How To: Change Your Spark Plugs (valid for most cars prior to coil-on-plug systems)

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How To: Change Your Spark Plugs (valid for most cars prior to coil-on-plug systems)

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It seems so basic, yet here is a pictorial step by step guide to properly changing out your spark plugs (Ferrari 348 used as demonstrator), including one step that I'll bet most people haven't heard about (or have been taught incorrectly).

Here's what you'll need:

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new spark plugs (8 for the 348)
Spark plug socket (18mm for NGK and Splitfire)
Socket extension
Ratchet (flex handle preferred)
Feeler gauge (to gap old-style plugs, but not for Iridium of any brand, Bosch+4, or Splitfire plugs)
dielectric grease
anti-seize compound
Clean rag (disposable)
shop gloves
long nose pliers (in case your spark plug socket has trouble removing a plug from your block after it's been unscrewed)
Stabilant 22a (RicambiAmerica.com), Marine Corrosion Block (West Marine), or other suitable electrical contact enhancer
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With your engine off and cold (not hot!), pop your engine bonnet and wipe-off or blow off any surface dirt on around your spark plug boots.

You are now going to begin a repeating process of removing and then replacing one spark plug at a time. By doing one at a time, you won't risk connecting plug wires in the wrong order. Minimizing risk is a nice thing.

 

THE CYCLE

With gloves on, grasp the underside of the rubber boot as shown
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Twist it 1/4 turn clockwise, then counter-clockwise to "break" it from where it has been sitting on your spark plug, then twist it in either direction as you lift up on the boot so as to remove the plug wire from the spark plug.

Always apply force to the boot on the end of the plug wire, never on the wire itself.

With the plug wire removed, apply Stabilant 22a to the metal contact areas inside the rubber boot of the spark plug wire, then let the plug wire dangle...leaving open a path to its spark plug.

With your spark plug socket attached to its extension and mounted to your ratchet, insert your socket into the block path so that it locks onto the base of the spark plug (hint: turn it a bit clockwise/counterclockwise to feel the socket grip against the spark plug).

Set your ratchet to loosen, and apply counter-clockwise pressure to unbolt/unscrew your spark plug.

Pull your sparkplug out with your attached spark plug socket (if your socket fails to adequately grip your spark plug, just insert your long-nose pliers and grab the now-unscrewed spark plug by its metal cap end to remove) as shown:
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Line up each used spark plug sequentially (labeling/numbering is a good idea) so that you can later photograph and analyze your engine's condition based on the debris/wear on each plug. These should be out of the way.

 

Pick up a new spark plug, and if it a type that should be gapped (e.g. Champion), then measure its gap by inserting your feeler gauge between the plug's ground and electrode, rotating the gauge until it "sticks" or touches at both the top and bottom.

Ferrari 348 plug gaps should be .028 inches wide, as shown:
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If the gap needs to be adjusted, grasp its curved ground from behind or above with your long nose pliers and bend in the appropriate direction to widen or shrink the gap to the desired distance. Do *not* insert a feeler gauge or flatblade screwdriver under the ground. Do *not* use the center electrode as leverage to change the gap distance. This can do unseen damage to the plug, including knocking platinum/iridium off of the electrode or even breaking the plug physically. Touch only the curved ground, not the central electrode.

 

Once the spark plug is confirmed to be correctly gapped, unscrew the metal end cap and apply Stabilant 22a to the internal threads as shown:
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After applying Stabilant 22a or Corrosion Block, screw the metal cap back on hand tight.

Put a small amount of anti-seize compound onto the middle third of the new spark plug's threads (leave 1/3 of the threads near the electrode uncoated, leave 1/3 of the threads near the ceramic base uncoated) as shown:
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Here's a bit about High Voltage (great AC/DC reference, by the way). High voltage wires leak.
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To stop some of the leakage from high voltage wires, there is a great solution called a "dielectric."

A dielectric is what is used in between metal plates in capacitors...it won't conduct electricity very well until a severe level is reached (at which point electricity jumps through it or over it).

Anyway, the point is that something called a "dielectric" doesn't ordinarily conduct electricity very well.

Some clever folks have also combined several properties such as being "dielectric" and being a lubricant and being a water repellent.

 

So what we want to do is take advantage of the clever minds at Loctite et al.

We want to apply dielectric grease onto the **CERAMIC** of our new spark plug.
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The moral of the story is that you do not want dielectric grease on any of your metal conducting surfaces.

Here's Loctite's story: http://tds.loctite.com/tds5/docs/DIEG-EN.pdf

Because dielectrics don't conduct very well...they add resistance to metal if they are applied in between metal surfaces...reducing spark.

But if you correctly put dielectric grease only on the ceramic base of your new spark plug, you'll prevent some high voltage leakage that will give you **MORE** spark voltage/power.

Plus, the grease will keep out moisture from humidity and washes, reducing rust, etc.




And this is likely very different from what you've ever heard about dielectric grease. I've even got one brand of dielectric grease that says on its own package the opposite of the above, so some pros aren't immune to misinformation.

 

With your new spark plug now gapped, anti-seized, and coated on its ceramic base with dielectric grease, place it into the plug socket and insert it back into the engine block to replace the old spark plug.

But...remove your ratchet from the socket and extension such that you can hand-tighten your new spark plug into the block.

Once hand-tight, set your ratchet to tighten and apply pressure for 1/4 turn. Do not use so much pressure that you "GRUNT" while installing your plug! Don't overtighten.

Remove your socket and press-fit your spark plug wire boot back on.

END OF CYCLE

Repeat the above cycle for each spark plug in your engine.

 

Optional New Cycle

If desired, pull off one plug wire boot from one coil. Coat the internal metal contacts (of coil and plug wire) with Stabilant 22a, apply the tiniest bit of dielectric grease to the rubber of the boot, and reconnect the plug wire back onto the coil.

End of Optional New Cycle

Repeat the above for each additional plug wire/coil conection.



Put up all tools (count them to be sure!).

Close engine bonnet. Start engine. Verify good operation.

Now drive!
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To read your old spark plugs: http://www.ferrarichat.com/forum/showthread.php?t=121401

 

In the controversial part above, what you are doing with the silicon dielectric grease is making a watertight seal between the ceramic base of the spark plug and the rubber boot of the spark plug wire.

That keeps out moisture, preventing corrosion/rust on your spark plugs and wires.

And, since that grease is also a dielectric, your watertight seal (above) also keeps *in* electricity that would otherwise leak out (into the air or jumping to your nicely grounded engine block) of your spark plug wire connections as high voltage likes to do.


So you keep water out, and keep extra voltage/current in...all by putting a little dielectric grease onto the ceramic of the spark plug.

 

Nice tip!

You are so right, Martin. Good job. I hadn't even thought about copper.



(I used petroleum-based anti-seize compound in the example for this thread, is that OK for aluminum blocks?)

 

Nice tips. Thanks again.


( for grins, here's a spark plug anti-seize compound that has all of the above in it, aluminum, copper, and graphite! http://www.permatex.com/products/automotive/b_lubricants/specialty_lubricants/Permatex_Anti-Seize_Lubricant_a.htm )