porting
  • Casting method (SPM vs. Sand cast)
  • Power output requirements
  • Budget constraints

Which heads yield a higher power output, 706 or 862?

Power output does not differ significantly between 706 and 862 heads. However, the more consistent performance after porting offered by the 706 heads could lead to a slight advantage in power output for certain applications.

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Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

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