C5 recommended spark plugs

[Krusty]

Can anyone give me a straight answer please about what plugs go in a 2001 C5 Targa?
I would like to buy NGK Iridium plugs and I believe they are TR5IX. The NGK stock number is 7397 (Rockauto provided number).
But when I search for these plugs online, I get conflicted searches saying they won't fit
Surely someone here knows the answer or knows what iridium plug fits

Picture of my engine... just because, well, engine

 

[teamzr1]

For over 20 yeas my 1999 C5 has used the NGK TR6, they are one step colder and gap is a bit shorter for a better idle
I know many others with C5 also using them

As to your engine bay



BTW, what are the electronic boxes on both sides, 3rd party lighting ?

 

[Krusty]

For over 20 yeas my 1999 C5 has used the NGK TR6, they are one step colder and gap is a bit shorter for a better idle
I know many others with C5 also using them

As to your engine bay
View attachment 24776


BTW, what are the electronic boxes on both sides, 3

I can certainly assure you that I don't have ANY dirt on my 4 wheeled pride & joy

As you can see
Do you know the NGK stock number to the plugs you use?
Also, I won the car in a Japanese auction and it came with a lovely set of aftermarket light internals fitted.
The boxes you see are the ballasts for the xenon lights

More proof that I don't have dirt on my car

The car had only 1 owner from new (2001, genuine Japan model). I won it at auction (Nov 2021), had it shipped, collected it (April 2022) and have been loving it ever since. There's nothing visual I want to change on it. Whoever it was who owned it in Japan, is just like me
I managed to find a few photo's of it in Japan but not been able to find the original owner sadly.
Enjoy

 

[Mr. Cricket]

Glad you kept it when it was getting you down a bit.

Reposting just because..

 

[teamzr1]

https://www.ngk.com/ngk-4177-tr6-v-power-spark-plug

If wanting like stock would be but one step colder are the V-power type like TR6 or these :

https://www.ngk.com/ngk-2238-tr5-v-power-spark-plug

I do not like the Iridium type, but if you want that design

https://www.ngk.com/ngk-1465-iztr5b11-laser-iridium-spark-plug

I cannot recall but either NGK was bought up recently or they bought some other competing company and why part #s are confusing

Think I need to come over there and test run your C5 to give it some battle scares

 

[Krusty]

https://www.ngk.com/ngk-4177-tr6-v-power-spark-plug

If wanting like stock would be but one step colder are the V-power type like TR6 or these :

https://www.ngk.com/ngk-2238-tr5-v-power-spark-plug

I do not like the Iridium type, but if you want that design

https://www.ngk.com/ngk-1465-iztr5b11-laser-iridium-spark-plug

I cannot recall but either NGK was bought up recently or they bought some other competing company and why part #s are confusing

Think I need to come over there and test run your C5 to give it some battle scares

Thanks for that, I'm still unsure what to choose then... I'm so use to owning JDM cars and motorcycles, I know they all seem to take Iridium plugs. So I was just sticking with what I know basically
I only use the car to drive around in and enjoy. It doesn't get a hard life or daily use... I do now and then open the taps here and there but nowhere near enough to stress anything.
The most it has done is only a 1500 miles round trip to the Nurburgring this year which included a few laps (photo's below).
So I'm open to suggestions on what would be best suited. Price is not an issue, I only want what is best for the car to perform and be in perfect health




and I'm trying to keep battle scars to a minimum, Thank you

 

[Krusty]

Glad you kept it when it was getting you down a bit.

Reposting just because..

View attachment 24789

I just needed to take a step back and assess the whole situation with it. I bought a car that I knew nothing about and even though has tons of history, I can't understand a word of it (being all in Japanese).
But with the help of everyone here, I got stuck in, and although let's be honest... they aren't the perfect cars, can be quite flawed (especially in the UK). I can honestly say, I am absolutely in love with it!
I can't wait to do more next year. I still haven't been to a club meet yet!

