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C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Spark plugs

 
Old 06-12-2019, 08:26 PM
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90DayDave
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Default Spark plugs

Wondering what the best spark plug is to use in my 1987 L98?
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Old 06-13-2019, 07:42 AM
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BuckeyeROC
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I like and use the NGK Iridium's. Just put them in our 86E Vette project, too.
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Old 06-13-2019, 08:32 AM
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aklim
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I don't like to use expensive plugs. Their claim to fame is you don't have to replace for 100K and so on. If that happens, great. The price you pay is that there might be more risk of plugs sticking in the head, you don't get to see what the condition of the plugs is as far as whether there is oil going in or there is coolant and probably others I am forgetting. I also like to really know if it can keep the stock gap for that long. I have seen plugs that had a much wider gap after 75K before. So it will run "just fine" except for the larger gap which you don't know of and how it changes things. I have gotten a little more mileage right after a plug change when the gap was wider than it should be.
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Old 06-13-2019, 06:16 PM
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90DayDave
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Thanks.
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Old 06-14-2019, 03:48 PM
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ctmccloskey
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Whatever type of spark plug you finally decide on be absolutely sure to use anti-seize on the threads to keep the plugs from getting stuck in the cylinder head. My 1988 C4 has aluminum heads and the steel plugs can certainly get themselves stuck really well if you don't use the anti-seize on them. The Champion Spark Plug Company sells a small bottle of spark plug anti-seize which is thinner than the standard graphite based products out there. The bottle will last many years for most of us and the price is reasonable it saves a lot of aggravation with a stuck plug. If you don't have any of the Champion anti-seize then use the regular stuff on the threads of your spark plugs as it will work but can make a mess.

This lesson was learned when I had a Quad 4 engine with a stuck (original) spark plug. I soaked it, I heated it up and the spark plug still snapped off at the base of the plug where the threads were located so I had to drill out the base and insert a Heli-Coil in that particular cylinder. When my airplane mechanic heard this she started laughing and told me about the Champion anti-seize. I use it on every spark plug I install in any type of equipment and have never had a stuck plug since then.

As far as spark plugs are concerned I would agree with AKLIM about not wasting a lot of money on expensive plugs. I use cheap(er) plugs and replace them when they need it at 25-50 k miles. I would only spend money on Trick Spark Plugs if I knew my ignition system was up to the challenge. My C3 runs higher than normal compression and needs help to fire under the forces exerted on the plugs. I have tried the Iridium Plugs and they work fine but are not worth the extra money. The Bosch FUSION plugs were the hottest firing plugs I had ever tested on my MSD test rig, they too are very expensive and I have no idea how long they would last in my Engine.

Good Luck with your decisions regarding the spark plugs and remember, Always Use Anti-seize!

Best regards,
Chris
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Old 06-15-2019, 11:41 AM
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Y-bodluvr
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Iíve used AC DELCO Rapid Fire #5 in all of my L98 cars with no issues and jut put a fresh set in my 89í
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Old 06-15-2019, 12:04 PM
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I use the old school copper AC Delco R43TS's (cast iron heads) in my '86...and ran AC Delco 41629's (aluminum heads) in my '87. I have always stuck with original replacements in all of my cars.

Make sure you get plugs designated for your aluminum heads. .

BTW...If you decide to use AC Delco, there is a rebate going on now, regardless of which plug you choose to use.
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Old 06-15-2019, 12:22 PM
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aklim
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I guess we need to ask why we're getting a more expensive plug than stock and what it can accomplish and have something quantifiable as a yardstick besides "it feels like something good.". Unless you want to be lied to by your imagination.

If the engine can actually benefit, like I have a higher compression and am set up for 93 octane, buy it. If you are set up with a lawn mower, why pay for 93 octane or race gas?
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Old 06-15-2019, 02:51 PM
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Originally Posted by aklim View Post
I guess we need to ask why we're getting a more expensive plug than stock and what it can accomplish and have something quantifiable as a yardstick besides "it feels like something good.". Unless you want to be lied to by your imagination.

If the engine can actually benefit, like I have a higher compression and am set up for 93 octane, buy it. If you are set up with a lawn mower, why pay for 93 octane or race gas?

For me, it's less maintenance and the iridium plugs are said to last longer. Our 86 will be a daily driver.
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Old Yesterday, 07:05 AM
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GregMartin
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We use iridium plugs for racing which is really about a more consistent spark. Because of the pointed electrode they tend not to foul as much. Iridium spark plugs are specified for my 6.0L LS engine and I have been considering trying them in my 84 Corvette. Again I would only be using them to ensure consistent spark and TBH I donít think itís probably worth it unless you get some cheap. I would still remove them regularly to check/read them. The most important thing with spark plugs is the temperature rating, it should match air density.
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Old Yesterday, 08:08 AM
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95LT1ZF
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I use NGK plugs in everything; jet skis, motorcycles, cars etc. As far as vehicles go, I always use anti-seize on the plugs, dielectric grease in the plug or boot and change the plugs every couple years or 30K miles. Yes, they would last much longer than that, but it is cheap insurance and gives me some time with my son in the garage.
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Old Yesterday, 09:41 AM
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Originally Posted by 95LT1ZF View Post
I use NGK plugs in everything; jet skis, motorcycles, cars etc. As far as vehicles go, I always use anti-seize on the plugs, dielectric grease in the plug or boot and change the plugs every couple years or 30K miles. Yes, they would last much longer than that, but it is cheap insurance and gives me some time with my son in the garage.
I use NGK in everything as well
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Old Yesterday, 11:58 AM
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Definitely get plugs designed for Aluminum heads and remember the iridium plugs have a higher resistance than the copper but last longer. Copper has the lowest resistance.
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