As I stated above, my stock vehicle when torn apart at 55K only had two original AC double-platinum plugs left with both platinum pucks still on them.

But, the last 30K miles have been with Autolite double-platinum plugs in AFR heads, cammed and such, with no problem -- I've pulled the plugs twice and checked them (never had to gap any).
These plugs have seen much more "aggressive" driving than the AC originals.
I can't help but wonder if the AC plugs weren't designed correctly.

Tom Piper

 

I looked up some info about copper, platinum, and iridium, the three most common metals used in spark plug manufacture. Got the info from this site: www.scescape.net

Copper

Melting Point: 1356K
Electrical Conductivity: 595.8 1/mohm-cm

Platinum

Melting Point: 2045K
Electrical Conductivity: 94.34 1/mohm-cm

Iridium

Melting Point: 2683.2K
Electrical Conductivity: 188.679 1/mohm-cm

Of the three, looks like iridium comes out on top for durability. What I wonder though, is if the reason for having 4 igniters on the +4's might be to "spread" out the heat that the plug see's between four instead of having it all focused on one? I'm running a set of these with my Delteq setup and haven't had any problems yet but if I do I think I might consider iridiums as a replacement.

 

"4 ignitors" is a worthless gimmick.... the only possible benefit would be longer plug life. In return, you are shrouding the flame kernel, and adding mass to the tip of the plug that will absorb heat and act like a glow plug in nitrous or forced induction applications. The spark, when offered the choice of "4 igniters" simply jumps the smallest gap on a single electrode, and nothing happens at the other 3. When that "smallest gap" electrode gets burned away, the spark moves to the electrode new smallest gap. I am amazed at the poor performance of so many Bosch products, including their spark plugs, O2 sensors and even there wiper blades. Only their injectors and fuel pumps seem to have the expected quality.

Do NOT use gimmick spark plugs... +4's, Split Fires, E3's etc. They do nothing for you, except possibly extend plug life. In the case of the Split Fires, the base quality of the plugs it terrible, and the "split" electrode looks like someone in a slightly innebriated state opened it up by hand with a pair of dikes pliers.

NGK and other platinum plugs seems to not have the problems the stock AC/Delco plugs have with losing the electrodes. My 2001 Silverado came from the factory with NGK platinum plugs.... even GM seems to have discovered that the AC/Delco plats had a problem. And NGK appears to have replaced their platinum plugs with Iridium. AC/Delco now has an Iridium "Professional" plug.

 

The reason they put the exotic metal plugs in them is for 100,000 mile tune ups and the 50/60 thousands gap is for emissions.
Do a survey at an NHRA event or the saturday night circle track and see if they are running exotic metal plugs.
I am liking the ZEX plugs.

 

I never even knew ZEX made plugs.

Copper: +1 for conductivity
3 igniters: +1 for longevity.

Good find.

 

If ya call ANY of the major plug manufacturers they will recommend a plug for your or any set up.

 

Lots of good info in the replies.

I was running between .050-0.060 gap. I'll close them to .035 for the next opti and see how that works.

 

Fred, .100"??

 

Yes.... with the stock gap, lose one platinum puck and you have a 0.075" gap, lose both and you are at 0.100"

 

Yes, and then add higher compression, ported heads, a cam, and an Accel 300+ that can really pump up the voltage to fire that excessive .100" gap and zowie -- that will really fry the cap and rotor of the Opti-Spark.
Time for a LTCC or Delteq.

Tom Piper