AC Delco Rapidfire #5 Spark Plugs

[Rob]

A couple weeks ago, I replaced the spark plugs I had in my ZR-1 (AC Delco Rapidfire #5) with a new set of #5s. It probably wasn't necessary as the old set had about 10-12K miles on them and they were still pretty clean, but I figured, what the hell.

I went to the local parts store and bought a new set. Upon inspection at home, I found that I had two different spark plug tip designs. One has a pointed/crowned electrode. The other is a blunt, rounded electrode. I checked the identification marks on both types of plugs as well as the packaging. All indentification marks indicated they were AC Delco Rapidfire #5 plugs.

The only difference in packaging on some of the plugs was the #"5" was in red and in blue on some of the packages. Some of the packages indicated that the gap was preset to .045 and not to reset the gap. This was not present on the other packages.

I went back to the store and returned the plugs with the rounded electrodes so that I could have a matching set.

I contacted AC Delco this morning regarding this issue and this is the response I received:

Thank you for writing ACDelco.

The RAPIDFIRE Platinum spark plugs have been updated with new features and benefits. These updated spark plugs will be called RAPIDFIRE Platinum spark plugs. The new features focus on changes to the center electrode, the side electrode (also known as the ground electrode) and the insulator.

We do not advise someone to purposely mix the new RAPIDFIRE PLATINUM and the older RAPIDFIRE PERFORMANCE plug because the gap may differ and there are 2 different change intervals. If they were mixed by accident and each one was installed with each one's specific gap and durability, that may be acceptable but not desirable.

It should be noted that none of the packages indicated that they were platinum tipped plugs. So....my recommendation is, make sure that before you leave the store, with a new set of #5s in hand, make sure the electrode design is the same on all 8 plugs.

[WhalePirot]

After many not-so-happy returns to the parts house, I take the old part(s), if possible and check the new; but not with plugs. Guess I'll be more careful.

The new plugs remind me of the 'Fire Injectors', I bought years ago from JC Whitney. The grounding circle was 'castled' and the inner electrode was flat-domed. This design allowed the spark to flow to many spots, lengthing the life. The spark was not shielded by an electrode so the burn seemed better, with increased idle speed in that carbed engine, and better economy. They were real easy to clean, required no gapping and lasted for nearly 100k miles in my old MB. That, in a day when plugs were good for 20-25k max, unlike today, when 100k is not uncommon.

I have not been able to find them for years, now. Some local gear heads recommend Delcos in GM, and others, in the others.

I'd like to know how they work in the car. It may be hard to notice any better burn characteristics, as idle speed is ECM controlled, seat-of-the-pants is less than scientific and most of us don't keep precise comsumption numbers.

Please keep us posted, Rob.

Mike

[Rob]

As a followup, I asked ACDelco why the spark plug packaging does not indicate that they are platinum tipped plugs. Here is the response I received:

The preset ones are the old ones. The new ones say gap to vehicle setting.

Thank you for your interest in ACDelco.
ACDelco Customer Assistance

[secondchance]

That does'nt answer your question. Your inquiry was about packaging not indicating the plug being platinum tip. Their answer is in reference to gap.
From what I understand, platinum tip stays hot and resists fouling and degradation resulting in initial gap being maintained better than the conventional tip. However, I have yet to read anything about nature of the spark itself (i.e. duration, hot or cold relative to copper electrodes). For some reason, I never had good experience with platinum tips. I understand why these are desiable for the manufacturer ( 100,000 miles without tune-up claim). Anyone out there with information on this?

[Rob]

Originally posted by vettaholic
That does'nt answer your question. Your inquiry was about packaging not indicating the plug being platinum tip. Their answer is in reference to gap.

Exactly! I'm not sure I'm done pursuing the issue yet...

[secondchance]

Particular platinum plug I had problems with have "41-913" stamped on the shaft. Could you check for part number on ACD R#5?

[Rob]

Originally posted by vettaholic
Particular platinum plug I had problems with have "41-913" stamped on the shaft. Could you check for part number on ACD R#5?

I have the plug and box in front of me. There isn't a part number on either one. I was told by the parts shop that they go by #5 or #4, etc.

I'm going back to the shop tonight to purchase a couple extra plugs in order to take pictures. I want to send the pictures showing the packaging and plug tips to ACDelco. The fact that the packaging is misleading in that it indicates they are all #5s when in fact, some major changes were made to the plug itself and parts stores are selling "new and old designs" together, is not right.

[secondchance]

Most people could'nt careless. Of course, us vette nuts, especially the ZROners, are too meticulous for this kind of indifferent bs.

[Rob]

Upon further research....according to ACDelco's site, all Rapidfire spark plugs are Platinum tipped plugs. Whether or not this was always the case, can't be determined as of yet, however the following is information I found from their site:

Why ACDelco RAPIDFIRE® Platinum

ACDelco RAPID Platinum Spark Plugs have been redesigned for improved performance your vehicle demands, for longer life and optimum efficiency.

