Denso Plugs (Japan)???
09-21-2013, 11:34 PM
#1
Melting Slicks
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St. Jude Donor '11-'12-'13,'19-'20
Denso Plugs (Japan)???
So I bought my 01 coupe in April 12 with 32k. Purchased from second owner who had all the original docs and maintenance records. Changing of plugs and wires was not listed, and with 100k recommendation why would they, right?. I have 43k on her now, and after 12 years I decided it was time, if nothing else due to age. I bought Champion Iridiums and MSD red wires from GMPARTSHOUSE and went at it today. Other than #8 PIA everything went pretty smooth. Several of the OEM wires crumbled at the base of the boots while being extracted so it was definitely time for them to go. When I pulled the first plug I was really kind of shocked to find this Denso (Japan) part. WTF??? 
Fully expecting AC-Delcos!!??? Did they put these in at the factory?? I never even heard of a Denso???. Please dont tell me they are a leading brand used in Toyots and Nissans?!?!? 
Anyway these plugs also showed visible wear although not wasted by any means. Glad I got them out of there though!
.. I dont know why its bugging me so much...just hoping someone changed them and they weren't installed in the factory...but I fear that is false hope! 
Fully expecting AC-Delcos!!??? Did they put these in at the factory?? I never even heard of a Denso???. Please dont tell me they are a leading brand used in Toyots and Nissans?!?!? Anyway these plugs also showed visible wear although not wasted by any means. Glad I got them out of there though!
.. I dont know why its bugging me so much...just hoping someone changed them and they weren't installed in the factory...but I fear that is false hope!
09-22-2013, 12:00 AM
#3
Race Director
denso is the OE plug in the z06 should have a number like 12563707 on it
probably the best spark plug manufacturer in the world, well, toss up between them and NGK
the quality control at denso and materials used are absolutely top notch. the new ac delco 41-110 plug has either directly copied the denso electrode design or IS using denso parts to assemble the plugs
remember delco often has various manufacturers make their parts and denso is one of the largest OE suppliers on the planet
their aftermarket gear is also stellar. it performs and doesn't easily fail.
it's almost funny to me that you would question denso and then use the words "msd wires" in the same sentence
probably the best spark plug manufacturer in the world, well, toss up between them and NGK
the quality control at denso and materials used are absolutely top notch. the new ac delco 41-110 plug has either directly copied the denso electrode design or IS using denso parts to assemble the plugs
remember delco often has various manufacturers make their parts and denso is one of the largest OE suppliers on the planet
their aftermarket gear is also stellar. it performs and doesn't easily fail.
it's almost funny to me that you would question denso and then use the words "msd wires" in the same sentence
Last edited by racebum; 09-22-2013 at 12:03 AM.
09-22-2013, 02:21 AM
#4
Drifting
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denso is the OE plug in the z06 should have a number like 12563707 on it
probably the best spark plug manufacturer in the world, well, toss up between them and NGK
the quality control at denso and materials used are absolutely top notch. the new ac delco 41-110 plug has either directly copied the denso electrode design or IS using denso parts to assemble the plugs
remember delco often has various manufacturers make their parts and denso is one of the largest OE suppliers on the planet
their aftermarket gear is also stellar. it performs and doesn't easily fail.
it's almost funny to me that you would question denso and then use the words "msd wires" in the same sentence
probably the best spark plug manufacturer in the world, well, toss up between them and NGK
the quality control at denso and materials used are absolutely top notch. the new ac delco 41-110 plug has either directly copied the denso electrode design or IS using denso parts to assemble the plugs
remember delco often has various manufacturers make their parts and denso is one of the largest OE suppliers on the planet
their aftermarket gear is also stellar. it performs and doesn't easily fail.
it's almost funny to me that you would question denso and then use the words "msd wires" in the same sentence
09-22-2013, 03:43 AM
#5
Melting Slicks
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St. Jude Donor '11-'12-'13,'19-'20
denso is the OE plug in the z06 should have a number like 12563707 on it
probably the best spark plug manufacturer in the world, well, toss up between them and NGK
the quality control at denso and materials used are absolutely top notch. the new ac delco 41-110 plug has either directly copied the denso electrode design or IS using denso parts to assemble the plugs
remember delco often has various manufacturers make their parts and denso is one of the largest OE suppliers on the planet
their aftermarket gear is also stellar. it performs and doesn't easily fail.
