Spark plug Modification

Seriously..... I have been thinking about the benefits and risks of cutting back the ground electrode on your standard J-Gap spark plug.

Now retracting the GE(ground electrode) to redirect the path of the spark off to the side and exposing it more tword the fuel charge would improve HP, and fuel economy; or even reduce timing, while keeping the gap distance relitively the same.

Now, possible bads are a problem with pre-ignition because of over heating of the ground electrode or reduced life span of the spark plug.

But i don't see this as such... now by cutting back the ground electrode people would think that well there is going to be sharp corners on the end which would over heat and cause pre-ignition but any smart person would understand that you should smooth the rough edges to reduce this risk... i even belive that the shorter GE would have a lower chance of over heating than that of the unretracted J-Gap plug because of the reduce surface area for heat to be absorbed and the distance the heat would have to travel in order to dissapate the heat collect on the GE because of its reduced length..

A friend of mine who's a motor head and a mechanic say that by retracting the GE to expose more of the spark would damage/destroy the pistion(Aluminum) because of the intense heat of the spark:eek:, is this true, what would the likely hood of something this extreme happening to a v8 smog dog with low compression and stock ignition system?

I'm not considering any fancy platinum or iridium high temp spark plugs, more like inexpensive stuff.

I really want a good definitive answer... experence with this, websites, anything you can give me so i can understand this situation, and mabey clarify some things about this so nobody who run across this "neat trick" doesn't get a nasty surprise.

A few things:
1. Your friend is wrong about the 'intense heat of the spark' destroying the piston. The flame front and temperatures generated by burining fuel are much greater than the spark energy. If the piston can survive being exposed to the burning fuel, the spark is like nothing by comparison. I have received plenty of shocks from spark plugs over the years. The spark does not feel hot at all. (painful, yes, hot no)
2. Filing the sharp edges off the electrode actually harms the ability for the spark to jump. Do not do this.
The spark is propegated or helped to jump by the sharp edges on the electrode. There are plugs out there that have tried to exploit this principle, like the NGK U-Groove, the Splitfire plug, (and another, maybe NGK, maybe Delco) which uses a fluted ground electrode with lots of sharp edges.
Rounding off the edges mimics the wear and decreased peformance than you get from a worn out plug. Have you ever seen a plug with 50,000 miles on it? The sharp edges on the electrodes are eroded away, which is one reason why worn plugs don't work as well.

Racers have been 'sidegapping' plugs for years with good results. This is when you just move the J-electrode to the side a bit, but NOT shorten it. This exposes more of the ground electrode to the fuel-air mixture for better burning, and exposes two sharp edges of the two electrodes directly facing each other for easier spark propegation.

PLugs are not designed this way because they wear faster, and lose efficiency faster, as the sharp edges become eroded. However, as far as I can see, if the side gapped plug just lasts 10,000 miles before losing efficiency, its still worth the power gains you would get.

The highest performing of the racing engines have used surface gap plugs since the eighties rather than J-gap plugs. Even if those plugs are less efficient than J-gaps they can survive in the environment of a racing engine, even U-gaps don't hold up.

A spark plug have a certain temperature which must be kept when the engine is running. This is controlled with the heat trensfer from the plug to the head. Overheat = pre ignition, too cold = it cannot longer clean itself.

By using electrode materials like platinum and iridium it allow the electrode to be made smaller, but it also increase the life of the plug. This can not be done with normal electrode materials. Even if the plugs are expensive to buy they last so long that they are actually cheaper in the long run.

Also ut should be noted that any gain by a plug is too small to even notice on a dyno.

What effects would there be to the heat range of the spark plug if the electrod was cut back... would it remain the same?

I wanna get as many knowledgeable responces as possible, I like to tinker even if it doesn't make much difference, but i also don't want to break stuff.

The heat range would remain the same, since you are not shortening the center electrode.
The heat range is dependant on how long the center electrode is, (relative to the metal body of the plug) and its material (copper core plugs (some NGK) dissipate heat faster than the iron core, and thus have a colder heat range than the iron core, all other factors being equal.)

http://www.georgenitta.com/autotipssparkplugs.htm

I've done up my spark plugs according to this website, and also informed 2 friends about it, all 3 of us got slight improvements.

I try to make the edges pointed but not too sharp to prevent detonation, i.e. I file off the edges lightly.

The downside to this mod is that the spark will concentrate on a smaller surface and therefore wear will be faster compared to the original larger surface to spread out the wear.

Make sure u have a feeler gauge to measure the gap b4 starting this mod! I'm now running 1.3 to 1.4 mm (OE gap is 1.1mm) as I don't need a small gap for hi rpm.

So what's the shortcomings of surface gap spark plugs apart from the higher price?

I've come across an article about F1 plugs, and the engineer interviewed said they use surface gap plugs only because of the space savings (due to them having no ground electrodes) and its performance is not that good.

So what's the shortcomings of surface gap spark plugs apart from the higher price?

I've come across an article about F1 plugs, and the engineer interviewed said they use surface gap plugs only because of the space savings (due to them having no ground electrodes) and its performance is not that good.
The main reason is that the J-gap electrods would break in a F1 engine but there are also space issues.