Spark Plug info for pushrod motors.

[IsaacHayes]

It seems that GM has changed AC Delco part numbers over the years of the gen2 and gen3 pushrod motors. Use this as a guide for what to run in your motor.

You could run the plug for your year, or try the latest and greatest probably without problems.

I have not been able to find out what changed between the newer platinums and iridiums, but GM switched to those part numbers so I'm guessing they are better in some regard. GM had normal plugs, then went to platinum, and now iridium.

GEN 2:
GEN 3:

It's your choice to run whatever. Normal plugs to save cash, or Platinum/Iridiums for long lasting. It would seem the 41-101 Iridium in the 3x00's is the newest and best for the gen 3.

Main thing is to run AC Delco's because you know they will work. Other brands the heat range and other things may not match up. Also all the AC Delcos listed are double platinum, which is a must with the GM ignition.

A rule of thumb when to replace your spark plugs is typically after 100,000 miles for Platinum and Iridium, and for normal plugs 10,000-30,000 miles or after a year or two. It can vary on your driving style, driving conditions, and as well as the health of the engine systems.

Below is an informative link from AC Delco on spark plug part number decoding:

http://www.acdelco.com/parts/sparkplugs/identification.jsp

[SappySE107]

Iridium plugs are self cleaning and take less power to fire, so they act like a hotter coil is used.

[SappySE107]

http://www.ngksparkplugs.com/techinfo/spark_plugs/techtips.asp?nav=31000&country=US

Good information on selecting plugs and checking.

[IsaacHayes]

Iridium may reach self cleaning temps faster and resist wear more, but I don't see how they take less power to fire. The voltage to arc is dependent on gap and pressure inside the combustion chamber. Not the electrode size or material. I believe that is marketing hype. Maybe their reasoning to claim that is because if they wear less, then the gap stays the same and thus less voltage is needed throughout the life of the plug vs a plug that will wear and the gap gets larger.

I would buy them for long life benefits (resistance to wear and quicker self cleaning temps) but I'm not sold that they make a hotter/stronger spark over any other plug in good working specifications.

I thought about going with them, but they are 3.5x the cost of normal plugs, and I don't even know if my motor will last that long to see that many plug changes. If I had a newer car that just turned 100,000 or so, I would probably throw them in and then not have to think about them for another 100,000 or so.

The platinum is only $1 less than the Iridium so if you are going anything other than normal plug, go for the Iridium.

Prices from http://www.oreillyauto.com/

[SappySE107]

Ill test out the iridium comparison with my scooter. I have the same plug/temp range in regular NGK and Iridum IX. Both plugs have less than 50 miles on them.

I will also try to find some information on the iridium plugs.

[discostu]

Copied from wikipedia, this is why a smaller electrode is better:

The center electrode is usually the one designed to eject the electrons (the cathode) because it is the hottest (normally) part of the plug; it is easier to emit electrons from a hot surface, because of the same physical laws that increase emissions of vapor from hot surfaces (see Thermionic emission). In addition, electrons are emitted where the electrical field strength is greatest; this is from wherever the radius of curvature of the surface is smallest, i.e. from a sharp point or edge rather than a flat surface (see Corona discharge). It would be easiest to pull electrons from a pointed electrode but a pointed electrode would erode after only a few seconds. Instead, the electrons emit from the sharp edges of the end of the electrode; as these edges erode, the spark becomes weaker and less reliable.

At one time it was common to remove the spark plugs, clean deposits off the ends either manually or with specialized sandblasting equipment and file the end of the electrode to restore the sharp edges, but this practice has become less frequent as spark plugs are now merely replaced, at much longer intervals. The development of precious metal high temperature electrodes (using metals such as yttrium, iridium, platinum, tungsten, or palladium, as well as the relatively prosaic silver or gold) allows the use of a smaller center wire, which has sharper edges but will not melt or corrode away. The smaller electrode also absorbs less heat from the spark and initial flame energy. At one point, Firestone marketed plugs with polonium in the tip, under the questionable theory that the radioactivity would ionize the air in the gap, easing spark formation.