Originally Posted by Red Devil

Wow, it amazes me how much misinformation is on this site. Iridium has been around for a while. As for conductivity:

Copper:
Thermal conductivity 401 J/m-sec-deg
Electrical conductivity 595.8 1/mohm-cm

Platinum:
Thermal conductivity 71.6 J/m-sec-deg
Electrical conductivity 94.34 1/mohm-cm

Iridium:
Thermal conductivity 147 J/m-sec-deg
Electrical conductivity 188.679 1/mohm-cm

As you can plainly see, COPPER is the best conductor of the three. That is inclusive of the thermal conductivity. That said, the latter two in the above list are much more durable substances in the combustion environment. When the big thing a few years ago was the 100,000 mile tune up, it was Platinum and Iridium plugs placed in the motors. They are produced for durability and durability only. You will note that a lot of companies do not use full sleeved platinum or iridium.

There is a drawback to their durability, as stated previously, in that their conductivity relatively sucks donkey *****. You can not use full platinum plugs such as Bosch platinum and Bosch +4 with a capacitive discharge system (not sure if anyone makes a full iridium plug but allegedly the stock v-8 SHO ones were). The resistance will either ruin the plug or the capacitive discharge system or one of the ignition components.

For these applications the consensus has been the regular Bosch (solid copper core) AC Delco or Champion plugs.

Now as far as changing the plugs, I’ve owned about a dozen of these cars and always pulled them from the top with little problem. :shrug:
As far as the less powerful ignitions of today… where? The output is comparable for the most part, they are all ‘HEI’ ignitions now a days.

As for our cars fouling the platinum and iridium plugs, that is pure BS. That is one of the good points of all that resistance and minimal electrode surface area, they self clean rather well and stay cleaner longer.

Originally Posted by Red Devil

Any quality copper core plug would be what you want. Certainly not a Bosch platinum (any) with the MSD, they get too hot. You want the least inline resistance when using an aftermarket ignition. (Don't get me started on the alleged 'low resistance' crapola wires MSD and others sell.)

Any of the expensive metal plugs are typically not needed on these cars (particularly with a 'hot' ignition set-up) unless you plan on neglecting your tune up interval. As was mentioned, these plugs are pretty easy to get to.

If you want to 'get a little extra' index the plugs and cut back the strap halfway into the center electrode.

Originally Posted by Red Devil

Contextually...

Multi-prong plugs are worthless in our motors. At best they are a waste of money, at worst they will impede the flame front in the combustion chamber.

If you don't like doing plugs often, Bosch Platinum are fine (single plain old platinum) SO LONG AS YOU DO NOT RUN AN AFTERMARKET IGNITION!! Not so good for reading the plugs either, but longevity is great. Same with all the funky metal plugs.

Bosch copper core (Cu conducts better than all those funky metals), AC Delco, Champion all the 'regular' plugs are fine as well if you feel you don't mind changing them more often, or you need to read the plugs.

Wires... depends on the ignition. Aftermarket ignition will typically call for thicker/better wires. Stock ignition, you can use stock-type wires.

On a 305 TBI... anything is fine.

Originally Posted by Vader

LBC,

SplitFires probably don't "suck", and they likely don't "blow" either. In other words, they are really no better nor worse than a "conventional" spark plug, so why spend extra money for something that has no gain.

Millions of man/hours of research and development have been invested in the present evolutionary phase of the spark plug. If pressing a split end in the outer electrode were such a great advantage, you would see that design on aircraft plugs and every other brand of automotive plug. You would also discover that moving the spark all over the combustion chamber is not a good thing. The entire reason that people INDEX their spark plugs in maximum=performance engines is that it is critical to have the spark in a controlled and consistent location. Allowing the spark to wander all over the face of a wide or split outer electrode is contrary to that theory, and also contrary to the theory of having a small center electrode like you'll find on true platinum-cored plugs.

