How to index spark plugs.

So yesterday the indexing washers came for the Metro. As with almost everything in this car, I expected to find near original equipment condition plugs in need of replacement. Oddly, it was the one thing that had been replaced. The plugs were dated 2006, and were Bosche. I've never heard good things about Bosche spark plugs, and as I was pulling them I marked their alignment with a Sharpie. Every one of them was aligned with the electrode shielding the valve. One thing I can say for the plugs, is they were manufactured uniformly. In essence, these spark plugs were "aimed" towards the wall of the head, rather than the fuel mixture. Exactly what indexing is meant to prevent.

What is indexing? Well it's just that, aiming the open end of the spark plug away from the walls of the combustion chamber and towards the center of the valves. Some engines produce significantly more power by indexing, some don't. It only costs a few washers, and a couple extra minutes, so the consensus is if you're going to change your plugs, then do it right, and index them.

It's really simpler than it sounds. Basically just like the plugs I removed, you mark the open end of the spark plugs with a Sharpie. Install and see where it lines up. If it's "straight up" or within 30 degrees of 12 o'clock then you're indexed. If they align differently, then by adding a indexing washer (they come in varying thickness) eventually you get the correct position.

Patience is a virtue, but I managed indexing my three cylinder in under 20 minutes. Simply, try it with no indexing washer, then if incorrect add the thinnest one, and move up from there.

When done, you should have a smoother running more balanced engine that could produce more horsepower and better MPG.

I'll report back in a week or so, to see if I record any difference on my fuel log, but I already have a sense of contentment knowing I'm doing all I can to make my engine as happy as possible.

I know there is some argument to whether indexing actually works, but I have seen dyno numbers, and drag times to suggest it does. Need further proof? Honda engineers color code specific spark plugs on the Honda Insight to make that engine "indexed", which allows the vehicle to produce the high gas mileage it does.

Think of it like this. There's a bomb in the room you're in right now, and it's sitting by the wall. It's about to explode. If there's nothing blocking its way, it will explode and radiate out from where it explodes out into the room killing everyone. On the other hand, if you were to run over to the bomb and use your body as a shield, you would, in fact absorb some of the blast and prevent the bomb from radiating (at least to the same degree) out into the room. In the combustion chamber, you, are the electrode, shielding the explosion in the room (combustion chamber). The difference is we want the big explosion, we want everyone to die. So by turning the electrode to the optimal position through indexing, you can blow up all those evil air and fuel molecules in the engine. Death, destruction, mayhem on the inside, yet on the outside you might be saving the world...

I'm all about saving money (gas), and maybe even the environment to boot. If twenty minutes of time isn't worth the benefits of both, than it's certainly worth my clear conscience.


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