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Ultimate Opel Spark Plug

26K views 97 replies 32 participants last post by  Autoholic 
#1 · (Edited)
I had read in a thread here that the “best” ultimate spark plugs for our engines was:

NGK Iridium BPR6HIX

And the next best was:

NGK Platinum BP6HVX

So I went to my excellent local auto parts store and they didn’t stock either of them, but they cross-referenced and said that they did have these Denso’s which they said were the equivalent:

Denso Iridium IW20 (5306)(I06) – the last two were other designators on the box.

I have a high energy MSD ignition system and I wanted to increase my plug gap because of this, so why not upgrade the plugs at the same time. They came with .040” gaps which suited me just fine. My previous plugs had less than 5000 miles, but had weathered all my timing, carb, and upgrade adjustments since I’d gotten the car 5 years ago, so a clean slate with the best possible new plugs seemed warranted. My old plugs(which were the correct light brown color, indicating that my air/fuel ratio was in the proper range), gapped at .030-.035”, were:

Champion RL95YC

I put the new plugs in and they work just fine. I’ve only driven a low speed 10 miles with them. I seem to idle a bit faster and run a tad smoother, which seems to indicate that I’m burning gas more efficiently. I noticed that the threaded part of the new plugs was ¼” longer than the Champions and I felt them “push through” some built up deposits, where the previous plugs had reached their insertion limit, while installing them. They performed as advertised so I was happy.

Then that darn Mike Notigan emailed me with concern that plugs that were too long would affect my wave fronts and eventually give me trouble with hot spots from carbon build up and such. Dang him! Dang him to heck! My initial euphoria was popped like a bubble gum blow out all over my face.

I had a spare unrestored 2.0 head in the basement, so I just got done installing both plugs to see what we shall see. Yup, the new plugs stick a whole ¼” into the combustion area. Below are pics.

So my question is: Is this totally unacceptable? I should return them, right? They probably increase my compression a little(Wheeeee!). Should I keep them?

Would the NGK Iridiums listed above have been the proper length?

Please help me out in obtaining the “ultimate plug” for street use in a moderately jacked up 2.0 engine.





 
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#5 ·
just posted in the other thread...

Just to wrap up my end of this thread hijack, I got some iridium Denso's that are supposed to be the equivalent of the recommended "best" choice NGK iridiums. They came already consistantly gapped at .040". The previous champions I had ranged in gap from .030" to .035". The threaded part was about 1/4" longer and I feared they might hit the pistons, but the car made it to the show and back, so I guess I'm good t'go!
You should grind the last 1/4" of threads off the plugs then.

Why? Well, in 10,000 miles or so those threads will be so carboned up, you may never be able to remove them from the cylinder head.



 
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#6 ·
I just found a cross-reference chart at this location:

DENSO SPARK PLUGS

It appears that the parts store should have given me IWF20 plugs, instead of IW20's. Those appear to have been spec'd for the Isuzu Opels.

I'm cool with grinding them down and I see that Bob deemed it worthy of his time to grind and polish a "too long" plug to Hubble telescope mirror brightness.

Am I to take it that this is a cool, rad, or otherwise gnarly thing to do?

Did the RallyBob Institute of CIH Overengineering and Endless Research find that doing this improves performance?

The store will probably take them back, shouldn't I just get the proper length plug?
 
#7 · (Edited by Moderator)
It appears that the parts store should have given me IWF20 plugs, instead of IW20's. Those appear to have been spec'd for the Isuzu Opels.

The store will probably take them back, shouldn't I just get the proper length plug?
The store SHOULD take them back, it's their fault not yours!
 
