Indexing Spark Plugs

[Virg464]

Does anyone index their spark plugs? I remember reading an article about doing that, suppose to help with ignition/flame formation? It sounds way past what I'm building but I'm curious if it's really done and if so, whats tangible advantage... if any?

 

[pnora]

To me its a total waste of time. Does it work????? Will you notice the difference????????????????

 

[INTMD8]

I do. I buy multiple sets and swap them around until they are indexed how I want them.

May be a waste of time but it's the kind of time wasting I don't mind doing.

 

[Virg464]

To me its a total waste of time. Does it work????? Will you notice the difference????????????????

That's what I'm wondering, if someone tried it at the track after running non-index plugs and what diff did they see at the end of the track?

 

[R413]

@GTX JOHN may have experience with this.

need to run the car and see the numbers to know if it’s worth it.

 

[zyzzyx]

Used to race a Big Block Chevy in the mid 70's and we bought the shim washers and indexed the plugs.
Don't know if it was worth anything????

 

[furious70]

Engine masters really needs to test this one!

 

[Jeff Peterson]

I think this speaks for itself on indexing plugs....

early photo of a Cammer with the original spark plug location. Ford engineers took great pains to design a perfectly symmetrical hemispherical combustion chamber with an optimized spark plug location, only to discover that the spark plug didn’t really care. The plugs were then relocated at the top of the chamber for ease of access.

 

[33 IMP]

To me , indexing the plugs was for maximum effort engines with sky-high domes on the pistons, with sky-high compression ratios. The idea was so the piston didn't smash the gap closed and destroy the plug. Directing the spark down into the chamber was an added benefit.
If you don't have a 14 to 1 engine, I wouldn't bother.....

 

[GTX JOHN]

@GTX JOHN may have experience with this.

need to run the car and see the numbers to know if it’s worth it.

I am lucky when I find a Hundred by indexing! Both the big and small blocks prefer
to have them pointed towards the exhaust valve I have found. I do not know why.

At Denver at Nationals some years ago = I won Class Race by .0001 against another
very fast 340 car.

Sometimes a little bit means the World in what I do.
Bracket Racing = Not very much!

HINT: Running the spacers to index seems to negate 1/2 the gains so we
keep a lot of new plugs in the trailer to sort thru (50 to 100 usually)

 

[mopar 3 B]

I have tried it and put it into the false info file just like the angled pug modification promoted years ago. I do believe the magazines will promote about anything to get people to spend their money. I still remember the early 70's when they were trying to tell everyone chrome would increase HP. Then there was you've got to paint your combustion chambers. Not sure why anyone with a street driven car would even buy into this stuff. Not saying all mods are bad. But common sense needs to be used also.

 

[66Satellite47]

In the early '80's I did try indexing in my drag car, 440 or 400/451. Can't say I saw any difference. However, V notching the electrode seemed to make .01 to .02 ET difference with my MSD 404BC.
Edit: BTW my 440's were a moderate dome and one 400/451 was a high dome, again no real difference.

 

[dvw]

If you need dome clearance it's a must. If not? Not worth the time in most cases.
Doug

 

[493 Mike]

Similar topic-different machine. The SkiDoo snowmobile direct injected two stroke engines come with indexed plugs and OEM replacements are designed exactly like the factory plugs to provide the correct indexing. 850 cc makes 165 horsepower.
Mike

 

[Darter6]

only to discover that the spark plug didn’t really care.

If you don't have a 14 to 1 engine, I wouldn't bother.....

I am lucky when I find a Hundred by indexing!

I agree with John on the last one. When you race a Stocker you do everything you can to get the most out of your engine.
Other than that, read the top two.

 

[66Satellite47]

Similar topic-different machine. The SkiDoo snowmobile direct injected two stroke engines come with indexed plugs and OEM replacements are designed exactly like the factory plugs to provide the correct indexing. 850 cc makes 165 horsepower.
Mike

493, that is one hell of jump, 2 cycle injected snowmobile compared to a 4 cycle V8. What does your timeslips tell you?

 

[INTMD8]

Similar topic-different machine. The SkiDoo snowmobile direct injected two stroke engines come with indexed plugs and OEM replacements are designed exactly like the factory plugs to provide the correct indexing. 850 cc makes 165 horsepower.
Mike

Yes. Mercedes DI engines require this as well.

https://techtips.alleuro.com/wp-content/uploads/2020/02/mercedes-spark-plug-index.pdf

 

[493 Mike]

Yes. Mercedes DI engines require this as well.

https://techtips.alleuro.com/wp-content/uploads/2020/02/mercedes-spark-plug-index.pdf

Aha!
Mike

 

[Endangered Species]

We did it on the 410 Sprint motor ONLY because of piston to head clearance. I would say that's the only reason to do it.

 

[33 IMP]

We did it on the 410 Sprint motor ONLY because of piston to head clearance. I would say that's the only reason to do it.

NOT saying you aren't absolutely right. That's basically what I said too. But now I'm wondering if it would make a difference on a heavily nitroused motor, considering that they don't like extended tip plugs?