DIY - Spark Plug Indexing

[SVOboy]

Doing a tune up? Replacing spark plugs? Just wanting to check things out? While you're at it consider indexing your spark plugs. This is one of the few ignition modifications that can make a very small difference in engine performance. As said by the folks at Advance Auto Parts: "Real-world power gains vary. Some engines or combinations respond differently than others. In fact, all engines will pick up power, but some gains will be more dramatic than others.In the end, it can't hurt to index the spark plugs. This can contribute to superior engine efficiency and improved economy." So, no promises, but it can't hurt!

Purpose: Indexing the plugs allows the flame to spread more uniformly through the combustion chambers in the individual cylinders. I am certainly not about to claim a plethora of scientific knowledge on the subject but I've seen many dyno charts supporting the theory and have thus accepted the idea that it'll help. It's really not too much extra effort on top of replacing the plugs, so what the heck.

Time: 20 minutes

Tools:
- Socket Wrench
- Spark Plug Socket
- Extension

Supplies:



1. Go to the parts store and buy yourself some new spark plugs, preferably Denso U-Grooves or NGK V-Powers (basically the same). They're the recommended stock replacement and generally used plugs; cheap and effective. Again, I do not profess to be a spark plug wizard.
2. Pop them out and take a look at how they get their name.


3. Mark with a marker the on the white part where the opening on the plug is. This will allow you to see where the opening it when the plug is in the head getting adjusted.

4. Go out to the car, yank your plug wires and then your old plugs.




5. Stick a new plug in and tighten it down and see where the opening is. On most cars you'll want the opening facing the exhaust, but it's different for everybody.
6. If it lines up perfectly stock, you're lucky, if not, grab a copper indexing washer and throw it on the bottom of the plug and see how it works. There are different sizes of washers and all that to try and get the indexing right, so just mess around until you get it.

See if you can see how it's lined up:


7. Once they are all indexed, slap everything together and be happy.

There are two methods of indexing, one is to buy lots of plugs and attempt to get lucky, the other is to use washers, take your pick. I chose to use washers rather than to try my luck. Less wasted gas driving to the store.

Read your old plugs!

[DAN]

you know they once said washers mess up plugs heat rating nascarr does this but they do a lot of work with how hot ot cold their plugs are. i think but thats only what i think, it matters with high reving, very high c.r race motors. but i just don't know about street use.

[Ryland]

the copper indexing washers shouldn't screw with the heat range that much, after all you already have a steel (not thermoly conductive) gasket washer on the spark plug, and 3/4" of threds that are tightly meshed with the cylender head.
I am however having truble finding indexing washers.

[budomove]

Great write up, Ben!

I have the new specially indexed "b" plugs I have yet to put in on the insight, and they supposedly need to be tightened to precisely 15ftlbs, or the indexing and hence mpg will be off. I will wait to get a torque wrench I guess. Does anyone know if this is really true?

Frank

[Chris D.]

lots of dead pictures

I've been looking into doing it too..

I'd think that using the washers would slightly lesson the compression
per cyl by a fraction making things to be slightly unbalanced..

just a theory..

[brucepick]

I tried to find indexing washers but nobody local had them in stock.

I indexed my plugs without washers on two tuneups now. I did it by buying a couple extra sets. That way I keep trying plugs till I find the ones where the gaps point where I want.

You do end up with extra plugs this way. But we have other cars in the family that take the same plugs so I know they'll get used.

One thing I learned is that you have to learn, for your current brand plug, how many additional degrees of tightening it will take for it to get fully seated. That is, you don't want to crank down a plug completely to learn that it's off by 10-15 deg.

My current NGKs need about 3/4 additional turn after they first make contact. So I test-fit them in different holes till I find one that's right - so after I give it the additional 3/4 turn it will be aimed right.

They used to say that gasketed plugs need 1/4 turn, if I recall. But that's very old-schoool, mine need 3/4 turn and yours may be different.

[diesel_john]

might save a little time mark the old plugs before you take them out. get one fine thread 14mm nut and you can reference from your old plug to your newplug.

[metroschultz]

Allrighty Ben,
How come I can not see your pics.
Ever
On any thread
is it me? something in my firewall maybe?
Do I need to get My CompuGeek Son over here to De-Bug this issue.
You know he really loves being disturbed for stuff I should already know how to do.

Bruce, I think you have that Backward
Plugs with gasket usually require 3/4 turn after contact.
Plugs with conical seal usually require only 1/4 turn after contact.
Buying and marking many plugs will lead to a mass
Plug Rehabilitation. I just gave Ralph 39 spark plugs to use at his shop.
Talk to your Parts Chick, (the girl behind the counter)
you know which way the plugs need to set for index.
Check the beginning of the first thread against the position of the ground electrode.
Ask your parts people if they will let you open the random boxes of plugs till you get the ones you need.Then you only take what you can use.
You might still want a couple extra.
Saves having to toss a bunch you won't use.
S.

[tasdrouille]

I don't get it why they don't make the plugs all the same from the factory. It would be so much simpler and everyone would benefit from it.

Check the beginning of the first thread against the position of the ground electrode.

Thanks for the tip!

[Ryland]

Originally Posted by tasdrouille

I don't get it why they don't make the plugs all the same from the factory. It would be so much simpler and everyone would benefit from it.



Thanks for the tip!

Honda did that for the Insight, then they put a letter stamp next to each hole to tell you what spark plugs fit what hole.

making things like threds exactly the same is not as simple as you might think, you can do it with a lathe, but that takes more time, and costs more money.