#8 · (Edited)
I never looked at this when I had my 1.5 head off the block........I know the 1.5's combustion chamber is much smaller. I dont remember the plugs being that far in. do I need to bother doing this? I bought the long NGK plugs just for this reason if memory serves. I guess I could always pull a plug out and try it on the "other" 1.5 head and see, but the one on the car is slightly ported and it wouldnt be "exact".
Joe
 
#9 ·
Well, just to throw another plug on the "pile", here's one that another member found through a NASCAR friend of his. I have used these in my car, but, just for short runs till I could find someone to give me a definitive answer to whether I can leave them in. They clear with no problem in a 1.9 head, I just don't know about the heat range. These are not readily available, and they're not cheap either:shocked:
 

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#12 ·
There are a lot of errors present in the databases of auto part stores when it comes to Opels, even more now than there used to be because of keyword searching.

There is also an error in how a conclusion was reached of how a particular spark plug would perform. It's not unusual that a brand-new part slightly altered might improve performance during its initial drive. You can achieve a bit faster and smoother idle by simply advancing your distributor a few degrees, but that's not a good thing as you would also increase your chances of premature detonation and lose some higher-RPM acceleration when you do that.

The big mistake is not only making a conclusion following a short drive but then "reporting" it here as if that's a universal fact. Shouldn't a more measured or a longer-term evaluation be performed before a thread is started with a title like "Ultimate Opel Spark Plug"? Has a desire for the immediate gratification of participation in social media now eclipsed old-school concepts like disciplined application of a scientific method, particularly when the information advocates other Opel owners to install insufficiently tested parts in their engines?
 
#17 ·
I believe that many of our motors have had some sort of modification in one way or another. Due to the fact of such variances in one motor to another, the ONLY way to test different spark plug brands and such would have to be performed on a BONE STOCK engine to get a starting point and then applied to ones own motor depending on modifications. Sound Good??? Ok... Now... who's got a BONE STOCK motor we can start the testing with??
 
#24 · (Edited)
FWIW, over the years I have tested every plug I could get my hands on on multiple engines. I did find that the Bosch Platinums worked very well on bone-stock engines. As in points/condensor/stock coil.

But they sucked for use with a stronger ignition.

I now use NGK's or Torquemaster's (modified Bosch copper) exclusively for performance and racing applications. The spark kernal energy of the Torquemaster's with a good ignition is ridiculous...I think you could weld with them. But I emphasize the fact that you need to be able to supply the voltage to the plugs to gain the advantage.
 

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#18 ·
That's enough discussion about not discussing stuff. :no:

I want to learn something from this thread. :yup:

I'm curious about the concept of using plugs that PROTRUDE into the combustion chamber. I can see potential pros and cons to this. These are entirely layman's guesses and by no means should be taken as definitive conclusions. They are merely points for discussion.

Pros:
Spark occurs closer to the center of the air/fuel column entering the combustion chamber. Possibly less chance of the air/fuel mixture not igniting because the spark normally occurs so close to the wall of the combustion chamber.

Cons:
The plug will get a LOT hotter being surrounded by more flame. Possible interference with the in and out flow of gasses during the cycle. Possible wave front interruption. The risk of a too long plug hitting the piston.

Thoughts on these points and my original questions? :veryhappy
 
#23 · (Edited)
Well, my theory is based on my experiences with the 1.5 and 1.6 heads.

For those that don't know, those heads required a .750" reach plug from the factory, due to the smaller combustion chamber and therefore thicker combustion chamber walls. I have found that these so called 'small chamber' heads always had better combustion properties than the bigger chamber heads (1.9, 2.0, 2.2, 2.4), which all use a .460" reach spark plug.

Now part of that better combustion is no doubt due to higher compression, and part of it due to the smaller chamber itself (flame travel speed matters less when you have a shorter distance to travel).

But in thinking about it, I realized that part of the improvement may be from the fact that the spark plug protrudes 1/4" closer to the center of the chamber (ever notice most new engines have the plugs dead-center in the chambers?). As well, due to the angle of the plug in the head, the plug also protrudes a little bit lower in the chamber, closer to the piston.

