Best Spark Plugs For Sbc 350 With Headers

So, you've got a small block Chevy 350 with headers – classic combination! But are you experiencing some common issues that often come with this setup, like poor idle, misfires, or reduced fuel economy? One of the prime suspects is often the spark plugs. Getting the right spark plugs for your specific SBC 350 and header configuration is crucial. Let's dive into how to choose the best ones and troubleshoot some common problems.

The Problem: Mismatched Spark Plugs and Header Issues

Headers, while fantastic for improved exhaust flow and performance, can drastically alter the engine environment around the spark plugs. Specifically, headers can lead to:

Increased Cylinder Head Temperature: Headers typically run hotter than stock manifolds. This can lead to pre-ignition (spark plug firing too early) or detonation (uncontrolled combustion), both of which can damage your engine.
Leaner Air/Fuel Mixture: Improved exhaust scavenging from headers can sometimes lean out the air/fuel mixture, particularly at higher RPMs. A leaner mixture burns hotter and can cause spark plugs to overheat.
Spark Plug Wire Proximity: Headers often run close to the spark plug wires. Excessive heat can degrade the insulation on the wires, leading to misfires, especially if the wires are old or of poor quality.
Physical Obstruction: Sometimes, the larger diameter of headers can make accessing the spark plugs difficult, requiring specialized tools.

Using the wrong spark plugs can exacerbate these problems. Stock replacement plugs might not be adequate for the higher temperatures and altered engine conditions. This can manifest as:

Hard starting: A weak spark can make it difficult to ignite the fuel mixture, especially in cold weather.
Rough idle: Misfires due to inadequate spark can cause the engine to stumble and idle unevenly.
Poor acceleration: A weak or inconsistent spark will hinder the engine's ability to produce power.
Reduced fuel economy: Incomplete combustion due to spark plug issues wastes fuel.
Engine knocking or pinging: This is a sign of pre-ignition or detonation and can cause serious engine damage.

The Solution: Selecting the Right Spark Plugs

Choosing the best spark plugs for your SBC 350 with headers involves considering a few key factors:

1. Heat Range:

Understanding Heat Range: The heat range of a spark plug refers to its ability to dissipate heat. A "hotter" plug retains more heat, while a "colder" plug dissipates heat more quickly. Headers often necessitate a colder spark plug.

How to Choose: If you're experiencing issues like engine knocking or pinging after installing headers, try going one step colder on the spark plug heat range. Most spark plug manufacturers use a numerical system, where a higher number indicates a colder plug (e.g., a 7 is colder than a 6 in the NGK system). Consult your engine builder or a trusted mechanic for specific recommendations based on your engine modifications and driving style. If you aren't experiencing any knocking or pinging, sticking with the stock heat range or going one step colder is a good starting point.

2. Spark Plug Material:

Types of Materials: The most common spark plug materials are:

Copper: Copper spark plugs are the least expensive and offer excellent conductivity, resulting in a strong spark. However, they have the shortest lifespan. These are a good choice for naturally aspirated engines without forced induction and if you don't mind replacing them more often.
Platinum: Platinum spark plugs offer longer lifespan than copper plugs and require less voltage to fire. They are a good middle-ground option.
Iridium: Iridium spark plugs are the most durable and offer the best performance, especially in high-performance applications. They also require very little voltage to fire and can last for many miles. Iridium plugs are an excellent choice for boosted applications or engines that are regularly run hard.

Recommendation: For an SBC 350 with headers, platinum or iridium spark plugs are generally recommended. They can better withstand the increased heat and last longer than copper plugs. Iridium plugs, while more expensive, provide the best performance and longevity.

3. Spark Plug Gap:

The Importance of Gap: The spark plug gap is the distance between the center electrode and the ground electrode. The correct gap is crucial for optimal combustion.

How to Set the Gap: Consult your engine's specifications for the correct spark plug gap. A general rule of thumb for SBC 350 engines is between 0.035" and 0.045". Use a spark plug gapping tool to carefully adjust the gap. Do not force the electrodes; you could damage them.

4. Physical Size and Fit:

Thread Size, Reach, and Hex Size: Ensure that the spark plugs you choose have the correct thread size (usually 14mm for SBC 350), reach (the length of the threaded portion), and hex size (the size of the socket needed to install the plug). Also, be sure the physical length of the plug doesn't interfere with your headers.

Check Clearance: With headers installed, space can be tight. Double-check the clearance between the spark plugs and the headers to prevent any contact that could damage the plugs or headers. Sometimes, using spark plug socket extensions or swivel sockets can help with installation and removal.

Practical Tips and Tools

Tools Needed:

Spark plug socket (typically 5/8" or 13/16")
Spark plug gapping tool
Torque wrench
Socket extensions and swivel sockets (especially helpful with headers)
Anti-seize compound
Spark plug wire puller (to avoid damaging the wires)
Work gloves

Installation Tips:

Disconnect the battery: This is a safety precaution to prevent electrical shocks.
Work on a cool engine: Never attempt to remove or install spark plugs on a hot engine.
Apply anti-seize compound: Lightly coat the threads of the new spark plugs with anti-seize compound to prevent them from seizing in the cylinder head.
Torque to specification: Use a torque wrench to tighten the spark plugs to the manufacturer's specified torque. Overtightening can damage the cylinder head, while undertightening can cause leaks. A common torque spec for 14mm spark plugs in aluminum heads is around 15-20 ft-lbs.
Inspect spark plug wires: Replace any damaged or deteriorated spark plug wires. Consider using heat-resistant spark plug wire boots if the wires are close to the headers.
Apply dielectric grease: Apply a small amount of dielectric grease to the inside of the spark plug wire boots to prevent corrosion and ensure a good connection.

Troubleshooting Common Problems:

Misfires: If you're still experiencing misfires after replacing the spark plugs, check the spark plug wires, distributor cap and rotor, and ignition coil.
Engine knocking or pinging: If the knocking or pinging persists after using colder spark plugs, consult a mechanic to investigate potential issues with the engine timing or fuel mixture.
Difficult access: If you're having trouble accessing the spark plugs due to the headers, consider using spark plug socket extensions or swivel sockets. Some headers may require removing them partially or fully to access the spark plugs.

Approximate Repair Costs:

Spark plugs: A set of 8 spark plugs can range from $20 for basic copper plugs to $100 or more for high-performance iridium plugs.
Spark plug wires: A new set of spark plug wires can cost between $30 and $100.
Labor: If you choose to have a mechanic install the spark plugs, labor costs can range from $50 to $150, depending on the accessibility of the plugs and the mechanic's hourly rate.

Pro Tip: Regularly inspect your spark plugs. The condition of the spark plugs can provide valuable insights into the health of your engine. Examine the electrodes for signs of wear, fouling, or damage. Comparing the appearance of your old spark plugs to spark plug reading charts can help you diagnose engine problems such as rich or lean mixtures, oil consumption, or coolant leaks.

By carefully selecting the right spark plugs and following these tips, you can ensure that your SBC 350 with headers runs smoothly and efficiently for years to come. Remember, when in doubt, consult a qualified mechanic for personalized advice tailored to your specific engine setup.