Delco Irridiums..........No Bosch
Best Spark Plugs??
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
Why not use what the guys who built your car recommend .... AC Delco 41-985 which is a "newer" irridium plug (versus the platinum plug installed at the factory).
The plug comes correctly pre-gapped at 0.040 inches and can be bought from any parts store (Napa ... whatever ... ) just give them the Delco part number.
Also, you might want to consider a set of spark plug wires ..... if they've been on more than 50k miles they're probably getting brittle. The GM Performance Parts (GMPP) kit (part number 12495519) are a very good wire at a surprisingly low price. Order one kit, it contains all 8 wires.
The plug comes correctly pre-gapped at 0.040 inches and can be bought from any parts store (Napa ... whatever ... ) just give them the Delco part number.
Also, you might want to consider a set of spark plug wires ..... if they've been on more than 50k miles they're probably getting brittle. The GM Performance Parts (GMPP) kit (part number 12495519) are a very good wire at a surprisingly low price. Order one kit, it contains all 8 wires.
Burning Brakes
Joined: Jul 2004
Posts: 1,202
Likes: 5
I'm using the NGK TR55IX (irridium) that I purchased at Advance Auto -----go to www.advanceautoparts.com to see which store in your locale woud carry the part...Advance Auto is part of a group of stores, depending on the area of the country you're located. The NGK TR55IX is a little bit different than the Delco irridium plugs. According to NGK, their plugs don't protrude as much and cool down quicker and would result in less chance of cracking the ceramic part of the plug.
I had the wires changed to Magnecore 8.5mm wires. I found a really good price and they were drop shipped from Magnecore. Had it not been for the price, I would have gone with MSD or the GM performance wires.
Note: All the Irridium plugs, from any manufacturer, are pre-gapped & all recommend that the gap not be changed (you'll destroy the plug). I purchased a few extra plugss in case the gap was off, which it wasn't. I returned the unused extra plugs.
I had the wires changed to Magnecore 8.5mm wires. I found a really good price and they were drop shipped from Magnecore. Had it not been for the price, I would have gone with MSD or the GM performance wires.
Note: All the Irridium plugs, from any manufacturer, are pre-gapped & all recommend that the gap not be changed (you'll destroy the plug). I purchased a few extra plugss in case the gap was off, which it wasn't. I returned the unused extra plugs.
Le Mans Master
Joined: Sep 2007
Posts: 7,604
Likes: 8
From: Belleville Il
Most plugs are not properly gapped,,and can be properly regapped.But, and it is a BIG but it has to be done properly.You have to have the correct tool to do it.The new plugs have rather delicate center electrode and most have a small disc on the ground strap electrode.You need a tool that levers the ground from the side so you don't damage either electrode. Most people don't know how to properly do this thus the recommendation not to adjust. I used Delco iridiums. None of them had the proper gap. I set them all at .040 and the car runs like a champ,backed up by Good dyno #s followed by a 13.08/110 with a stock motor and run flats.
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
I never had any problems with the stock but I just fitted NGK TR55s and very happy with them. probably worth fitting new ignition wires at the same time. Its almost impossible to get the originals off without breaking them. I went with GM Performance Reds.
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Melting Slicks
Joined: Oct 2006
Posts: 3,447
Likes: 6
From: Los Angeles
Iridium performs almost as good, but will last much much longer.
If you put miles on your car, and don't want to change the plugs for a while, go with the iridium.
Burning Brakes
Joined: Jul 2004
Posts: 1,202
Likes: 5
The following is from the AC Delco site re: Iridium spark plug:
2003 CHEVROLET CORVETTE Z06 V8 5.7L 350cid GAS FI N Engine VIN = S
Qty Req Qty ACDelco Part# Description
IGNITION / SPARK PLUG
08 41-985 SPARK PLUG, IRIDIUM
GAP .040 DO NOT DEVIATE FROM PRESET GAP .040"
-------------------------------------------------------------------
As I already stated, the factory gap should not be reset, they are properly gapped by the factory. If you find a plug with an incorrect gap, just return the defective plug. When I change plugs, I always buy a few extra plugs since you don't know if the store clerk dropped a few boxes (may cause the gap to change). Whatever I don't need, I return. It used to be common practice to regap plugs. However, with the current electrodes, it is almost impossible to correctly gap a plug. On irridium plugs, the electrode is like a fine wire. Messing with the wire will cause it to become out of alignment. I don't know about the Delco plugs, but the NGK Iridium plugs have a protective semi-hard plastic sleeve that covers the electrode to minimize damage or change in gap.