It was my intention to test short plugs and long plugs back-to-back on a chassis dyno to either prove or disprove my theory, but my friend's shop that had the dyno closed up. They were 12 minutes away from my shop previously, the new owners of the dyno are 2 hours away!

My only concerns with the long plugs are that they:

1) Won't work with domed pistons due to the potential for contact.
2) Will get carbon buildup on the threads, hence the removal of the last 1/4" of thread.
3) With the threads intact, there will be multiple hot spots and potential melting of the threads under high loads.
4) Not sure if a colder heat range is required, since the longer plug is not having all that combustion heat absorbed by 100% of the threads.

I would have figured all this out with dyno testing, but never got the chance.
 
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#20 · (Edited by Moderator)
Ok... Now... who's got a BONE STOCK motor we can start the testing with??
I do, send all your test parts to me. Lets start with some side draft carbs!!

Pat
 
#25 · (Edited)
Cutting down the threads...

BTW, I made a simple fixture to remove the threads on these longer plugs. Used a thick scrap of steel and tapped it to match the plug threads (14 mm x 1.25 pitch), then chucked the spark plug in a hand drill whilst sanding the threads off with a small 2" disc grinder.

Once that was done, I threw the plug in my drill press and used some 150 grit paper, 240 grit paper, and Scotchbrite to smooth things out. Total time: 3 minutes.
 

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#34 · (Edited)
BTW, I made a simple fixture to remove the threads on these longer plugs. Used a thick scrap of steel and tapped it to match the plug threads, then chucked the spark plug in a hand drill whilst sanding the threads off with a small 2" disc grinder.

Once that was done, I threw the plug in my drill press and used some 150 grit paper, 240 grit paper, and Scotchbrite to smooth things out. Total time: 3 minutes.
Now THAT's what I call thinking outside the box! :yup:

Now, to 'throw another log onto the fire', anyone tried any of Bosch's multi-electrode (2, 4) plugs, all of which were .750" thread reach, i.e. too long?

Personally, I still use Bosch's non-resistor, copper-core standard heat-range plugs with modified ground electrode in all of mine . . .



. . . honestly don't know if you can still buy them. Bought enough of them at 97 cents apiece in standard and one range colder years ago to last for my needs though.
 
#28 ·
@ Gordy- I already see a LOT of good info here. I have already have learned a thing or two.

@ Bob- I agree on the BOSCH Plats, if you're going to keep the system stock, they're great. The wife's stock 74 Sportwagon has them, and they allow the car to be started easily at anytime or weather. Hit the gas pedal twice, turn the key and she's alive.

Also, I should have added in my previous post, I am NOT currently running the NASCAR plugs in my Sportwagon. As stated and clarified by Dan, that the plugs are cold. When I say "short runs" I mean I have run them a day or so in normal driving, not out on the Hwy.

Now, if testing wanted to be done, I have two stock motors here, one is a weber'ed 74, the other is a 75 F.I., both are running Pertronix.
 
#29 ·
Iridiium spark plugs and MSD-Jacobs Hi Energy Ignition: Thoughts/Comments?

All,
Long ago I installed a Jacobs hi-energy ignition system in my 86 Fiero GT. The company recommended Copper Core plugs only and to experiment with the plug gap until the desired combination of light tan on porcelain along with smooth engine operation is achieved; being that the high voltage is going to waste if the factory plug gaps are used. To take advantage of the bright kernel of voltage that these ignition systems can deliver, the plug gap must be opened in .005 inch increments...

