New AC Delco Rapidfire 5

[secondchance]

I had been running NGK Iridium for about a year. Somehow, it just felt the car ran smoother when I ran old non-platinum Rapidfire 5s.
So, I ordered 8 new platinum tipped Rapidfire 5s from the Rockauto.
Well, I got 8 - 2 has larger font red "8" on the box and 6 has smaller font black "8" on the box. Open the box and red 8 lettered has skinnier but longer electrode and black 8 marked box contains shorter but wider elctrode - must have been a production change.
Would you run 2 diffrent types simultaneously?


Longer and skinnier


Shorter but stubbier

[WVZR-1]

Originally Posted by secondchance

I had been running NGK Iridium for about a year. Somehow, it just felt the car ran smoother when I ran old non-platinum Rapidfire 5s.
So, I ordered 8 new platinum tipped Rapidfire 5s from the Rockauto.
Well, I got 8 - 2 has larger font red "8" on the box and 6 has smaller font black "8" on the box. Open the box and red 8 lettered has skinnier but longer electrode and black 8 marked box contains shorter but wider elctrode - must have been a production change.
Would you run 2 diffrent types simultaneously?

That would seem foolish I believe. I'd just have the entire order picked up. There's advantages to "local purchases" ! Lessons learned?

[secondchance]

Originally Posted by WVZR-1

That would seem foolish I believe. I'd just have the entire order picked up. There's advantages to "local purchases" ! Lessons learned?

For sure!

[Paul Workman]

Hard to beat a new set of the ol' AC/Delco 41-602s for our street driven cars.

I hope Bob G or Pete or Marc can chime in here, but for a given set of driving conditons - whatever that may be - the important thing is to establish the proper heat range for the plug. Then, the decision to go with an expensive, rare-earth material plug becomes more of a practical one, driven by how the car is used.

Thoughts?

P.

[WARP TEN]

I was down at Marc's place the Tuesday looking at my engine--whose pieces were scattered around various places in his shop--and he showed me the plugs. They were the original AC 907s (car has about 20k miles on it). They were actually in pretty good condition and the engine certainly ran fine. But one was missing the platinum wafer on the electrode so we are replacing the lot. I think with the NGKs but I can't recall precisely. I remember losing the platinum discs was a problem on my 93's 907s which also went by the wayside. --Bob

[Hib Halverson]

The original Rapid Fire 5 was one of my favorites but it hasn't been made in over a decade. I ran them for a couple of years after it was introduced in the late 90s.

After that I fooled with a bunch of different NGKs.

Then, I tried some Denso Iridium Power plugs and have stuck with them since the early '00-s. They are incredibly durable, have a wide heat range and are available in either flat seat or tapered seat styles.

In my 95, I use the IT-22. It's worked very well in all kinds of driving from easy street to mild racing. I've also used the IT-24 in really abusive chassis dyno testing, but it's a tad on the cold side for any street use.

Interestingly, the IT-22 also works quite well in newer LS6es and LS7s.

RockAuto sells Denso Iridium Power plugs but I just bought 8 of the ten they had in stock. I spoke with the folks at Denso Sales USA last week and they said there is a temporary shortage.