How Many Spark Plugs in a V8 Hemi? The Unique Configuration

With its hemispherical combustion chamber design, the Hemi engine has long been associated with high performance and is often celebrated for its power and efficiency. A staple among muscle cars and certain trucks, the V8 Hemi, in particular, is a well-known variant of this engine. But one interesting feature is how many spark plugs in a v8 Hemi.

how many spark plugs does a v8 have

How Many Spark Plugs in a V8 Hemi?

While the typical V8 engine will have eight spark plugs, one for each cylinder, the V8 Hemi uses a different configuration: two spark plugs per cylinder, leading to 16 spark plugs. This design is often called “Twin Spark” or “Dual Spark” technology.

The Benefits of Dual Spark Plugs

Why would an engine need two spark plugs per cylinder? The answer lies in the quest for more efficient combustion, improved fuel economy, and reduced emissions.

  1. Better Combustion – Utilizing two spark plugs per cylinder facilitates more efficient burning of the air-fuel mixture. This enhanced combustion process helps in extracting more power from each cylinder.
  2. Improved Fuel Economy – Thanks to the complete combustion, the V8 Hemi can make better use of its fuel, potentially leading to improved fuel economy. However, this is contingent on various factors, including driving conditions and maintenance.
  3. Reduced Emissions – The efficient combustion process also leads to lower emissions, as more fuel is burned, leaving fewer unburnt hydrocarbons and other pollutants to be emitted from the exhaust.
  4. Enhanced Durability and Reliability – Having two spark plugs per cylinder can extend the life of the spark plugs, as the load is distributed across more plugs, reducing wear and tear on each plug.

Maintenance Considerations

For those owning a V8 HEMI, the dual spark plug configuration does come with additional considerations:

  • Replacement Costs: With twice the number of spark plugs as a typical V8, replacing all the spark plugs will naturally be more expensive. However, the benefits in performance and efficiency often outweigh this cost for many owners.
  • Service Intervals: Consult the vehicle’s owner manual for the recommended spark plug replacement intervals. Thanks to advancements in spark plug technology, many modern spark plugs have longer service lives than their predecessors.

Do All V8s have 16 Spark Plugs?

No, not all V8 engines have 16 spark plugs. The standard configuration for most V8 engines is to have one spark plug per cylinder, making 8 spark plugs. However, some specific models mentioned above, such as certain versions of the Chrysler V8 Hemi engines, have adopted a “two spark plugs per cylinder” design, which makes a total of 16 spark plugs. This setup, known as a dual ignition system, helps promote better fuel combustion and increased fuel efficiency.

Always refer to the specific engine’s manual or technical documentation to confirm the exact number of spark plugs used in a particular V8 engine. Different manufacturers and engine models may adopt various configurations based on the design objectives and technology adopted at the time of manufacture.

changing spark plugs

How Often Should You Change Spark Plugs in a V8?

The frequency for changing spark plugs in a V8 engine can vary depending on several factors, including the type of spark plugs being used, the specific recommendations of the vehicle manufacturer, and the driving conditions the vehicle is subjected to. However, here is a general guideline to give you an idea of how often you might need to change the spark plugs in a V8 engine:

Copper Spark Plugs

These are typically found in older vehicles. They have a shorter lifespan compared to their platinum and iridium counterparts. Generally, they should be replaced every 20,000 to 30,000 miles.

Platinum and Double Platinum Spark Plugs

These offer more longevity compared to copper plugs. You should consider changing them every 60,000 to 90,000 miles. However, some might last up to 100,000 miles, depending on various factors.

Iridium Spark Plugs

Iridium spark plugs are known for their durability and can last up to 100,000 miles or more before needing replacement. Again, always refer to the manufacturer’s specific recommendations.

Factors Influencing the Lifespan of Spark Plugs

  • Driving Conditions: Harsh driving conditions can lead to more frequent spark plug replacements.
  • Engine Performance: If the engine is not running efficiently or is experiencing issues, it might necessitate more frequent spark plug changes.
  • Maintenance: Regular maintenance and tune-ups can help extend the life of spark plugs.

How Much to Change Spark Plugs in a V8 Hemi?

Changing spark plugs in a V8 Hemi, especially one with 16 spark plugs, is generally more expensive than a regular V8 due to the additional spark plugs and increased labor time. The labor involved can be quite intensive; hence it is always good to get an estimate before proceeding with the replacement. Here’s a general idea of the costs you might be looking at:

Cost of Spark Plugs

  1. Copper Spark Plugs: Generally ranging from $2 to $5 per plug, you would be looking at a total parts cost of $32 to $80 for 16 plugs.
  2. Platinum Spark Plugs: With prices generally ranging from $6 to $15 per plug, your total parts cost might be between $96 and $240 for 16 plugs.
  3. Iridium Spark Plugs: Typically costing between $8 and $20 per plug, the total parts cost for 16 plugs would be around $128 to $320.

Labor Costs

Labor costs can fluctuate significantly based on the workshop’s hourly rate. Replacing 16 spark plugs is a more time-consuming job compared to an 8 plug system. Generally, you might be looking at:

  • Dealership: Often ranging from $200 to $400 or more for the labor alone, considering it might take 2 to 4 hours to complete the job.
  • Franchise Repair Shop: Likely cheaper than the dealership, ranging from $150 to $350 for the labor.
  • Independent Mechanic: Potentially the most cost-effective option, with labor costs ranging from $100 to $300.

Total Cost Estimation

Combining both the cost of spark plugs and labor, the total cost for a spark plug change on a V8 Hemi engine might be roughly estimated as follows:

  • Basic Copper Spark Plugs: The total cost might range from $132 to $480.
  • Platinum Spark Plugs: Total cost might range from $246 to $590.
  • Iridium Spark Plugs: Total cost might range from $228 to $620 or more.

Keep in mind that these are estimates, and actual costs can vary, but don’t mix platinum and iridium spark plugs. Moreover, if the spark plug wires or coils also need to be replaced, this can add to the cost.


In conclusion, the V8 Hemi engine’s unique feature of housing sixteen spark plugs stands as an epitome of engineering excellence, promising augmented power, potentially improved fuel efficiency, and reduced emissions. This distinctive characteristic showcases the innovative spirit that drives the continuous evolution of automotive technology, ensuring that the V8 Hemi remains a significant player in high-performance engines.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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