v8

iTrader: (10)

well people allways say that the closer the gap the colder the plug, but the closer the gap the hotter the spark would be? If its too far apart the spark would be weak?
The reason I ask is the 03 and up gap is at .40 and the 99-02 is .60.

can someone clear this up?

jmproductions

That's interesting because according to NGK, who makes our OEM plugs, the 03-05 trucks use the same plug and gap as my 2001: NGK PZTR5A-15 @.060

Where did you get the .040 info because I think I've heard that before?

v8

iTrader: (10)

well I have a 04 suburban and the neighbor has 04 ecsb truck and both owners manual says the plug gap is .40 and on all the 99-02 i've seen is .60, well when you go to the part store to get plugs the a/c delco ones they say not to regap the plugs and they come pre set at .40

bluecajun5.3

iTrader: (31)

humm, do you have your stock airbox? it might say it on the white sticker. mine's back in LA. so i couln't look at it.

stone150

iTrader: (2)

mine says .6 but i have herd on this site or others that if you buy ngk's or stockers even though they are not .6, you are not suposed to regap, it makes the truck worse when you gap to .6

Yelo

I run at .060 and have to replace plugs quite often (every 10-15,000 miles), next swap I'm gonna try .045 to see if it quits fouling them

v8

iTrader: (10)

there is a sticker on the front of my truck and it says to run .60, But my question still is the closer the gap the colder the spark? and why is that?

hog

I would think that the closer the gap the colder the spark is a true statement

Electricity is simply the movement of electrons. In order for electrons to pass from 1 atom or molecule to another, the particle must be ionized, or give up or accept 1 or more electrons leaving the particle with a positive or negative charge and NOT neutral like they prefer to be. It takes a finite amount of energy to be able to ionize any particle.

If you have a 0.060" gap there are more actual molecules between the positive and negative parts of the plug (anode, cathode) that there is in a 0.030" gap. Having more molecules between the electrodes means you will need more electricity to be able to ionize enough molcules for the spark to jump the gap.
The more compression, be it by static compression(ie 9.0:1), or boost(turbo supercharger) or chemically(ie NO2) an engine has the harder it is for a spark to jump the spark gap. All of the things listed above are means of raising combustion pressure, (therefore pushing harder on thepiston for more power), increase the number of air/fuel atoms and molecules that are present between the 2 electrodes.
Since it takes a certain amount of electrical energy to excite these particles enough for them to give off their electrons, the gap cannot be too large. Or in other words there cannot be TOO many particles in between the electrodes or the spark cannot jump the gap. This explain why when using power adders on an engine requires either smaller plug gaps and/or a higher output coil.
So TOO many particles between the electrodes with not enough voltage and the spark wont jump the gap.
You apply the power from the coil to the plug gaps, as the electricity travels from the cathode to the anode(or vice-versa?) it must pass thru the a/f particles, each particles energy level or level of excitation rises, when its at its highest it kicks off an electron to the next particle, this electron makes the next particle excited as well so it kicks off an electron to regain stability, this goes on until the spark reaches the other electrode. As the particles regain their stability after kicking its extra electron to its neighbour, the particle relases energy in the form of heat and light(thermal,& radiation). It is this heat which starts the burning of the fuel and air mix and forms a kernel around the spark gap and then the flame front travels outwards combusting fuel along the way. The more complete and hotter the burn, the higher the cylinder pressure spike and the less unburned fuel is left over then gives you the most power with the least amount of polluntants possible.

If you have TOO small of a gap, not enough molecules of air and fuel will be exposed to the spark to continue the flame front to all parts of the chamber and an incomplete combustion of the a/f charge will result. I beleive the area around the sparkgap which is ignited first by the spark is called the flame kernel, the flame kernel then ignites other a/f particles and the burn continues to the rest of the chamber. As the flame front covers the entire chamber, the cylinder pressure rises quickly and pushes the piston down.

Its a balancing act with plug gaps, too large, the spark wont jump, too small, you get a poor flame kernel then a poor flame front and then poor rise in cylinder pressure which means poor power.

I think that if you could measure the actual temperature of the spark and compared a plug gap of 0.060" and 0.030", you would find that the large gap would be highest simply because there are more particles being excited into instability, then releasing heat and light as the particles return to their stable original forms.

I hope this kinda makes sense, its been a while since I have studied Chemistry.
Sorry for the book.

peace
Hog

jmproductions

What is the actual Delco plug number that you bought? My OEM plugs said AC Delco & NGK TR5 on them. So I figured NGK made them for Delco and their site seems to support this but their number is PZTR5A-15. This is the same plug number for all of the years according to them. All I know is that I have the copper (NGK TR-55) plugs @ .050 in it now and I think it ran better with the OEM plugs @ .060. So I'm going back to those despite the fact that they cost $10 a plug!

That's some good info HOG, thanks! So if I follow him correctly GM may have changed to lower energy, possibly cheaper, coils in 2003. Then they would need to decrease the gap to compensate. Anyone want to research this or know offhand?

v8

iTrader: (10)

thanks hog lol, and very nice book you wrote. The ones I bought were the ACDELCO Irridium plugs, on the box they say gap them at your vehicles spec, but the guy behind the conter showed me in bold letters not to change gap lol, well I set the gap on them at 55 today. I will see if my seat-o-meter can feel the difference lol, I dought it but it makes sense what hog said. I know alittle about elect.

I can take a megger and have it set to 15kv and it will make a small spark about 1" away but at a 1/4" away it will make a very bright spark and crackle. That was why I was asking the question. thanks for the help.