2003 CHEVROLET CORVETTE Z06 V8 5.7L 350cid GAS FI N Engine VIN = S
Qty Req Qty ACDelco Part# Description
IGNITION / SPARK PLUG
08 41-985 SPARK PLUG, IRIDIUM
GAP .040 DO NOT DEVIATE FROM PRESET GAP .040"
-------------------------------------------------------------------
As I already stated, the factory gap should not be reset, they are properly gapped by the factory. If you find a plug with an incorrect gap, just return the defective plug. When I change plugs, I always buy a few extra plugs since you don't know if the store clerk dropped a few boxes (may cause the gap to change). Whatever I don't need, I return. It used to be common practice to regap plugs. However, with the current electrodes, it is almost impossible to correctly gap a plug. On irridium plugs, the electrode is like a fine wire. Messing with the wire will cause it to become out of alignment. I don't know about the Delco plugs, but the NGK Iridium plugs have a protective semi-hard plastic sleeve that covers the electrode to minimize damage or change in gap.
Thread Starter
Advanced
Joined: May 2008
Posts: 60
Likes: 0
From: Miami FL
Burning Brakes
Joined: Jul 2004
Posts: 1,202
Likes: 5
are these the ones??
http://www.partsamerica.com/ProductD...pe=960&PTSet=A
http://www.partsamerica.com/ProductD...pe=960&PTSet=A
Burning Brakes
Joined: Feb 2005
Posts: 752
Likes: 1
From: Tulsa OK
One of the advantages of the Platinum and Iridium plugs (besides the long service life) is the small tip. The smaller tip diameter (0.6mm in the NGK iridiums and about 1mm in the platinum plugs) allows the spark kernel to form faster and make a stronger spark as it jumps to the ground electrode. This creates a better ignition of the air/fuel mixture in the cylinder and improves the performance of the other ignition components.
They could make a copper plug with a smaller tip but copper is too soft and would burn up too quickly at that small diameter. Platinum and iridium are just as conductive as copper but much stronger/harder. Only the tips are platinum or iridium, welded to the internal core of the plug which is still copper.
Its the small diameter of the tip, not the 100,000 miles that counts. All plugs should be pulled and checked at least once a year - especially in aluminum heads so they don't seize. Who drives 100,000 miles a year in a privately owned street vehicle not used in business? If the longevity of the plug was the only benefit how could you justify the cost. You could replace the copper plugs four times before you reached the cost of the iridium plugs.
They could make a copper plug with a smaller tip but copper is too soft and would burn up too quickly at that small diameter. Platinum and iridium are just as conductive as copper but much stronger/harder. Only the tips are platinum or iridium, welded to the internal core of the plug which is still copper.
Its the small diameter of the tip, not the 100,000 miles that counts. All plugs should be pulled and checked at least once a year - especially in aluminum heads so they don't seize. Who drives 100,000 miles a year in a privately owned street vehicle not used in business? If the longevity of the plug was the only benefit how could you justify the cost. You could replace the copper plugs four times before you reached the cost of the iridium plugs.
Last edited by EStreeter; Jun 2, 2008 at 09:47 AM.
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
http://www.boschautoparts.com/Produc...s/IrFusion.htm
Sounds like Marketing
to me ......
Advanced
Joined: Apr 2008
Posts: 74
Likes: 0
From: Sunnyvale CA
Yeah those are the ones. struck me as a marketing gimmick too, but if iridium is good and platinum is good, those may still be good even if they don't live up to marketing hype. Has anyone tried them out yet?