How to Change Spark Plugs 5.7 Hemi

Changing the spark plugs on your 5.7 Hemi engine is a highly rewarding DIY task that can significantly improve your vehicle’s fuel efficiency and performance. By following this guide, you will learn how to safely replace all 16 plugs to keep your engine running at its peak potential for years to come.

If you own a vehicle equipped with the legendary 5.7 Hemi engine—whether it is a RAM truck, a Dodge Charger, or a Chrysler 300—you know that this powerhouse is built for performance. However, keeping that performance alive requires routine maintenance. One of the most important, yet often intimidating, maintenance items is changing your spark plugs. Because of the Hemi’s unique dual-spark setup, many owners assume they need to take their vehicle to a shop. The truth is, you can tackle this job right in your own garage with the right guidance.

In this guide, you will learn exactly how to change spark plugs on a 5.7 Hemi. We will walk you through the preparation, the removal process, and the installation of the new plugs. By the end of this article, you will have the confidence to handle this task like a pro, saving yourself hundreds of dollars in labor costs along the way.

Key Takeaways

• Double the Plugs: The 5.7 Hemi uses a dual-spark system, meaning you must replace 16 spark plugs, not the standard 8 found in most V8 engines.
• Access is Key: Because of the engine bay configuration, you will need a few different extension lengths to reach the plugs hidden near the firewall.
• Avoid Forcing: Spark plugs should thread in by hand; if you feel resistance, stop immediately to prevent damaging the aluminum cylinder heads.
• Gap Matters: Always verify the gap of your new plugs, even if they are marketed as pre-gapped, to ensure optimal combustion.
• Safety First: Never attempt this job while the engine is hot; wait for the engine to cool down to protect your hands and prevent cross-threading.

Quick Answers to Common Questions

How often should I change my 5.7 Hemi spark plugs?

Most manufacturers recommend changing spark plugs every 100,000 miles. However, if you notice rough idling or reduced fuel economy, it might be time to check them earlier.

Do I need to use anti-seize on the plug threads?

Most modern spark plugs come with a specialized coating that makes anti-seize unnecessary. Check the manufacturer’s recommendations on the plug packaging before applying any compounds.

What if I break a spark plug during removal?

If a plug snaps, do not panic. You will need a specialized screw extractor set to remove the remaining threads from the cylinder head; if you are uncomfortable doing this, call a professional mechanic.

Can I use any spark plug for my Hemi?

No, it is highly recommended to use the specific plug part number listed in your owner’s manual. The Hemi engine is designed to operate with specific heat ranges and electrode materials.

Is it okay to change only some of the plugs?

Always replace all 16 spark plugs at once. Replacing only a few can cause imbalances in engine performance and may lead to further ignition issues down the road.

Step-by-Step Removal Process

Step 1: Accessing the Ignition Coils

Once your engine is cool, open the hood and remove the engine cover. Most 5.7 Hemi engines have a large plastic beauty cover that simply pulls off. You may need to give it a firm tug to release the rubber grommets holding it in place. Once removed, you will see the ignition coils sitting on top of the valve covers. There are eight coils in total, each held in place by a single 10mm bolt.

Step 2: Removing the Ignition Coils

Start with one bank of the engine at a time. Disconnect the electrical connector for each coil by pressing the release tab and pulling gently. If the plastic is brittle, be extra careful. Once the connector is off, remove the 10mm bolt and pull the coil straight up. You will see the spark plug hidden deep inside the spark plug tube.

Step 3: Removing the Spark Plugs

Attach your 5/8-inch spark plug socket to a long extension and insert it into the tube. Ensure it seats firmly on the spark plug hex. Use your ratchet to turn counter-clockwise to loosen the plug. Once loose, remove the plug carefully. Repeat this for both plugs in the cylinder before moving on to the next.