The SplitFire design has been in the public realm for more than seven years, and if it were "all that", everyone else would be using the idea now that the patent has expired. If you can get them on sale for 99¢ then by all means get them if that's what you desire. Otherwise, the cost differential probably doesn't justify the difference.

Platinum electrodes, however, are a completely different story. True platinums (not platinum clad steel like some plugs) are a definite advantage for wear and reliability, and consistent spark location.

For the same reasons listed above, I feel the Bosch 4+ plugs are even less desireable. It would be freakin' near impossible to predict the spark location and flame kernel travel with that plug. To me, they are in the same category as oil additives and magnetizers on fuel lines - they sound good on paper using circular logic, but the science doesn't support the theory.

But that's just my opinion...

------------------
Later,
Vader
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"Fear is how I fall, Confusing what is real..."
Adobe Acrobat Reader

Originally Posted by Red Devil

Sure, so long as the other three electrodes don't block the flame front.
The point of the indexing is to expose the flame front to the rest of the area w/o impeding it's flow by moving the strap to the back of the flame front generated by the spark. That's why the +4's would work in alot of imports. The heads centrally locate the plug at the top center so the flame front you want to propegate is generally below the electrodes.

Originally Posted by Red Devil

from:http://www.sdsefi.com/techcomb.htm

"Ignition Wires

The purpose of the ignition wires is to conduct the maximum coil output energy to the spark plugs with a minimum amount of radiated electromagnetic interference (EMI) and radio frequency interference (RFI). On most street applications using digital computers for engine management control, excessive EMI and even RFI can interfere with ECUs and cause running problems.

There are 3 basic types of conductors used in automotive applications: Carbon string, solid and spiral wound. Most production engines come equipped with carbon string or spiral wound. The solid core types are used exclusively for racing, mainly with carbureted engines because they offer no EMI or RFI suppression. They generally have a low resistance stainless steel conductor. These types are rapidly losing favor, even in racing circles.

The carbon string type is the most common and work just fine in most stock type applications. The conductor is usually a carbon impregnated fiberglass multistrand. Suppression qualities are fine with resistances in the 5K to 10K ohms per foot. They are cheap and reliable for 2 to 5 years usually, then they may start to break down and should be replaced. High voltage racing ignitions will likely hasten their demise.

The spiral wound type is probably the best type for any application. The better brands offer excellent suppression, relatively low resistance and don't really wear out. Construction quality and choice of material vary widely between brands.

NGK makes low priced wire sets which work well in performance and street applications however the terminal ends tend to be a bit fragile.

Magnecor makes excellent quality spiral types with high suppression qualities. These are reasonably priced for the quality you are getting and proven worldwide over many years under extreme conditions.

Some amount of resistance is required along with proper construction to achieve high suppression levels. Resistance is also important to avoid damaging some types of coils and amplifiers due to flyback and coil harmonics. Beware of wires claiming to have very low resistance. These CANNOT have good suppression qualities."

Gotta love search engines.

Originally Posted by jonmark1985

Iridium is to hard to fire and should really only be used in a coil on plug aplication, as the plug wires will short before the plug fires. Or thats what the represenative from NGK told us.

+1 on the bosch multitip is crap stuff, its also dangerous to your engine, as parts fall away from the spark plug when it burns uneven.

Originally Posted by SpitotRs305

hey sorry if i offended you... i have Had some personal experience with Bosch's quality control or lack there of...

i used to run their WR8EC's in my ZX1100-GPz well that is until one day down the highway it went pop engine locked up good had it towed home one of the center electrodes fell in... about 2 days after i installed them... Bosch says they will replace the plugs but any incidental damage isn't their responsibility

Originally Posted by Red Devil

Bad rep, I wouldn't believe a word out of his mouth henceforth. Next time you see him ask him why it doesn't happen with platinum setups (likely he'll reply it's conductivity is better), then pull out the info I posted above when he puts his foot in his mouth.