Spark plug gap - simple discussion

[cam98aro]

Re: Spark plug gap - simple discussion

Noted. The other plugs are a breeze to swap out.

i was able to change all of my plugs with a u-joint, or swiveljoint, extensions, and a regular spark plug socket with an open ended wrench to fit it

they also sell very small spark plug sockets that are completely hollow so the plug can go through the socket and give you a ton more room

[Abaddon]

Re: Spark plug gap - simple discussion

Where were you 4 spark plugs ago?! :)

[Abaddon]

Re: Spark plug gap - simple discussion

The car purrs like a kitten. I used the NGK TR6 4177 plugs with Exxcel 8mm wires (because they have 90 degree bends in both ends and the engine side is coated for high temps and won't melt) and gapped the plugs to .055 and it runs like a Swiss watch! I haven't gotten used to the throaty sound of the Pacesetter headers, 3" Magnaflow dual exhaust, and 3" Magnaflow hi-flo cat but otherwise, very impressive!

[Hib Halverson]

Re: Spark plug gap - simple discussion

Spark plugs are actually pretty simple but aftermarket spark plug vendors want to make them seem complicated because, then, they can sell you complicated, and sometimes expensive, "solutions". An example are the Bosch "Platinum" plugs with two and four ground electrodes along with plugs with capacitors inside and so forth.

As for plug gap, simply stated, you want the widest gap your ignition system can consistently fire. The wider the plug gap, the larger the spark that is exposed to cylinder's air/fuel charge, the easier the charge is to ignite. This why plug gaps have gone from about .030 in the 1960s to as much as .070 today. How large that gap can be generally depends on 1) available ignition output energy, 2) wear rate of the plug electrodes and how long the plug will be in service and 3) cylinder pressure.

There were comments above about running less gap for high rpm performance. I would not do that as a rule-of-thumb. If you need to close-up the spark gap to maintain high rpm performance, that's a sign that the ignition system is not capable of firing the charge. In cases of higher cylinder pressure, that might be necessary but a better choice would be to modify the ignition for higher output by reducing resistance on the secondary side with iridium-tipped plugs (ie: Denso, NGK, etc.) or lower resistance plug wires (ie: MSD SuperConductors or similar product) or increasing the stock ign. system's output using "hotter" coils (such as MSD PN 8224). That combination (Iridium plugs, 50-ohm/ft. plug wire and hot coils) works well on normally-aspirated, modified V6s along with those running mild "shots" of nitrous oxide. For turbocharged engines, those running a lot of nitrous oxide and or rpm over 6400, aftermarket ignition modules with higher output maybe be necessary.

"Copper" spark plugs have been around since the mid-70s (NGK was first to introduce that feature) and have a copper center electrode inside the spark plug but the copper does not extend to the part of the center electrode that is exposed to the spark or combustion. If it did, the plug would soon fail because copper is hardly reliable or durable under those conditions. Typically the center electrode tip is some type of exotic nickel/steel alloy, platinum or iridium.

Our V6es which are modified seem to work best on the street with an AC "2" heat range (NGK 6 or Denso 20) and for racing an AC "1" heat range or colder (NGK 7 or 8, Denso 22 or 24). I run Denso IT20s on the street and Denso IT22s for chassis dyno testing, acceleration road testing or race track use. Since the early-'00s, I've used the IT20 on the street and have found them to be astonishingly long-lived in a modified, hi-po street application. If there's a downside of the Densos, it's they are a bit costly. To me, I'm not willing to compromise on that, but others may. Another plug I used early on was the AC 41-919 which is a fairly cold AC double-platinum which was originally stock in Cadillac Northstar 4-cam V8s. Also, the 41-919, at one time, was a popular performance upgrade for 90-95 Corvette ZR-1s which also use a four-cam V8. The 41-919 is sort of between the Denso IT-16 and IT-20 in heat range. The 919 is hard to find these days but I see them at Internet retailers and on eBay sometimes at a cost that is less than iridium-tipped plugs. Lastly, plugs from some of the Gen 3/4 V8s in Corvettes may work well in mod'ed V6es on the street.

