I checked #8 sparkplug last weekend and the center electrode was rounded so I decided to replace the plugs. It had Champion 4701 truck plugs in it and other than the electrode being worn they had good color. Maybe a heat range too hot. I went with the Autolite AP5224 platinum plugs and the truck runs 100% better.
I was reading over the weekend and it seems Platinum plugs aren't the favored plugs with members of the forum but I never saw any reason given.
What's the problem with platinum?

 

Copper plugs are usually the preferred plugs for our truck, because our old trucks were designed to run with copper plugs. I haven't seen any actual evidence, but many people on this forum are firm believers in the copper plugs

 

There seem to be longevity problems with the rare-earth plugs..... They just don't last as long as they should. Some have gotten less than 5000 miles out of 'em, before they had to be replaced. It's really a crap shoot though. Some folks have had great success with them, others... well, not so much so.

 

What forum were you reading? LOL If you have a problem with the #8 plug. I suggest you read this thread. https://dodgeforum.com/forum/2nd-gen...um-thread.html

 

i once believed that 'the more the $$, the better the performance'.. boy, was I wrong..

it's been my experience, that the platinum and iridium plugs are only worthy of use if you've built to support higher voltage spark, and where you can open the gap considerably.. like, .060 from .035 stock considerably..

I experienced metric tons of pinging with the hotter plugs with the OE ignition and OE gaps.. the plug is simply too hot.. it is hot enough to fire the load before spark is applied.. good ol' copper plugs don't do this except in extreme conditions.. the cooler coppers won't do it at all- unless something else is going on with your engine..

if you install a higher voltage ignition, you can increase the gap on the plug because the voltage can easily bridge the gap.. this means an already cooler plug runs even cooler, and the wider gap provides more surface spark to more positively and thoroughly ignite the charge when it should.. = that equates to cleaner burn, more power, and better mileage.. it also means about $300 minimum in parts and pieces..

you gotta figure, the cost of getting into the better ignition against the cost of copper plugs.. you could change the coppers out ten times or more before you approach the cost effectiveness of hotter coils, stouter wires, better dizzy caps, and rare-earth plugs..

I would do it without blinking an eye if i lived in higher elevation.. until then, good ol' copper is the better choice..

 

I was reading this forum, of course! LoL

No, I wasn't having any issues with #8 but I had read about the plenum issue and I figured if I was going to check just one plug then I would check #8. The only reason for checking is that it had a slight rough idle. And it did need plugs. I was going to reroute the wires per the TSB but ran out of time. I'll be doing that next.

 

I came in about a six pack shy of three Benjamins, about a third of it in the ain't no kill like overkill plug wires. I probably should have spec'd a cheaper wire, but I was feeling silly and also not like finding out halfway home from my tuneup that I had problems -- I did the swap 500 miles from home. I might try something cheaper at my next tune-up in 90,000 miles or so.

 

Whether Platinum (or Iridium) plugs work best is really engine specific. You can try them if you feel like spending a few extra $$.

If you are considering which plug to buy, regardless of what you choose, take a moment to set them up right and chances are they will be fine. Advanced plug designs are there to solve a problem that exists; if the engine runs perfectly then there is no need for a fix in the first place.

Easy to do is make sure they are gapped correctly first of all; check "pre-gapped" plugs to make sure; mistakes are hardly unheard of in a brand new pre-gapped plug.

I prefer factory gap and if given a range, on the low side (closer, or smaller gap). The reason I feel that way is first of all, if it isn't firing you're not going to see any benefit from any plug. Misfires are not always obvious.

Secondly the next thing to do is to index the plugs. This insures the open part of the plug, where the spark will be generated, is facing the part of the chamber with the best mixture velocity and A/F ratio. This is usually either toward the intake valve or toward some other part of the chamber on the intake valve side.

If all cylinders are indexed, there is much less need to try to un-shroud the spark by using large-ish gaps, so you can then choose a gap the ignition electrics can support with adequate spark energy at all engine RPMs, all cylinder pressures, and all normally expected A/F ratios.

Rare Earth centre electrodes, aside from the ability to support spark when reduced ignition spark energy might not light a conventional plug, are usually much smaller in diameter at the centre electrode. This is an attempt to un-shroud the spark more than with a copper plug, and to use a material that is more resistant to self-heating and contributing to pre-ignition.

It is not easy to say if any of those benefits would solve some issue in a given engine, or if the engine has no real issues to solve in the first place. I would consider the Magnum head to be a relatively modern design with generally fewer spark issues than, say, a classic Hemi head (most gas airplanes, pre-80's Harleys, Porsche's classic boxer engines, early Chrysler Hemi's, etc). So my own gut feeling is you might be fine with an inexpensive plug. I just installed NGK V-powers and they seem to be doing fine; they were on sale.

No plug is going to "increase horsepower and gas mileage" but certainly a given plug could reduce both of those from what the engine is capable of.

 

Truth, but with a minor caveat: If you're running close to a given engine's margins, the ignition system starts to matter, all the way to the plugs. Most of us have no reason to think twice -- our engines do pretty well over a wide range of conditions. I like to knock around at low RPM where the air gets mighty thin so I want a wide gap and a sizzling arc to consistently light that slow moving wispy mix. I might get by without it, but this way I don't have to worry about being a tad short on power when I really need it to get back home again.

FWIW, if anyone wants to index his plugs in a Magnum V-8, point the gaps at the intake valves and the shadow will land right on the strap.