it's almost funny to me that you would question denso and then use the words "msd wires" in the same sentence
probably the best spark plug manufacturer in the world, well, toss up between them and NGK
the quality control at denso and materials used are absolutely top notch. the new ac delco 41-110 plug has either directly copied the denso electrode design or IS using denso parts to assemble the plugs
remember delco often has various manufacturers make their parts and denso is one of the largest OE suppliers on the planet
their aftermarket gear is also stellar. it performs and doesn't easily fail.
it's almost funny to me that you would question denso and then use the words "msd wires" in the same sentence
The parts I bought were recommended by one of the most widely loved vendors on this forum. I use MSD wires on my C3 383 and never had a problem so Im not sure what your beef is there. As per my post, I'd never heard of Denso!! Maybe Im an old guy thats been living under a rock whatever, but I pay attention enough to know these are not in north american automotive advertising, unless maybe its in ricer rags, which I don't read. I just thought it was strange they put a clearly marked made in Japan part in a new 2001 Corvette.So you got some data to back up your claim on them being the "best"?? ....and MSD wires being "Bad"?....or is this all just your opinion??
09-22-2013, 04:11 AM
#6
Le Mans Master
I personally have never used MSD wires but recently I asked Forum members their experience with MSD wires. I got many replies stating about wire failures from people who used the MSD wires. It could be a contributing factor as to why they have recently filed for bankruptcy. As far as Denso is concerned I have been aware of them for years. They make reliable, quality parts. I believe they even make some components for Harley-Davidson if my memory serves me correctly. I've used the wires from LG Motorsport with good results, they heat insulation woven right into the wires.
09-22-2013, 09:50 AM
#7
Melting Slicks
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St. Jude Donor '11-'12-'13,'19-'20
I personally have never used MSD wires but recently I asked Forum members their experience with MSD wires. I got many replies stating about wire failures from people who used the MSD wires. It could be a contributing factor as to why they have recently filed for bankruptcy. As far as Denso is concerned I have been aware of them for years. They make reliable, quality parts. I believe they even make some components for Harley-Davidson if my memory serves me correctly. I've used the wires from LG Motorsport with good results, they heat insulation woven right into the wires.
I searched and found your thread. More good opinions than bad it seems. Only one critique had any facts (Corrosion after a couple of years) the rest just subjective opinions as far as I can tell. Now that they are installed, I guess I just watch them and form my own subjective opinion! 
As far as the Denso's go, thanks for the info and link to those who provided. I see people criticizing me for not knowing who they are, but also so ZERO recommendations for them in the many "What plug should I use" threads that I found.
Seems the NGK's are the most popular by far, but I got the Champs from GMPARTSHOUSE and also use Champs in the C3. So I go with what I know until they give me reason not too. 
Last edited by CheezMoe; 09-22-2013 at 09:53 AM.
09-22-2013, 01:32 PM
#8
Safety Car
Welcome to living under "rocks" dosoctaves, nice and cool in the shade huh!
We dumb-asses learn new things every day
You ask about Denso plugs.
They are an excellent premium spark plug.
Have used them for years in Australia and here in the USA.
Was first introduced to them 30 years ago when I was an auto mechanic, on all the premium Japanese cars, and high performance ones.
Denso, NGK, etc all produce a quality plug. Spark plugs like everything else have their applications.
Plug wires, time for another myriad of conflicting recommendations ............
We dumb-asses learn new things every day
You ask about Denso plugs.
They are an excellent premium spark plug.
Have used them for years in Australia and here in the USA.
Was first introduced to them 30 years ago when I was an auto mechanic, on all the premium Japanese cars, and high performance ones.
Denso, NGK, etc all produce a quality plug. Spark plugs like everything else have their applications.
Plug wires, time for another myriad of conflicting recommendations ............