As for iridium...it's the best choice for spark plug electrode material because 1) it has durability as good or better than platinum and 2) its resistance is less than platinum, so for a given ignition system, an iridium-tipped plug has more spark energy at the tip. The second part is why OEs, including GM, have moved from platinum-tipped to iridium-tipped plugs.

[Turbo V6 Camaro]

Re: Spark plug gap - simple discussion

I run jegs coils and stock $20 auto zone wires..... i can gap up to .042 at 15 psi and under over that I gap at .038 i have yet to test over 24 psi but i will most likely gap at .035 just to be sure.

I run Tr7 non projected tip for up to 18 psi and Tr8 non-projected tip for 20+ psi

I have tried the IX plugs and noticed no increase or decrease in performance and my gaps stayed the same. For me- not worth the cost when i can replace the copper plug nearly 3 times for the cost of one set of IX's

as already stated RPM is not really a factor but pressure is, the more air that goes in the more that gets compressed the more Resistance there is to the spark arching the gap.

I wouldn't close the gap on an NA car, and running Tr6 NA for a street car you can expect a reduction in life of the plugs the plugs don't get the heat they need to self clean.

Now granted if you have an all out NA car like lances that ran 12.48 NA then yes you need some Tr6 plugs. higher Compression ratio

for a stock motor NA, or even cammed TR55 should be fine...

always check your plugs!!! the only true way to do it is shut the car down at the end of the track and tow it back.............

if you see hot spots on the plug then you can drop down half a heat range (if its there) or one heat range.

[ssms5411]

Re: Spark plug gap - simple discussion

After I took my nitrous off I went back to TR55 plugs and noticed a good difference than running the TR6's N/A , now that I will be boosting here soon I went ahead and put a set of TR6's in again and I really noticed the differnece in running TR55's and TR6's N/A. The car still runs smooth but theres more of a fuel smell out the exhaust running TR6's N/A with no boost. But when I get my new P/P heads in with bigger Manely valves and run more compression also with 1.7 Pro mags, I hope that the TR6's will work better N/A. The TR55's were great but I thought I was installing my turbo sooner but that didn't happen as planned. I also check my plugs before installing and I just leave them as they come TR55's at .055 and TR6's at .035. But it does seem that the NGK's copper plugs run better on our cars than any other plugs. Viper when are you getting your car back to the track and running some 10's?

[Bonemaro]

Re: Spark plug gap - simple discussion

Are you taking the $1.99 a piece TR55's, or the $7 TR55IR's?

[Turbo V6 Camaro]

Re: Spark plug gap - simple discussion

After I took my nitrous off I went back to TR55 plugs and noticed a good difference than running the TR6's N/A , now that I will be boosting here soon I went ahead and put a set of TR6's in again and I really noticed the differnece in running TR55's and TR6's N/A. The car still runs smooth but theres more of a fuel smell out the exhaust running TR6's N/A with no boost. But when I get my new P/P heads in with bigger Manely valves and run more compression also with 1.7 Pro mags, I hope that the TR6's will work better N/A. The TR55's were great but I thought I was installing my turbo sooner but that didn't happen as planned. I also check my plugs before installing and I just leave them as they come TR55's at .055 and TR6's at .035. But it does seem that the NGK's copper plugs run better on our cars than any other plugs. Viper when are you getting your car back to the track and running some 10's?

shotting for fall, get the money gathered

[ssms5411]

Re: Spark plug gap - simple discussion

Are you taking the $1.99 a piece TR55's, or the $7 TR55IR's?

I only use copper ones, $1.99 or less.

[Bonemaro]

Re: Spark plug gap - simple discussion

Are the TR55's the "copper ones"?

[Hib Halverson]

Re: Spark plug gap - simple discussion

First, let me say that the NGK 55 heat range is a pretty hot plug for a modified engine and likely is too hot for an engine with nitrous oxide.

For a mod'ed V6, nitrous or no nitrous, the TR6 ought to be your starting point and you may find an NGK 7 heat range plug will work better, especially if you are racing. In fact, if you're racing with nitrous oxide or turbocharging, you may even want an 8.