 

[teamzr1]

For mostly street use than go with these as being like stock ones

https://www.ngk.com/ngk-1465-iztr5b11-laser-iridium-spark-plug

 

[Krusty]

For mostly street use than go with these as being like stock ones

https://www.ngk.com/ngk-1465-iztr5b11-laser-iridium-spark-plug

Top man, I've ordered them

 

[teamzr1]

Do not re-gap these, they are set at 0.43 which as fine
and below shows what to torque them to when installing
Write down mileage as they say they work for 100,000 miles

• Shell
• Thread Diameter14mm
• Thread Pitch1.25mm
• Seat TypeTapered
• Reach18mm (.709")
• Hex Size5/8" (16mm)
• Terminal TypeSolid
• Overall HeightISO
• Gap.043" (1.1mm)

• Center Electrode
• MaterialIridium
• TypeFine Wire
• Size0.6mm
• ProjectionExtended Projection

• Ground Electrode
• MaterialPlatinum
• TypeStandard
• Quantity1
• 
  
• Specifications
• ResistorYes
• Resistor Value5k Ohm
• Heat Range5
• Torque SpecsCast Iron: 10.8-18 lb. ft.
• Aluminum: 7.2-14.5 lb. ft.
• Part Information
• BrandNGK/NTK
• Warranty60 Days
• Longevity100k Miles

 

[Krusty]

Do not re-gap these, they are set at 0.43 which as fine
and below shows what to torque them to when installing
Write down mileage as they say they work for 100,000 miles

• Shell
• Thread Diameter14mm
• Thread Pitch1.25mm
• Seat TypeTapered
• Reach18mm (.709")
• Hex Size5/8" (16mm)
• Terminal TypeSolid
• Overall HeightISO
• Gap.043" (1.1mm)

• Center Electrode
• MaterialIridium
• TypeFine Wire
• Size0.6mm
• ProjectionExtended Projection

• Ground Electrode
• MaterialPlatinum
• TypeStandard
• Quantity1
• 
  
• Specifications
• ResistorYes
• Resistor Value5k Ohm
• Heat Range5
• Torque SpecsCast Iron: 10.8-18 lb. ft.
• Aluminum: 7.2-14.5 lb. ft.
• Part Information
• BrandNGK/NTK
• Warranty60 Days
• Longevity100k Miles

It will be a looooooooong time before I get to do 100k miles in my C5
I bought it with 61.2k miles and its currently only on 64.8k miles

 

[FIVE RED]

One of the first things I do when buying a used car is change the plugs. I bought our C5 almost 17 years ago & after reading many posts on Corvette Forum in the US I chose to fit the recommended plugs & wires - NGK Iridium TR55IX with GM Performance wires. Can't say if they made any real difference, but I was happy that I'd fitted decent stuff. Yes they're still going strong

 

[Krusty]

One of the first things I do when buying a used car is change the plugs. I bought our C5 almost 17 years ago & after reading many posts on Corvette Forum in the US I chose to fit the recommended plugs & wires - NGK Iridium TR55IX with GM Performance wires. Can't say if they made any real difference, but I was happy that I'd fitted decent stuff. Yes they're still going strong

I pulled the plugs when I first bought the car and at the time they looked fresh. The Japanese service history showed they had been changed in the recent months prior to me purchasing it.
I did notice my plug leads had age related heat damage and the inevitable happened last year (probably close to 12 months ago now) when they pulled apart from the plug caps. It didn't help that I was messing around chasing oil leaks (cam cover seals... then valley cover gasket). So I fitted a full set of double thick and insulated silicone leads (in red of course, because that makes it go faster... its science ).
Now approaching nearly 3 years since the car last had plugs, I've decided to do them but I didn't make a note of what was in it when I removed them almost 2 years ago (silly me). Recommendations are always welcome however... but I'm happy with the info teamzr1 has given me and have made the purchase, just waiting for them to arrive

 

[teamzr1]

Might be a good idea when you pull the plugs that you mark on them what cylinder it came from
so that you could then read it one and see if any one looks different in color or gap to see if all
cylinders are functioning the same and then save those results if later comparing how the new plugs
look after some time of use

Could chart them by punching 2 sets (for B1 & B2) of 4 holes and then sticking the ends of each plug to than take a
photo of that would allow others to read what the plugs are saying

If not known :

Left bank (B1) has the odd numbered cylinders 1,3,5,7 starting from the front side and
right bank (B2) is even numbered of cyl 2,4,6,8

Remember the new plugs pre-gap is like 0.40 and not using the stock 0.70 gap

 

[Krusty]

Finally got round to doing my spark plugs. Big thanks to teamzr1 for recommending the NGK IZTR5B11 Laser Iridiums. They're a perfect fit

Someone could of warned me about how much of a pain in the a**e this plug is to change!

