10-31-2020 | #1 |
Join Date: Aug 2015
Location: Magnolia, Texas
Posts: 884
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Iridium Plugs
This has been discussed in other posts, but wanted to add some pics and history. My '91 is ported, full SW exhaust (headers to tips) and tuned.
I installed NGK TR7ix plugs gapped at .050" about 2,500 miles ago. Had dead coil, so replaced it. Wires were good. Had a slight, but noticeable stumble at low rpm acceleration. Decided to pull plugs. What I found shocked me. Only 2 of the 8 plugs remained at .050. Others were about .058. However #7 and #8 were .068! As others have indicated, batch fire and iridium don't seem to like one another. Moved to NGK 4177 (TR6) copper core. Gapped at .045". Engine is back to 100%. Picture of #7 attached..20201030_183430.jpg Sent from my SM-G950U using ZR-1 Net Registry mobile app |
11-01-2020 | #2 | |
Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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Re: Iridium Plugs
Quote:
Pete Polatsidis put me onto AC/Delco 41-602 copper plugs some 8 yrs ago and I've never had a reason to switch (to another plug)! And, the fact that they're only about $2.00 ea. means I can install new plugs every season* (less than 3k miles or <4.8km) and gapped at 0.040" (1.016mm).
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry |
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11-01-2020 | #3 |
Join Date: Nov 2011
Location: Dunbarton NH
Posts: 7,307
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Re: Iridium Plugs
Just checked my plugs (same plug as above), they had about 5,000 miles on them. I would say they were all within the margin of error.
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11-01-2020 | #4 | |
Join Date: Aug 2015
Location: Magnolia, Texas
Posts: 884
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Re: Iridium Plugs
Quote:
Sent from my SM-G950U using ZR-1 Net Registry mobile app |
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11-01-2020 | #5 |
Join Date: Nov 2011
Location: Dunbarton NH
Posts: 7,307
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Re: Iridium Plugs
NGK TR7ix. Sorry, I guess there were two "as above" plugs.
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11-01-2020 | #6 |
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,686
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Re: Iridium Plugs
So what heat range are you all running? I?ve read that Iridiums run a bit hotter than equivalent copper plugs. I?m trying out BKR7Es right now which SOTP seems to like. Also appears to have helped w random knock.
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[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
11-01-2020 | #7 | |
Join Date: Aug 2015
Location: Magnolia, Texas
Posts: 884
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Re: Iridium Plugs
Quote:
Sent from my SM-G950U using ZR-1 Net Registry mobile app |
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11-01-2020 | #8 | |
Join Date: Aug 2015
Location: Magnolia, Texas
Posts: 884
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Re: Iridium Plugs
Quote:
Sent from my SM-G950U using ZR-1 Net Registry mobile app |
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11-01-2020 | #9 |
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,686
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Re: Iridium Plugs
Steve,
I'm using the the FIC injectors which are supposed to be balanced to within +- 1%. However, did not have them flow checked.
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[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
11-02-2020 | #10 |
Join Date: May 2007
Location: Addison IL
Posts: 241
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Re: Iridium Plugs
Denso has recently released a spark plug that is specifically designed for wasted spark ignitions. It has a platinum tipped negative electrode. This addresses the erosion issue associated with the negative polarity spark that half of the cylinders have on wasted spark systems. In addition the negative electrode has a pointy tip that provides an excellent electric field.
The model number is IT20TT. Some parts catalogs only use the part number 4714. It is the same heat range as the OE spark plug and has a tapered seat which is a universal fit for all LT5s. This is an expensive high mileage spark plug, good for at least 40k miles. I agree with Paul that the dirt cheep ACDelco 41-602 works great for 10k miles. |
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