Indexing Spark Plugs.

[PHANTMXR6]

My thoughts exactly. Can't do any harm so why not give it a go.

The position of the plug you referred to on a 4valve motor is exactly the position I was talking about and will be aiming at fitting them that way.

I reckon for about $100 I should be able to get a set of NGK BKR6EIX-9 plugs and a shim kit to do the job.

Looking forward to doing it and seeing the outcomes.

[BFHOON]

the theory is that having the cut out of the electrode facing the exhaust valve the spark is shielded from being blown out by boost enerting from the inlet valve.

this could work as we all have to set out plug gaps to 0.79 to stop spark blow out.

in pervious motors I ihave built mostly single cam turbo single coil spark setups I found using a high energy coil discharge kit like jacobs or a crane cams hi6 al does the job also.

I have seen a jacobs coil and jacobs discharge box combo`s throw a spark 1 foot long from the lead to the block.

has anyone seen a discharge box for multi coil cars like ours, I have been looking around but have had no luck.

[howitzer85]

I'm having trouble understanding this.... how can the plug being pointed at or shielded from the inlet valves have any benefit???

remember that the valves are well and truely closed at the time of ignition and the mixture has been compressed...

how can boost entering the valve blow the spark out? (unless your running some wizz bang ignition system that ignites on the inlet stroke?

[PHANTMXR6]

It's probably best if you Google 'benefits of indexing spark plugs' and have a look around.

Might make more sense once you've done a bit of research.

[howitzer85]

For those that don't know what indexing is, it is shimming the spark plugs so that the electrodes all face in the same position.

Straight at the inlet valves.

What Is Indexing?

Generally speaking, the idea of indexing is to position the spark plug so that its gap is facing the center of the cylinder, angled slightly toward the exhaust valve—the most common arrangement. (Some engines work better with other gap locations.) This is important because, as the piston approaches TDC, the air/fuel charge is being compressed. The charge or "mixture" is being forced toward the area of the spark plug—and normally, the exhaust valve. The true speed of this force inside the combustion chamber is extremely fast. Some experts speculate that it surpasses supersonic speeds.

Because of this, the spark generated from the plug should be in a "position" to create the best possible flame front. Looking at a typical side-gap spark plug, you'll note that the electrode can actually block the flame process. On the other hand, if the electrode gap faces the on-rushing air/fuel charge, it stands a much better chance of igniting a flame front.

Well that does make sense only I think the biggest gains would be from doing it to old low tech engines rather then the new high tech barra...

but by all means try it I'd be keen to see the gains (if any), altho you mite need to do a bit more reseerch yourself because if you point the plugs at the inlet you'll actually be going backwards (based on the above description...

[PHANTMXR6]

but by all means try it I'd be keen to see the gains (if any), altho you mite need to do a bit more reseerch yourself because if you point the plugs at the inlet you'll actually be going backwards (based on the above description...

On the contrary. If you READ the description and what I wrote you will see I stated facing the electrode at the inlet valves therefore the gap would be facing the exhaust valves.

With the new head design of the FG and the slightly shielded inlet valves this would inturn cause the compressed charge to head towards the exhaust valve side of the head.

But it's good to hear you now understand the concept.

[PHANTMXR6]

First of all, I'd like to apologise to all the people that I may have confused or misguided.

I've just realised that in my posts the 'electrode' I have been referring to is the 'ground electrode' and not the 'centre electrode'.

I should have made this clear from the start.

http://i702.photobucket.com/albums/ww30/PH...lug_anatomy.jpg

[Dagabond]

With the new head design of the FG and the slightly shielded inlet valves this would inturn cause the compressed charge to head towards the exhaust valve side of the head.

Shape of the piston head would negate this...the combustion chamber would be optimized to have the igniting gasses directly in the center of the chamber not off to one side pushing against the side wall of the bore.......

[PHANTMXR6]

I've not seen the piston design in the FG engine.

I have seen the head though and from the looks of it gases would definately be heading in the direction of the exhaust valves.

Anyone got a pic of an FG T piston?

[senna_T]

Pretty sure they still look like this, but with a little more dish (ignore the valve marks, they came out of an engine that was out of time)