How To Protect Spark Plug Wires From Headers : Most Effective Solution

Engine headers are extremely hot because they exhaust the burnt fuel from the engine. But spark plugs are usually very close to engine headers. So, how to protect spark plug wires from headers?

Well, the simple solution to this problem is to install fiberglass sleeves on the spark plug boots. You can acquire extra protection by installing additional thermal sleeves on the spark plug wires as well (under the fiberglass sleeves).

Now, don’t worry. Installing fiberglass spark plug boot sleeves is a simple and DIY job.

However, to pull off this task neatly, you’ll need an easy and effective guide. Luckily for you, it’s given in the discussion below. So, go ahead and have a brief read.

Protect Spark Plug Wires From The Headers: Understanding The Problem

In order to protect your spark plug wires from your engine headers, you must understand the physical structure of spark plug wires and engine headers.

So, let’s see the image below and comprehend this issue before attempting to solve it:

spark plugs wire & engine header

As you can see from the image above, spark plugs usually exist in extremely close proximity to the engine headers.

So, since they’re very close, you need to insulate them by something that does not conduct heat at all. And the best material for that is fiberglass sleeves.

How To Protect Spark Plug Wires From Headers?

As already indicated above, you have to install fiberglass sleeves or additional thermal sleeves to protect your spark plug wires. This will act as two-layer protection against the engine headers.

Now, let’s see the detailed steps of these solutions so you can easily protect your spark plugs from your engine headers’ heat.

1. Installing fiberglass spark plug boot sleeves:

Installing the fiberglass sleeves on your spark plug boot is really straightforward. All you have to do is follow the simple steps below:

  1. You can buy fiberglass sleeves from online marketplaces or you can also grab one from your local automobile shop.
  2. Then, you have to pop up your engine bonnet and pull off the spark plug wire. Check the image below for a better understanding:
spark plug wire
  • Next, you should apply some dielectric grease on the spark plug boot and the spark plug wire. This will make sure that the fiberglass sleeve is easily fitted onto the spark plug wire.

Plus, applying the dielectric grease will make sure that you can easily remove the fiberglass sleeve whenever you want to.

  • Now, simply grab the bottom portion of the spark plug wire (the opposite end of the spark plug rubber boot) and shove it into the fiberglass sleeves.
  • After that, pull up the fiberglass sleeve all the way in. At this point, the sleeve should mostly cover the spark plug wire. Check The picture below to have it clearer understanding:
covering a sleeve spark plug wire
  • Finally, all you have to do is reinstall that spark plug wire to the engine in its former position. And, just like that, you’re done installing the fiberglass sleeve.

Now, you can rest easy knowing that your spark plug wires will never get burned again.

2. Installing additional thermal sleeves:

Alongside installing fiberglass sleeves on your spark plug boot, you might also need to install additional thermal sleeves. It’s because sometimes spark plug wires are too long for fiberglass sleeves to cover.

In those situations, you’ll have to install spark plug thermal sleeves to cover the whole spark plug wire. After that, you can install the fiberglass sleeve on top of the thermal sleeve to provide your spark plug wires better protection.

Why Do I Need To Protect My Spark Plug Wire From Engine Headers?

Engine headers will immediately burn the spark plug wires when in contact. This is the first and foremost reason why you should keep your spark plug wires safe from engine headers. So, you’ll have to replace spark plug wires very frequently if you don’t protect them from the engine headers.

However, there’s another important reason as well. If your spark plug wires are not well insulated from the engine headers, the spark plug wires will get extremely heated by the engine headers.

As a result, more resistance will build up in the spark plug wires, and the electric flow will be hampered. Consequently, unnecessary heat can build up in the spark plug, and it can explode. 

Remember, excessive heat is also what causes spark plug electrodes to bend and be permanently damaged. So, it’s indispensable to insulate your spark plug wire from the engine headers if you want your spark plug wires to be durable.

Furthermore, as you may well know, people commonly ask on the internet, “why does my spark plug wire keep popping out? Well, it’s because of unexpected heat generation in the spark plug.

Now, since separating the headers and the spark plug wires also prevent all sorts of meltdowns in the spark plug, it will also solve the issue of spark plug wires popping out unexpectedly.


Well, that’s all there’s to it, people. Now that you have got a clear understanding of this query, how to protect spark plug wires from headers?

To wrap it all up, you only have to use insulating sleeves on your spark plug boots. And the best option for that is to use fiberglass-based spark plug boot sleeves.

Thank you so much, and peace out!!!

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