Sparkplugs
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Joined: Sep 2001
Posts: 4,411
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From: Wilmington NC
Originally Posted by harleyvette
Time to change the plugs. fifty something miles.
Any suggestions on what kind or should I just remain with factory plugs?
This is a stock 98 c5.
Any suggestions on what kind or should I just remain with factory plugs?
This is a stock 98 c5.
www.sparkplugs.com
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Joined: Apr 2004
Posts: 16,135
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From: Newberry FL
Cruise-In VIII Veteran
St. Jude Donor '07
Originally Posted by Richin Chicago
The factory plugs (platinum insert) you have had been supreceded with an iridium plug. I have had very good luck with the NGK iridium TR55IX. It used to be you had to chose between best life and best performance but I believe the irdium gives you both due to it's very low profile and long durability.
www.sparkplugs.com
www.sparkplugs.com
My 2 pennies worth.
Micah
Race Director
Joined: May 2001
Posts: 15,323
Likes: 2,077
From: Guelph, Ontario
Originally Posted by harleyvette
Time to change the plugs. fifty something miles.
Any suggestions on what kind or should I just remain with factory plugs?
This is a stock 98 c5.
Any suggestions on what kind or should I just remain with factory plugs?
This is a stock 98 c5.
Safety Car
Joined: Sep 2001
Posts: 4,411
Likes: 1
From: Wilmington NC
Originally Posted by Patman
I just replaced the plugs in my 98. I bought the car used, with 32k on it, and the original plugs were terrible. The gaps opened up to .070 to .080 in a lot of them, and they were causing 7 degrees of knock retard. Fresh NGK TR6 plugs gapped at .050 brought the KR down to zero. I wanted TR55s but this shop had none in stock when I was there (I was getting it dyno tuned) I have since bought TR55s and will put them in soon. The C5 plugs are so much easier to do than the LS1 f-body plugs by the way!
You probably know this but the reason the gap is there is because Delco added a very very small platinum insert to the negative copper electrode. Whatever joining method they used wasn't good and the piece of platinum came off. I would guess they blow right out the exhaust port because they are no bigger than a pencil dot.
You might want to consider the iridium plug as I, now, have seen write ups that suggest you will get better firing than with conventional plugs because of the iridiums smaller profile.
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Joined: May 2001
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From: Guelph, Ontario
Originally Posted by Richin Chicago
You might want to consider the iridium plug as I, now, have seen write ups that suggest you will get better firing than with conventional plugs because of the iridiums smaller profile.
The iridiums are big $$$ here though, about four times the price of copper TR55s. And since they probably don't give any extra power, I'd just rather stick to the copper ones and change them once or twice per year. Plug changes on the C5 are super simple.
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Safety Car
Joined: Sep 2001
Posts: 4,411
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From: Wilmington NC
Originally Posted by Patman
The iridiums are big $$$ here though, about four times the price of copper TR55s. And since they probably don't give any extra power, I'd just rather stick to the copper ones and change them once or twice per year. Plug changes on the C5 are super simple.
Interesting little snip in Road and Track:
From Road and Track Technical Correspondence September 2004:
"Sparkplug electrode material does not play a direct role in spark intensity. However, platinum and iridium electrodes can be much smaller, notably reducing misfiring because they result in more robust flame kernels. This is because the smaller electrodes are less of a shroud, exposing more mixture to the flame front.
An unusually dramatic illustration of this is with aftermarket supercharged engines running high boost. Such engines often falter terribly at high boost and high rpm due to ignition failure. Simply screwing in iridium-tipped sparkplugs typically eliminates the misfiring and allows the engine to rev to its power peak. In practice, this means a simple plug change is worth 30 bhp simply because the new plugs allow the engine to reach its designed redline."
Last edited by Richin Chicago; Sep 11, 2004 at 11:50 PM.
Race Director
Joined: May 2001
Posts: 15,323
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From: Guelph, Ontario
Originally Posted by Richin Chicago
Can't you get NGK Iridium for about $9.00 CDN at www.clubplug.net?
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Joined: Jun 2002
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From: Columbia MD
Originally Posted by Patman
The iridiums are big $$$ here though, about four times the price of copper TR55s. And since they probably don't give any extra power, I'd just rather stick to the copper ones and change them once or twice per year. Plug changes on the C5 are super simple.
Race Director
Joined: May 2001
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From: Guelph, Ontario
Originally Posted by vetdude
Got mine off eBay for about $45, brand new. Do a search in Parts&Accessories using "NGK."
Safety Car
Joined: Sep 2001
Posts: 4,411
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From: Wilmington NC
Originally Posted by Patman
Like I said, still too much $$$. I picked up a complete set of copper TR55s for under $20 Canadian, which is about $15 US.
Instructor
Joined: Jun 2004
Posts: 120
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Originally Posted by Oldvetter
I replaced mine with Bosch Plus 4, seems throttle reponse is better. I have used Bosch Plus 4 in all my cars.
I have run Bosch Plus 4 in two Corvettes and a Z28, and couldn't be happier with their performance. Much better than stock, for sure. All of the cars seemed to idle smoother and respond better. 
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Joined: Oct 2000
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From: Monticello MN
Originally Posted by Evil_Bob
I have run Bosch Plus 4 in two Corvettes and a Z28, and couldn't be happier with their performance. Much better than stock, for sure. All of the cars seemed to idle smoother and respond better. The Plus 4's made a believer out of me.Ed