Installation: Doing It Right

Step 1: Gapping and Preparing the New Plugs

Before installing, check the gap of your new plugs using a gap tool. The manufacturer’s specification is crucial for engine performance. If the gap is off, gently adjust the ground electrode until it meets the spec. Apply a tiny amount of dielectric grease to the inside of the spark plug wire boot (if your model has wires) or the interior of the coil pack boot to prevent future sticking.

Preparation and Safety

Before you pop the hood, you need to ensure you have the right environment and equipment. Working on a 5.7 Hemi requires patience, especially because you are dealing with 16 individual spark plugs. Start by parking your vehicle on a flat, level surface and letting the engine cool completely. Working on a hot engine is a recipe for burnt knuckles and, more importantly, can damage the delicate threads in the aluminum cylinder head.

Gather all your tools beforehand. You will need a spark plug socket (typically 5/8 inch), a ratchet, a few different lengths of socket extensions (a 3-inch, 6-inch, and maybe even a swivel/wobble extension), and a torque wrench. Having everything laid out on a clean workbench or a tray will make the process go much faster and keep you from searching for tools with greasy hands.

Understanding Your 5.7 Hemi Requirements

The 5.7 Hemi is unique because it utilizes a “dual-spark” ignition system. Each cylinder has two spark plugs. This design helps the engine burn fuel more efficiently, resulting in better power delivery and cleaner emissions. This means when you go to the parts store, you are not buying eight plugs; you are buying sixteen. Make sure you consult your owner’s manual or check your engine’s specific year to ensure you are buying the correct type—usually iridium or platinum—recommended by the manufacturer.

Tools and Materials

To successfully complete this project, you need to have a clear inventory of the tools required. Refer to the table below to ensure you have everything ready before you start.

Tools and Materials

Required tools for a 5.7 Hemi spark plug replacement.

Tool	Purpose
5/8″ Spark Plug Socket	Removes and installs the plugs.
3/8″ Drive Ratchet	Provides the leverage to loosen plugs.
Extension Set (3″, 6″, 10″)	Reaches deep-seated plugs near firewall.
Torque Wrench	Ensures correct tightness of plugs.
Spark Plug Gap Tool	Verifies the gap is within specification.
Dielectric Grease	Protects ignition wire boots.

Step 2: Threading by Hand

This is the most critical part of the job. Never use a power tool to start a spark plug. Thread the new plug into the cylinder head by hand using only the socket and extension (no ratchet). You should be able to turn it most of the way by hand. If you feel any significant resistance, back it out and start over. Forcing a plug will strip the threads, leading to a very expensive repair.

Step 3: Torque to Specification

Once the plug is hand-tight, use your torque wrench to finish the job. The 5.7 Hemi typically requires a specific torque value—check your owner’s manual or the packaging of your spark plugs. Generally, it is between 13 and 18 foot-pounds. Do not overtighten, as you can damage the seal or the threads.

Troubleshooting Common Issues

Sometimes things do not go as planned. If you encounter a plug that is stuck, do not force it. Use a high-quality penetrating oil and let it sit for a few hours before attempting to loosen it again. If you notice the old spark plugs look oily or have heavy white deposits, this could indicate an underlying issue like a failing valve seal or an overheating engine. Always inspect the old plugs for clues about your engine’s internal health.

If the engine misfires after you have finished the job, double-check your ignition coil connections. It is very easy to forget to click one of the electrical connectors back into place. Also, ensure the rubber boot of the coil pack is fully seated over the spark plug; if it is loose, the spark will arc to the cylinder head instead of jumping the plug gap.

Conclusion

Changing the spark plugs on your 5.7 Hemi is a manageable project that pays dividends in vehicle longevity and reliability. While 16 plugs might sound like a daunting task, it is simply a matter of taking it one cylinder at a time. By preparing your tools, working methodically, and paying close attention to the installation process, you can ensure your Hemi continues to provide that signature roar for years to come. Take your time, enjoy the process, and take pride in knowing you handled your own maintenance.