But it's done now so happy days

Here are the plugs I took out, in order of which cylinder they came out of (the arrow indicates the front of the motor).


Clearly a very healthy running motor, so I'm very very happy

Thanks for all the help and input everyone

 

[teamzr1]

Did you measure the gap on the old plugs ?
Sure looks like they stretched as they look too wide or someone gapped them wrong

If your arrow was pointing to the front, then does it look like cyl #3 has a bit of oil on the threads as maybe a valve cover gasket leak ?

 

[Krusty]

Did you measure the gap on the old plugs ?
Sure looks like they stretched as they look too wide or someone gapped them wrong

If your arrow was pointing to the front, then does it look like cyl #3 has a bit of oil on the threads as maybe a valve cover gasket leak ?

View attachment 25045

I did have 2 leaking valve covers around 12 months ago, I also had a leaking valley cover around 10 months ago... all of which has been sorted and I fitted a new PCV pipe system plus a new oil pressure switch as that went bad all at the same time .
The new plugs I've put in are all gapped correctly to your above specification (1.1mm).
I honestly can't say how old the plugs that I've taken out have been in the motor... at least 2 years as I've never changed them since I had the car imported from Japan.
The car has gave me no running issues or misfires etc, in the time that I've owned it (apart from when 1 plug lead snapped in half! They were the original 20+ year old leads so expected! I fitted a full new set of silicone double thick leads earlier this year ).

Car runs as good as it did before I did the plugs
Can't complain

 

[teamzr1]

OK, that answers why there was some oil on the threads
The old plugs look like the gap was like 0.70 to 0.80 is way too much and yes 1.1mm or 0.43 is good gap

Too bad you did not post about when replacing the valley pan as I would have suggested replacing both knock
sensors as they degrade which are recessed and water from like washing engine runs down what sensors out and screws them up

I suggest if changing them to take some silicon and build a dam around both holes, so water cannot flow down there

 

[Krusty]

OK, that answers why there was some oil on the threads
The old plugs look like the gap was like 0.70 to 0.80 is way too much and yes 1.1mm or 0.43 is good gap

Too bad you did not post about when replacing the valley pan as I would have suggested replacing both knock
sensors as they degrade which are recessed and water from like washing engine runs down what sensors out and screws them up

I suggest if changing them to take some silicon and build a dam around both holes, so water cannot flow down there

I had the valley gasket replaced at a local and recommended by this group American car specialist (Parts USA in Bredbury). They let me do the work with them to allow me to better understand my car (I am professionally motorcycle trained and time served, currently working for Kawasaki. Worked on cars also on and off over the years and I've worked on all of my own JDM cars. They understood that I wanted to just learn more about my Corvette from the people that do it professionally also... a great bunch of lads). Anyway, they did a very thorough job with regards to the valley gasket change, cleaning out any contaminants and stains along the way. They inspected the condition of my knock sensors and retorqued everything as it went back together. They also helped me find the exhaust squeaking that I had issues with locating (if you remember from a post >12 months back) whilst it was on their premises. They have also fitted a new front timing cover because mine was cracked when I purchased the car nearly 2 years ago, a new seal, a Summit pulley and pinned my crank also. I'm really happy with everything they've done for me so far, and they offer a substantial discount to club members.
My car is dry stored also and very rarely gets 'washed' because I only ever use it on nice, sunny, dry days hahaha. It only ever needs a good wipe down after each drive and a fresh polish every now and then. Maybe 3-4 times a year it gets a really good wash... it's just a nice toy for me.
I would never wash the motor either! with working on motorcycles my whole life, I see first hand almost daily the damage caused by pressure washing motors and electrical components
But if I ever do end up back under the valley pan, I will most certainly change them and apply silicon as you've suggested. Prevention is better than a cure as they say