09-22-2013, 02:00 PM
#9
Race Director
Thanks striper!! I searched and found your thread. More good opinions than bad it seems. Only one critique had any facts (Corrosion after a couple of years) the rest just subjective opinions as far as I can tell. Now that they are installed, I guess I just watch them and form my own subjective opinion!
As far as the Denso's go, thanks for the info and link to those who provided. I see people criticizing me for not knowing who they are, but also so ZERO recommendations for them in the many "What plug should I use" threads that I found. Seems the NGK's are the most popular by far, but I got the Champs from GMPARTSHOUSE and also use Champs in the C3. So I go with what I know until they give me reason not too.
I searched and found your thread. More good opinions than bad it seems. Only one critique had any facts (Corrosion after a couple of years) the rest just subjective opinions as far as I can tell. Now that they are installed, I guess I just watch them and form my own subjective opinion! As far as the Denso's go, thanks for the info and link to those who provided. I see people criticizing me for not knowing who they are, but also so ZERO recommendations for them in the many "What plug should I use" threads that I found.
Seems the NGK's are the most popular by far, but I got the Champs from GMPARTSHOUSE and also use Champs in the C3. So I go with what I know until they give me reason not too. with myself i remember msd wires leaking energy creating a misfire on an older engine that was leaking a bit of oil. where oil touched the wire you could see blue lights at night
with denso i think about what the OE plugs in my z06 looked like after 10 years, i think about my old turbo honda and i think about my jeep. all were absolutely perfect. same with the denso spark plug wires. perfect clip fit, length, ohms are +- 1% in a set. every part, rather it's an o2 sensor, spark wire, plug or alternator that i've used from denso has been stellar
09-22-2013, 04:36 PM
#10
Team Owner
I'm presently using one of those other "terrible" brands and they work well in my little stocker motor.
09-22-2013, 07:15 PM
#11
Race Director
Not "offered". They were OE on many, if not all C5s; at least for the first several year models. They were OE on my '99 and most of them also had the "missing" pucks that so many complained about when I changed them at about 50-60K.
I'm presently using one of those other "terrible" brands and they work well in my little stocker motor.
I'm presently using one of those other "terrible" brands and they work well in my little stocker motor.
new part number is 5325
they also list another which is 5090
got me what the difference is between those two
i just doubt many people use them when the ac delco 41-110 is only $5.69 shipped via amazon
09-23-2013, 01:28 AM
#12
Melting Slicks
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Strike at GM caused the switch of spark plugs
It was because of a strike, not because Denso was a "better" spark plug. GM started putting them in all (some)GM cars and trucks if the supply of Delco plugs didn't keep up with demand during and after the strike. I remember it well. Read the story:
In 1998, fearing a strike over a $200 million investment that had not materialized, GM began to pull critical dies from the Flint Metal Fab plant on the other side of town, to be shipped to another plant. The UAW workers at the plant immediately went on strike to protest the move. Mostly in response to this, but also because of fears that their own work would be moved elsewhere, workers at Flint East went on strike a week later on June 11, 1998. Since Flint East was the sole source of some parts for almost the entire company, within two weeks, virtually all of General Motors was shut down. On July 28, GM agreed to the investment to Flint Metal Fab and to keep Flint East open until at least 2000. The union agreed to cooperate on efforts to increase productivity at both plants.[5] The strike cost GM an estimated US$2.8 billion.[1]
In 1998, fearing a strike over a $200 million investment that had not materialized, GM began to pull critical dies from the Flint Metal Fab plant on the other side of town, to be shipped to another plant. The UAW workers at the plant immediately went on strike to protest the move. Mostly in response to this, but also because of fears that their own work would be moved elsewhere, workers at Flint East went on strike a week later on June 11, 1998. Since Flint East was the sole source of some parts for almost the entire company, within two weeks, virtually all of General Motors was shut down. On July 28, GM agreed to the investment to Flint Metal Fab and to keep Flint East open until at least 2000. The union agreed to cooperate on efforts to increase productivity at both plants.[5] The strike cost GM an estimated US$2.8 billion.[1]
