INDEXING A PLUG MythBusters

[Bryan Raffa]

:idea: HOW'S IT DONE? I have try-ed different plugs, and indexed the electrode with a sharpie marker .. witch I see now you can not go by the letters for indexing as they are all different ,


whats the secrete to starting the plug the end up pointing at the exhaust port,,or is it the intake thats more in-tune to making HP.. spill the secrets guys!!! or is it all a farce ..:lol:

I have starting the plug at 15 degrees 30,45.. all using the open part of the electrode to face directly at the exhaust.....come on HP secrete robbers!:)


or must I start with a brand new Plug , got it...:crazy: for the finger snung tight,1/8- 1/4 turn .. whats the myth.

[Mrs.Mosh]

It works.
Mosh did it in his drag car.
He bought 3 sets of plugs, and indexed them towards the exhaust valve. Trial and error, with paint like you did.
They say it burns off the fuel more complete.
They make index washers for the cars.
Probably make them for ATV's too.

[Bryan Raffa]

what you mean willis? washers? huh ... theres gotta be a trick.. I got lazy after a few hours and a bunch of plugs..:wondering


Anyone Else?

[Mosh]

What she said.There are washer kits avaiulable for cars that help you index them.

I have never looked into the bike plugs though.

http://dodgeram.org/tech/gas/spark_plugs/s_plug%20_indexing.htm

[outtaline]

be very careful indexing 2 stroke and yes point it at the intake washers are available through any hot rod parts supplier and some auto parts stores

[Bryan Raffa]

ahh mosh cool reading ..angle of the hole has alot to do with it ..wild.. going to look into this deeper. I was pretty mutch on the right track with the marker..

[HondaHarry]

It works. Used to do it on my drag car and street car. (Aircooled VW's)
Made the exhaust note change just a touch too. I think it sounded way better.
you could just tell by the sound it was more efficient. Kinda like when an
engine purrs when you have the fuel mixture perfect, vs close. I think
I bought the index washer kit from Summit Racing. Man that was a long time ago. HH

[200x Basket]

i am not sure how much effect it would have on a bike. on a car you index it so the opening is pointed to the top of the piston. on most two strokes the plug is nearly straight up and down.

as mentioned you use washers to do it.

[Bryan Raffa]

a washer would raise it(plug) too high in the head right?... at least on a 2 stroke did you guys have to buy longer plugs? Lotta variables here... keep the input comein,,,,

[Billy Golightly]

Well, hypothetically, the thickest the washer would need to be, would be the thickness of the threads for one turn (which isn't very thick) Probably like 1-1.5mm tops. You could probably do it by stacking some pieces of brass shim stock up, as thats how I've heard of it being done before.


I don't know much about this, the only other thing I can add is that keep in mind, the closer the plug is to the piston, the more chances of detonation your going to get. But also the more recessed and shielded the plug is, the less clean and efficient burn your going to get.

[3Razors]

Indexing a plug on a 2 stroke doesn't produce any benefits. The explosion happens inside the dome. The fuel entering and exhaust exiting happen farther down the cylinder walls so it makes no difference which way the electrode is pointing.

[MyMistress86R]

As far as clearance is concerned...based on what has been said by billy and others...you might want to test/practice this with just the head so you can see where the plug will finish in the dome when tightened. That way, you can determine if you need shallower or deeper plug tolerances. I have zero informed input on the subject, but the test process just seems logical to me.

[cr480r]

Indexing a plug on a 2 stroke doesn't produce any benefits. The explosion happens inside the dome. The fuel entering and exhaust exiting happen farther down the cylinder walls so it makes no difference which way the electrode is pointing.

I completely agree.. its a 4-stroke thang...

[Mosh]

True it has always been a 4 stroke application.

Speaking in theory, it may add a benefit on a 2 stroke.

In cars I was always told to index the electrode facing the exhaust valve (On a small Block Chevy). This helps get a total burn as the mixture ignited from the intake valve or center of the piston, and swirled out the exhaust valve.

So in theory, all firing sequences or "burns" are just that if tuned correct.
A swirling controlled burn (not explosion) that ignites usually from the center of the piston and burns in a circular pattern, over to the exhaust side.
Therefore indexing the plug on a 2 stroke towards the exhaust port, may actually offer a more complete burn as well.
I have no evidence or testing this in a 2 stroke, but I dont see where it would hurt anything either.

[Bryan Raffa]

this is what started me on the whole thing . see how the carbon build up is on the front of dome.. exhaust side..on this cylinder. and in all theory as soon as it explodes in the cylinder/IE..dome the next step is out the exhaust.. why not point the explosion twards the exhaust.. this motor has not been opend in over 10 years. Ran like a swiss watch

you can see by the carbon the explosion starts in the dome like razor said,, but then creeps out twards the exhaust..

[cr480r]

I think that build up you see is because the exhaust side of the dome doesnt get "washed" by the incoming unburned charge.. since the burn begins so close to tdc and is packed tightly into the dome with a centered plug.. I doubt mixture cares what side of the dome the spark starts on...

[Dirtcrasher]

Billy hits on the size well.

I had to do something like this with machine handles .... If the lever tightened and stopped at 7:00 instead of 12:00 I had to figure out how much material to remove from and or shim the handle to get it dead nuts.

If it's 1MM between threads then .25MM changes the index 90 degrees, .50MM changes it 180 degrees. From there you can figure out everything inbetween. Hope I'm saying that right, haven't been machining regularly for a few years now :D

McMaster has these thin SS washers for "aircraft/military spec" and they may be just what you need.

I just wonder about air leaking because you would no longer have direct contact to the head unless you remove the stock plug gasket, slip on the washer and then the gasket......

Possibly a bag of .005 washers could be played with to get the index you want.

[Yamahondaman]

i used to make em from .005 to .015 .. i would make so the open tip was towards the exhaust as if you looked at a 2-cycle head ... the "dark" area is towards the exhaust...Better spark burns the gases better ... i havn't done it in awile and i havn't made them for some time as the "secret" from the "MANTIS" Power leak's abit more ? :naughty:

[Bryan Raffa]

Problem is.... that all pugs are diffrent .. I have a B9,B8,B7 and the threds start in diffrent spots..

[outtaline]

Hey Bryan its not just different style plugs not all b9 b8 b7 plugs start in the same place 4 b9 plugs might start in 4 different places to index plugs on my old kz 1000 inline 4 for those that don't know it took 5 or 6 boxes of plugs 9:1 compression and 14lbs of boost they had to be almost perfect or it would eat a piston in a night of bar hopping I didn't use washers I worked at a bike shop and our bikes were our advertising the right way to do it is without washers its just expensive and it is very time consuming I am not sure of the benefits with a 2 stroke but on 4 strokes if they are road had they should be indexed even if they are stock

[Black86tri-z]

dont mean to change subjects but while talking bout plugs they also cut the electroid back a little to make some power

[Tecate 50]

Why are you indexing? I used to idex my plugs on my dragrace motor to clearance the dome for better flame travel due to nitrous and fuel be added in the cylinder! There are no benefits to indexing a two-stroke!

[Tecate250]

Ok for us dumb heads what do you mean by Indexing plugs? Is it lineing up the open end of the electrode twords the exhaust "Valve"? Are you trying this with a 2 stroke to have better "flow"? Not really sure about this but non the less if it adds hp then Im in :)