Spark plugs

[Geerhead55]

Sorry to scare you guys off asking about MSD spark plugs,,, I know they're fairly new. Perhaps no one has tried them yet? Maybe they'll pay contingency. Just wondering.
Danny Durham

[astikhossw]

I have purchase 3 set of AR-13 plugs this season and each set has been in the engine and iI check my plugs after every race that I have attended and after every race there was a problem with at least one plug mostly the porcelain was cracking.The saving grace of it all was NAPA took back each bad plug and gave me a new one.

[terry1]

I have purchase 3 set of AR-13 plugs this season and each set has been in the engine and iI check my plugs after every race that I have attended and after every race there was a problem with at least one plug mostly the porcelain was cracking.The saving grace of it all was NAPA took back each bad plug and gave me a new one.

That is interesting.I have never had an issue with my AR-13 plugs.

[quickford1]

Most problems are from over tightening the tapered seat plugs'

[jcw31]

to MEXJOE and Alan sorry for going a little sideways but i am not sure there is a good or bad plug.I dont think these companys take the time to sort plugs for different tiers ,too costly. Ive seen on the dyno v59yc,ar3910
Autolite,r5671a-8 ngk all were within 1 hp .When Autolite came out with their ar racing plugs we were using 23s changed to ar 13 driver came in after the heat and said plugs were garbage went back to 23s and was happy. In a small block mopar drag car ran n9yc champ tried 63 autolite car slowed .05 .I saw a 440 mopar on the dyno 414s accels egt was good a/ f was good 1st time out 2runs the plugs were peppered like crazy. I believe plugs from different companys even though crossed to the same the heat range is a little different.
Alan if you need rc12yc pm, me. I think with any plug unless extremely cold or hot, just changes in timing/jetting can make the engine happy.

Have a happy Thanksgiving everyone
Joe

[Alan Roehrich]

I do not know for sure how much testing and sorting they do these days, seeing what gets sent out in a box often leaves me thinking there's not much QC at all any more. They have to do a fair amount though, because the cost of shipping a lot of bad plugs to an OE would be tremendous.

Despite using the hotter RC12YC, my jetting, timing, and even air bleeds are real similar to Jimmy's tune up, and they make close to the same power, being very similar engines.

A hot plug might cause a problem in a circle track application, where it had plenty of time to get really hot. However, in a drag race engine that leaves the starting line at 100 F, and is barely 160 F at the finish line 10 seconds later, you'd need a really hot plug to have a heat range problem.

[Lee Valentine]

What Alan says, I,ve used hotter plugs in my engines for years. Was told to do this by a well respected engine builder.

[jcw31]

Alan and Lee I agree with you . As Billy said AC rapidfire also champ autolite ngk or whoever all work great. I dont think theres any magic in plugs be it high $$$ or 2$ . The autolites i referenced were supposed to be the same heat range [ar13 vs 23] but they didnt perform/ feel the same at the time for the driver.

Thanks Joe

[Billy Nees]

I finally took the time to "back-to-back" sparkplugs on Saturday and I was a bit suprised at my findings. When I put the car together, I put in the least expensive plugs that W-Mart had. Just basic plugs. I did an A-B-A-B test between them and a set of iridium plugs that I have used in some of my other stuff. So can a $16 set of plugs perform as well as a set of $64 plugs? Not quite, the iridium plugs averaged .034 ET. and .3 MPH faster than a basic plug. Are they worth the extra $48? In a heads-up or qualifying situation I guess they are. You decide.


For what it's worth, this is from my "Under the index for under a grand" thread. The base plugs were Autolites and the good plugs were AC Rapidfires. Are plugs worth the same in a real good HP engine as they are in a not-so-good lo-po engine? I can't answer that.

[Alan Roehrich]

Of note, the AC Rapidfire is a "broad heat range" plug, they're designed to heat up fast and clean off, without getting too hot. Back when they were first introduced, the AC rep who taught the classes I mentioned in a previous post gave us plenty of back ground on them. This may in fact be a really good thing for a race car, considering the amount of time they spend idling and at low speed, as well as being started relatively cold. Add to that the fact that a lot of people set their idle mixture fairly rich, and you can see where a plug with the design attributes of the Rapidfire might help. Having used them in various applications over the years, I'm not convinced the current version is as good as the original version of several years ago. I have however seen them last as long as or longer than the high dollar "precious metal" plugs, and perform as well or better, in many applications.

Smokey Yunick once told me "if you knew how many times your engine actually misfired, you'd be so pissed off, you'd never start it again". What a lot of people don't understand is that most of the noise you hear is from air flow, not actual combustion. Yes, you can hear a dead cylinder easily. But as Smokey once demonstrated, and backed up with data, what you can't hear is how often each cylinder has a partial misfire. I don't think you can solve that problem with trick spark plugs, or trick spark plug wires. I do think you can make the problem worse with the wrong spark plugs. I don't think any one company makes the best plug, or the best plug for all applications.

It should be understood that most of the "precious metal" content in spark plugs is not for more, hotter, or better spark, but rather for longevity, allowing the OE to reach closer to the unrealistic "100K mile spark plug" that is pretty much required by the current emissions standard. It should also be understood that while the "100K mile without a tune up" is a good marketing ploy, what it actually means is that the "tune up" will merely meet the emissions standard at 100K miles. It does not mean that the parts are actually giving you the best performance and economy for 100K miles. They are not. They start to really degrade past 50K. Even if the plugs do not show severe gap erosion, they will show significant build up of deposits.

Odds are, long before you see any of the actual advantages of the "precious metal" plugs, you'll have swapped them out for fouling, deposits, or just habit.

The above is sort of a long way of saying I'm not sure you'll see much of a gain with expensive "precious metal" spark plugs in most race engines. There may be the odd application where you do. However, if you have a good hot ignition system and top quality plug wires, a good set of copper core spark plugs (with the resistor) is probably good enough. Without that resistor, you can end up with "noise" that can cause high end ignition systems (MSD, ICE, etc) to have odd behavior. It could leave you chasing a misfire or flutter for quite a while.

Last, there can be some gains to the "fine wire" center electrode. They warm up fast, and they tend to concentrate the spark kernel.

The rest of the trick stuff, multiple ground electrodes, trick ground electrodes, trick center electrode tips, don't seem to show any gains, and often show losses.