Plug Indexing?

[John76]

After seeing Majdomo's E12 head (see latest post in Wallace), I was curious to know if anyone indexes their spark plugs.

Seems like cylinder 1 spark plug position would work better than cylinder 2, where the electrode is shielding the intake charge. 

Any value to this?

 

 

[Hans]

I doubt you'd notice any difference but no harm in experimenting while the head is off.. More of a "blueprinting" procedure.

[jimk]

If it is not known what is best, how are you going to know what to index the plugs to?  I can't see what difference it makes. Any spark in a combustible mixture will set the burn started.

[gary32]

Blocking injector spray in a direct port injection system like my 2 stroke Evinrude etec outboards or maybe really hi boost situations are the only applications I know of for indexing.

But I like the #1 electrode position also, why not give it a try.

 

Worst super bowl ever?

Edited February 8, 2021 by gary32

[Son of Marty]

Plug indexing made some sense with the low power ignition systems back in the day, but now with the electronic and msd type of systems not so much. Back when I was building engines for race boats for at least, champion plugs, you'd need to specify a cx prefix plug to have the plug body threads and electrode clocked into the same position on each plug, I don't know about most plug makers do today but I don't think they are clocking the plug and if the plugs not right you'd have to pull the head every time to clock the plugs.

Edited February 8, 2021 by Son of Marty

[uai]

I am running plugs with 4 electrodes anyway.
But in general I think there are way better opportunities to improve an engine

[John76]

10 hours ago, uai said:

But in general I think there are way better opportunities to improve an engine

Absolutely...just looking for any little thing that can easily be done for only the cost of a shim washer.

No need to disassemble anything. Just mark where the electrode is on your spark plug wrench and torque until it is facing away from the intake valve.

Might give you the same performance increase as filling your tires with helium....lighter = faster!

[Schnellvintage]

Based on the color of the spark plugs and combustion chambers, I'd be more concerned with the correct mixtures on and off idle throughout the RPM range.  Looks very lean....form what I see.

[Preyupy]

I have tried indexing plugs, projected tip and non, and even surface gap plugs and have not seen a repeatable difference on the dyno.  This on lightly modified 125-150HP street engines as well as 200-225hp race engines. I have tried a couple of piston dome designs over the years that have been so close to the plugs that I could not run a projected tip plugs (neither of these turned out to be very good designs)  

 

I think there are engines where the plug is so far offset in the combustion chamber that indexing the plugs can make a difference (early GM and Ford V8's being a couple of examples) but the position of the plug in the combustion chamber in the M10/M30 engines makes this a moot point. 

 

I suspect that on an engine that has a mixture problem or an oil consumption issue the plugs MIGHT stay cleaner longer or be less prone to misfire but I have not data to prove this one way or the other (just my WAG)   

[Hans]

1 hour ago, Preyupy said:

I have tried indexing plugs, projected tip and non, and even surface gap plugs and have not seen a repeatable difference on the dyno.  This on lightly modified 125-150HP street engines as well as 200-225hp race engines. I have tried a couple of piston dome designs over the years that have been so close to the plugs that I could not run a projected tip plugs (neither of these turned out to be very good designs)  

 

I think there are engines where the plug is so far offset in the combustion chamber that indexing the plugs can make a difference (early GM and Ford V8's being a couple of examples) but the position of the plug in the combustion chamber in the M10/M30 engines makes this a moot point. 

 

I suspect that on an engine that has a mixture problem or an oil consumption issue the plugs MIGHT stay cleaner longer or be less prone to misfire but I have not data to prove this one way or the other (just my WAG)   

I read about in my small block Ford days.

[TobyB]

Yeah, most of the indexing that seems to matter is on very high- dome split- chamber head designs where

there are bad places to put the electrode ground tab, as it may shroud the spray from a Hawley Dubble Pumper.

 

The 2002 heads are all pretty good- I did make an effort to keep the tab on the exhaust side and closer to the 

roof, but like Byron, I could not find any tangible benefit other than it made me feel like I was 'trying really hard.'

 

Now, the holes in the head sealing surface, that might affect compression a bit...

 

jus' gessin.

 

 

t