Spark plug topic Heat, Gapping, Indexing and etc.

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Things I've read but havent had the time to try it on my turd. Its a rule of thumb for every 100 HP you go one step colder and the bigger the gap the better, but with boosted cars it can blow out too much of a gap. (???) I've been running BKR7-11 NGK V-power for a while now with a .30 gap and i was fouling out plugs after 10K miles. So i figured the Iridium would help and so did the shops around here and hey guess what everyone is wrong. Im contemplating going even colder to a BKR8-11 or indexing the plug but I've never really payed attention to the direction of the plug gap. Now I must have over read the story on gapping i pulled this from NGK website...
Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.

A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.

With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think (pulled from: http://www.ngksparkplugs.com/techinf...stallation.asp.

I'm looking for more success stories so i can figure out my plug problems and help out others with this constant question. Monstah said once that the stock Ignition system can handle upwards of 400WHP IIRC. I know one thing im dumping the Iridium unless I'm using them improperly.

[DriftPunk]

Things I've read but havent had the time to try it on my turd. Its a rule of thumb for every 100 HP you go one step colder and the bigger the gap the better, but with boosted cars it can blow out too much of a gap. (???) I've been running BKR7-11 NGK V-power for a while now with a .30 gap and i was fouling out plugs after 10K miles. So i figured the Iridium would help and so did the shops around here and hey guess what everyone is wrong. Im contemplating going even colder to a BKR8-11 or indexing the plug but I've never really payed attention to the direction of the plug gap. Now I must have over read the story on gapping i pulled this from NGK website...
Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.

A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.

With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think (pulled from: http://www.ngksparkplugs.com/techinf...stallation.asp.

I'm looking for more success stories so i can figure out my plug problems and help out others with this constant question. Monstah said once that the stock Ignition system can handle upwards of 400WHP IIRC. I know one thing im dumping the Iridium unless I'm using them improperly.

1.) Go back to copper plugs (the NGK V-Power Coppers)
2.) If you have bumped compression go with 0.030"-0.035" gap. (If you are boosting, definitely go with 0.030")
3.) You want to go HOTTER plug if you are fouling them out. Hotter will burn off the deposits (If you are fouling the current ones out, you are running too cold of a plug).
4.) You do not want platinum or iridium plugs on a wasted spark ignition system.

You could try this plug (with 0.030" gap): http://shop.advanceautoparts.com/web...093-P_N3411I_P hottest plug I could find. Heat range 11, lol.

In all seriousness, a heat range 9 V-Power Copper NGK, gapped at 0.035" should suffice, if you are fouling out a heat range 7 NGK copper gapped at 0.030".
The heat range 11 is probably too hot for a boosted application. It could be that 0.030" gap is too small and not burning the fuel mixture completely, leaving fuel deposits on the plug, turning into carbon, and fouling them out early.
Another thing you could try is running a fuel system cleaner, like Seafoam or Gumout All-in-One, every 3-4 fill-ups (about every 30-35 gallons) to keep deposits from building up, and make the plugs last longer.

Just some stuff to think about.

[S.Bretz]

Unfortunately, if you want to make big power, you need to the colder plug. And since 99% of the time you are not flogging on the gas pedal and makeing 20 pounds boost to take advantage of the colder heat range, the plug fouls out. The Irdiums have laster longer on me engines...and Jay's too before they foul out. Expect to replaced them ever 3 monthes.


The heat range 7's should be good up to about 300-325whp. After that, you should really consider puting in a set of 8's. I range 7's for years and they where great until the dyno when I was turn the boost past 20psi....the igntion would break up and it lost power. I added fuel, pulled timeing...nothing. Put the 8's in and jumped up 40whp. Pulled the fuel back out and added timing back in and picked up another 60-70whp.

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Unfortunately, if you want to make big power, you need to the colder plug. And since 99% of the time you are not flogging on the gas pedal and makeing 20 pounds boost to take advantage of the colder heat range, the plug fouls out. The Irdiums have laster longer on me engines...and Jay's too before they foul out. Expect to replaced them ever 3 monthes.


The heat range 7's should be good up to about 300-325whp. After that, you should really consider puting in a set of 8's. I range 7's for years and they where great until the dyno when I was turn the boost past 20psi....the igntion would break up and it lost power. I added fuel, pulled timeing...nothing. Put the 8's in and jumped up 40whp. Pulled the fuel back out and added timing back in and picked up another 60-70whp.

Great Sam, i figured fouling them out was a part of life. How about plug gap should i start at .25 and make them bigger until the spark no longer blows out? IMO iridium's are to expensive to be fouling out that much. I'll have to work the corner with a sign that says hand jobs for spark plugs lol.
Which way do you point your plug gap too exhaust or intake side. Well I'm going to play with it today and see what comes out of indexing the plus and going to 8's.

Drift-the higher the number the cooler the plug. 11 is extremely cold and 5's are stock but thanks for the info.

[DriftPunk]

Drift-the higher the number the cooler the plug. 11 is extremely cold and 5's are stock but thanks for the info.

LOL. Whoops. Oh well, at least I gave some good info. My bad.
Also, face gap toward exhaust if you are going to play with that. Not sure if it will make a dif, but facing the exhaust will push the flame front toward the exhaust valves instinctively, so it should have a better flow path.

[S.Bretz]

Only on NGK's do the higher numbers mean colder. Every other plug manufacture, the higher the number, the hotter. NGK has to be backwards for some reason.


I never index the plugs. Its a waste of time. I don't gap them anymore either. The 8EIX's come out of the box at .032 ever time. When I run the 7's (i used to put them in on when I knew I was going on trips), they came out of the box at .040. The ford edis system recommened a gap of .060 on the escorts, so I figured at .032/.040 they where already down from what that should have been.


Some people would dissagree with me, but the way I figure, if you have to drop the gap under .028, then you need a stronger coil. Running it down to .020 or .025 to me seems too small. Technically, you want the largest gap you can get so the plasma arch has more of a chance of starting off the combustion...with small arch, yeah, you can get the spark to jump the gap with a weaker ignition system, but, you just reduced your chances of having a fuel molecule and an o2 next to each other near the heat of the plasma arch to start the reaction...if they three are not there (air/fuel/spark) in that tiny gap, you still get a misfire. A bigger gap is like buying more lotto tickets....the stock coils are very strong. You shouldn't have an issue running .040 gap up to about 15psi. You can probably push it, but over that (say up to 25 psi) it would be a good idea to drop the gap to .035 to .030 (.o32 should be good to about 30psi as i have run that before in short bursts).

[TheMU47]

I use ngk 7's for daily driving. this last set has been in there a year or so. the gap I use is .035". for the dyno, I use ngk iridium 8's.