Features include:

Ribless insulator that improves the seal
Tapered center wire electrode with platinum pad
Platinum tip provides improved durability
Greater fuel economy
Consistent starts in all weather conditions
Smoother idle
Available for most vehicle makes and models, including marine applications
ACDelco RAPIDFIRE also has a 30-day, money-back guarantee that's equal to or better than most competitor warranties.

Parts Information

A Closer Look Independent Study Results

Nickel-Plated Shell
Corrosion-resistant, easy to remove

Reduced Firing Diameter
For smoother idle and quicker, more consistent starts

Clipped Gap
Promotes better combustion, smoother idle

Platinum-Tip Center Electrode
Provides improved durability

Nickel-Silver Ground Electrode
Prolongs electrode life

Extended Ground Electrode
For better combustion, fuel economy and performance

Tapered Center and Ground Electrodes
With a column center wire electrode with a platinum pad, for smoother idle and more consistent starts

[Rob]

I spoke to ACDelco this morning and requested specifications for the Rapidfire #5 spark plug. This was their response:

Thank you for writing ACDelco.

At this time we can not give out that information.
Thank you for your comments. We have forwarded your email to our Website Development Group.

Thank you for your interest in ACDelco.

ACDelco Customer Assistance

[Edmond]

Is AC Delco GM owned and operated?

I'm asking because the only AC things I've bought are plug wires. I went with Bosch +4's because so many recommended them.

[secondchance]

Rob,
From what I gather old ACD Rapidfire#5s were copper tipped, then they changed, under same name, these plugs to platinum tips. Am I right? If so any price change?
If you don't mind me asking, what did you pay for a set of 8 most recently.

[Rob]

Ok. I was finally able to take some pictures of the two different types of ACDelco Rapidfire #5 spark plugs that I've been talking about.



Here we see on the left, the ACDelco Rapidfire "Performance" #5 Spark plug. On the back of the package, it states: "Set gap per vehicle specification." You can see that on the end of the box is a red #5. The plug says ACDelco with a 5 underneath.

On the right is the ACDelco Rapidfire #5 spark plug. It states on the back: "Gap preset at .045 DO NOT RE-GAP." On this plug, there is a #5 on one side and "AC" on the other. On the ends of this box (not shown) is a dark blue #5.

In the picture below, you can see the different tip designs.



Now, according to ACDelco above:

The RAPIDFIRE Platinum spark plugs have been updated with new features and benefits. These updated spark plugs will be called RAPIDFIRE Platinum spark plugs. The new features focus on changes to the center electrode, the side electrode (also known as the ground electrode) and the insulator.

We do not advise someone to purposely mix the new RAPIDFIRE PLATINUM and the older RAPIDFIRE PERFORMANCE plug because the gap may differ and there are 2 different change intervals. If they were mixed by accident and each one was installed with each one's specific gap and durability, that may be acceptable but not desirable.

As you can see, nowhere on the packaging does it indicate that either plug is a platinum tipped plug and if you aren't careful and look at the tip design prior to installation, you could be doing exactly what they advise against doing. If you do to the autoparts store and ask for ACDelco #5 spark plugs, counterhelp will hand you whatever it is they have in stock. I bought these plugs at an auto parts store in McLean, VA tonight. The guy handed me two boxes with the dark blue #5 on them. I told him I needed the ones with the red #5 on them. He looked at me oddly and asked....."there's a difference?"

Yep.....there is. So....what's the moral to all of this....becareful what you buy.....I'm now running old outdated spark plugs in my Vette and if I didn't look at the tip design carefully, I could have easily mixed both types of plugs upon installation.

[Demps]

I figured this out a while back. Sorry, I've been gone.

The RED vs BLUE # on the box indicates which type they are. The small tipped one is platinum and should extend the service life of the plug. The stores have a mix and match of each--until the non-plat. serrated ones are sold. I have #5s in one car and #9s in the other. I pulled one of the #5s the other day to check it and don't think I'm going to get 10k miles out of it. Currently on about 1,000 miles and the tip was slightly worn.


The 41-913 is the DEVIL!!!! It is the replacement plug for the 41-907 (or 6 which is the original eq. on 95s, at least). These have two platinum pucks welded to the electrode and ground. The one on the ground will come off. I had a skip/hesitation when accelerating in a cruising gear. Turned out two plugs were gapped at 0.065" because the d@!^ tips came off. Where did they go??????

My recommendation is if you have 41-913 in your car--take them out. Accept changing the plugs more often. They can do some damage if the puck ends up in a valve seat.

[secondchance]

Yeah, I had those crappy 41-913. I kept checking electrodes for 8 months because the car was hesitating which got progressively worse. Turns out one of the plug was arcing from the shaft to the cylinder head! I paid $60 for a set of worthless junk.