09-23-2013, 01:42 AM
#13
Race Director
It was because of a strike, not because Denso was a "better" spark plug. GM started putting them in all (some)GM cars and trucks if the supply of Delco plugs didn't keep up with demand during and after the strike. I remember it well. Read the story:
In 1998, fearing a strike over a $200 million investment that had not materialized, GM began to pull critical dies from the Flint Metal Fab plant on the other side of town, to be shipped to another plant. The UAW workers at the plant immediately went on strike to protest the move. Mostly in response to this, but also because of fears that their own work would be moved elsewhere, workers at Flint East went on strike a week later on June 11, 1998. Since Flint East was the sole source of some parts for almost the entire company, within two weeks, virtually all of General Motors was shut down. On July 28, GM agreed to the investment to Flint Metal Fab and to keep Flint East open until at least 2000. The union agreed to cooperate on efforts to increase productivity at both plants.[5] The strike cost GM an estimated US$2.8 billion.[1]
In 1998, fearing a strike over a $200 million investment that had not materialized, GM began to pull critical dies from the Flint Metal Fab plant on the other side of town, to be shipped to another plant. The UAW workers at the plant immediately went on strike to protest the move. Mostly in response to this, but also because of fears that their own work would be moved elsewhere, workers at Flint East went on strike a week later on June 11, 1998. Since Flint East was the sole source of some parts for almost the entire company, within two weeks, virtually all of General Motors was shut down. On July 28, GM agreed to the investment to Flint Metal Fab and to keep Flint East open until at least 2000. The union agreed to cooperate on efforts to increase productivity at both plants.[5] The strike cost GM an estimated US$2.8 billion.[1]
must have been one long strike
let's see here...ahhh Section 6-76 Corvette Specs..............STANDARD plug for Zo6, Denso PTJ16R15
the strike might of had something to do with why it started in the 90s but they never changed back.
Last edited by racebum; 09-23-2013 at 01:47 AM.
09-23-2013, 03:19 AM
#14
Pro
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denso is the OE plug in the z06 should have a number like 12563707 on it
probably the best spark plug manufacturer in the world, well, toss up between them and NGK
the quality control at denso and materials used are absolutely top notch. the new ac delco 41-110 plug has either directly copied the denso electrode design or IS using denso parts to assemble the plugs
remember delco often has various manufacturers make their parts and denso is one of the largest OE suppliers on the planet
their aftermarket gear is also stellar. it performs and doesn't easily fail.
it's almost funny to me that you would question denso and then use the words "msd wires" in the same sentence
probably the best spark plug manufacturer in the world, well, toss up between them and NGK
the quality control at denso and materials used are absolutely top notch. the new ac delco 41-110 plug has either directly copied the denso electrode design or IS using denso parts to assemble the plugs
remember delco often has various manufacturers make their parts and denso is one of the largest OE suppliers on the planet
their aftermarket gear is also stellar. it performs and doesn't easily fail.
it's almost funny to me that you would question denso and then use the words "msd wires" in the same sentence
I'm surprised the OP never heard of Denso products, used on various hi end vehicles and NGK is also Japanese.It's OE on my C5Z and '11 Lexus RX 350.
It's a global economy, the OP maybe surprised that there are parts on the C5 from many international suppliers and what is wrong with
Toyota's (Lexus's) or Nissan's (Infinity's)?
Last edited by tak06; 09-23-2013 at 03:27 AM.
09-23-2013, 03:55 AM
#15
Burning Brakes
Denso makes TONS of automotive products. AC compressors, filters, spark plugs, o2 sensors, fuel injectors, fuel pump, coils, MAFs, etc etc. And BTW, you beloved Champion plugs are made in Mexico, as are the AC Delcos.
The reason the NGK TR55s are always the recommended plugs is because they're cheap, easy to find, and generally good quality. They've been hyped up a bit and now everybody's on the band wagon. I use them as well. But realistically, any plug you buy at the part store, as long as it's not defective and it's gapped properly, will run the same in the car. I've run NGK, Bosch, Champions, Autolite, and AC Delco in a variety of cars, and they're all operate the same. Maybe longevity will differ slightly, but not by any significant amount IMO. Plugs are cheap and easy enough to change that a few thousand miles here and there doesn't bother me much.
