NGK Spark plugs

**Whamhammer** · 04-30-2017, 11:12 AM

When I got the headers, and cat back done, TR55 plugs were installed also. It seems since then, the p/n has changed. I have two questions:

1) What is the correct new P/N?
2) What is the mileage replacement interval that most have seen on these? 15k? 30k?

**98TransAmWs-6** · 05-01-2017, 03:50 AM

3951 is the part number. I'd change them every 20k or so. Get iridium and you'll go much longer.

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***SMWS6TA*** · 05-01-2017, 05:39 AM

If you have mild bolt on's I'd recommend going with the Iridium plugs. More bang for your buck and not quite a loss with the spark.

**Whamhammer** · 05-03-2017, 06:55 PM

Originally Posted by SMWS6TA

If you have mild bolt on's I'd recommend going with the Iridium plugs. More bang for your buck and not quite a loss with the spark.

I am pretty surprised to you two suggesting iridiums, just before I put my headers on, I thought everyone was solidly in the copper plug camp, even with the build I have. Has something changed?

**98TransAmWs-6** · 05-04-2017, 12:19 AM

I use copper but I'm heavily modified and there is no iridium option for what I need otherwise I'd be doing iridium for the longer last plugs.

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***SMWS6TA*** · 05-04-2017, 06:24 AM

Originally Posted by Whamhammer

I am pretty surprised to you two suggesting iridium's, just before I put my headers on, I thought everyone was solidly in the copper plug camp, even with the build I have. Has something changed?

You noticed I said for stock or mild bolt ons. Copper is always better for higher/hotter spark over Iridium, however Iridium does last 3x longer than copper but has a decrease in spark intensity.

I did try both, when I had just headers, LS6 intake and not taking it to the track. Once I started going to the track more and mod'ing more I had to swap over to the TR55's because the iridium plugs were not lasting as long under the harder load I put on them. When you change plugs every 25k miles or after X amount of track days, like in my case almost 3x's a year it gets expensive buying iridium's.

Like Will I'm heavily modified, I currently have to use a TR-6 plug for now and may end up going next range down on future mod.

**pajeff02** · 05-06-2017, 02:12 AM

I'll be dead and gone most likely before our TR-55's see 25,000 miles.

**Whamhammer** · 05-06-2017, 03:18 PM

Originally Posted by pajeff02

I'll be dead and gone most likely before our TR-55's see 25,000 miles.

One of these days, when I get a daily driver, I may share in your sentiment. I will still probably drive it 1-2 days a week to and fro work but that's depending on a fairly substantial promotion. Stranger things have happened though

**Whamhammer** · 08-05-2017, 11:00 AM

I'm not doubting the plugs, as I have just picked up another set but how did everyone come to use the TR55's (3951)? The OE specs call for a 40 gap, and a different part number for a NGK plug.