My $0.02.
The reason the NGK TR55s are always the recommended plugs is because they're cheap, easy to find, and generally good quality. They've been hyped up a bit and now everybody's on the band wagon. I use them as well. But realistically, any plug you buy at the part store, as long as it's not defective and it's gapped properly, will run the same in the car. I've run NGK, Bosch, Champions, Autolite, and AC Delco in a variety of cars, and they're all operate the same. Maybe longevity will differ slightly, but not by any significant amount IMO. Plugs are cheap and easy enough to change that a few thousand miles here and there doesn't bother me much.
My $0.02.
09-23-2013, 07:32 AM
#16
Team Owner
But realistically, any plug you buy at the part store, as long as it's not defective and it's gapped properly, will run the same in the car. I've run NGK, Bosch, Champions, Autolite, and AC Delco in a variety of cars, and they're all operate the same. Maybe longevity will differ slightly, but not by any significant amount IMO. Plugs are cheap and easy enough to change that a few thousand miles here and there doesn't bother me much.
My $0.02.
My $0.02.
I completely agree.
09-23-2013, 08:04 AM
#17
Drifting
In my previous life as motorcycle mechanic (20 years) I have installed literally tens of thousands of NGK plugs with not one failure.
The first Champion plug I ever touched, literally fell apart when I put a wrench on it. The insulator crumbled off the electrode. It was not uncommon for Champion spark plugs to be bad right out of the box. The gaps were certainly something that needed to be set. The gaps on NGK plugs were usually very close or spot on as delivered.
I wouldn't use a Champion plug in anything but lawn equipment.
The first Champion plug I ever touched, literally fell apart when I put a wrench on it. The insulator crumbled off the electrode. It was not uncommon for Champion spark plugs to be bad right out of the box. The gaps were certainly something that needed to be set. The gaps on NGK plugs were usually very close or spot on as delivered.
I wouldn't use a Champion plug in anything but lawn equipment.
09-23-2013, 08:53 AM
#18
Racer
In my previous life as motorcycle mechanic (20 years) I have installed literally tens of thousands of NGK plugs with not one failure.
The first Champion plug I ever touched, literally fell apart when I put a wrench on it. The insulator crumbled off the electrode. It was not uncommon for Champion spark plugs to be bad right out of the box. The gaps were certainly something that needed to be set. The gaps on NGK plugs were usually very close or spot on as delivered.
I wouldn't use a Champion plug in anything but lawn equipment.
The first Champion plug I ever touched, literally fell apart when I put a wrench on it. The insulator crumbled off the electrode. It was not uncommon for Champion spark plugs to be bad right out of the box. The gaps were certainly something that needed to be set. The gaps on NGK plugs were usually very close or spot on as delivered.
I wouldn't use a Champion plug in anything but lawn equipment.
09-23-2013, 11:07 AM
#19
Melting Slicks
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St. Jude Donor '11-'12-'13,'19-'20
I have always used either Champion or AC-Delco. I'll have to write off my non-familiarity with denso as being sheltered all my performance car experience prior to this C5 was classic Chevy stuff and that is the hobby I follow for the most part. Thanks for all the replies.
I'll keep my eye on the MSD's. As previously stated the densos were visibibly worn with 43k on them. While age certainbly factored into the brittle wires, not relevant to plug wear. And I will comment that after changing these the car is noticeably smoother and more repsosnsive. Took a 125 mile trip into town to visit friend in the hospital yesterday. DIC avg MPG went up from 21.6 to 22.4. it's never been >22 before. So far so good! One correction I will make to my OP, is that I purchased the plugs and wires from ZIP. not GMPARTSHOUSE.
peace!
09-23-2013, 12:33 PM
#20
Burning Brakes
On behalf of the OP, I too at the age of 74 and having a long time experience with stock car racing and backyard auto repair have never heard the name "DENSO" in my life.
My $,02
Fred
My $,02
Fred