The following link from MSD states to not use an iridium plug with the MSD; the same info I recall from my Jacobs system.: Best sparkplugs + MSD 6AL - MSD Tech Support Forums
I'd like to hear what our experienced folks on this site have to say about using iridiums with these aftermarket high energy ignition systems. As for me, I'll stick with my Bosch Platinums with my XR 700 electronic ignition. (Note: tried using anti-oil fouling spark plug extenders with the platinums but something interesting occured which made me remove them.....oh, my engine is a bit worn which explains my attempted use of the anti oil fouling plug extenders.......next stop are the JC Whitney Engine Rebuild Tablets!!:yup::haha::veryhappy....that's another topic for another thread.......
Take Care,
Mike
 
#39 ·
All,
Long ago I installed a Jacobs hi-energy ignition system in my 86 Fiero GT. The company recommended Copper Core plugs only and to experiment with the plug gap until the desired combination of light tan on porcelain along with smooth engine operation is achieved; being that the high voltage is going to waste if the factory plug gaps are used. To take advantage of the bright kernel of voltage that these ignition systems can deliver, the plug gap must be opened in .005 inch increments...
I used to run the Jacobs in my supercharged Toyota pickup truck. I ran the plug gap at .055" with 9 psi of boost. No problem lighting the plugs off!
 
#30 ·
Well, golly, now I'm all confused. Mike had sent that link to me before and I admit to not having read it, but I read it this time. The MSD techy is pretty darn definitive about not using "fancy" plugs, just copper ones rated a step or two colder. It seems that the skinny wire iridiums are a big no-no.

I can't make heads or tails of plug charts. It's unbelievable how many types of plugs there are.

So now I need a good quality copper plug that's a step or two cooler than stock. Can anyone decypher the charts and recommend an appropriate plug?
 
#31 · (Edited by Moderator)
So now I need a good quality copper plug that's a step or two cooler than stock.
The CD unit multi fires during the burn time.
Not the firing voltage!

A good plug to start with is a autolite 63.
Read the ground electrode to fine tune the heat range.
The ground electrode should turn color around 2/3 of the way to the shell.
Disclaimer: I've got a pretty good idea of Gordon's setup! If you're not comfortable monkeying with your car, DON'T!
 
#33 ·
#35 ·
how about making a collar 1/4" long that threads on to plug, could be tapered to match plug if needed or add compression washer, add a little exhaust compound and have the plug tip in the right spot with no threads showing ?
 
#79 · (Edited)
I'm gonna bump the above idea. No one talked about it.

As for the temperature range of a spark plug, it has to do with the ceramic insulator. The hotter a plug, the less ceramic insulator there is to serve as a heat barrier, exposing the electrode to heat quicker. It has nothing to do with the ability of the spark plug's spark itself, and more to do with melting the plugs / pre-ignition or fouling. Engines that are used in high performance applications run colder plugs because racers don't want to destroy their engine when the plugs get so hot, that they pre-ignite the fuel. If two plugs of identical design except their temperature rating are used, the spark will be the same. The temperature of the plug would only impact fuel economy if the temperature of the plug wasn't correct for the application, causing the plug to foul from carbon build up (bad spark, misfire) or overheat (pre-ignite). I believe I communicated all this correctly, it's been a long day. :)
 
#37 · (Edited)
In what uses would someone use a hotter plug or a colder plug? What types of set-ups benefit a hot plug/cold plug? Will using a colder or hotter plug when its not called for cause any issues/damage?
If you are running a much more powerful engine than stock (very high compression and higher rpms), if you have a turbo, if you have a supercharger, or if you are running nitrous oxide...you need to run colder plugs. Otherwise you can literally melt the stock plugs.

The down side to a colder plug on a not-so-high performance engine is that they can foul out fairly easily, especially during start up and with idling or puttering around town. Many race vehicles are started with hot plugs, run up to operating temperature, then shut off and colder plugs installed before a race.

If you have a low compression engine that is seldom run hard, has a lot of mileage (worn out), and is primarily used in town (lots of stop and go), you can possibly go with hotter plugs than stock. A hotter plug will fire off easier in the cold, will tolerate being idled for long periods of time, works well with a weaker ignition, with a rich mixture, or with an oil burning engine. But a hotter plug should never be used for 'autobahn' type conditions.
 
#41 ·
RockAuto

I ordered my last several sets of spark plugs, including non-Opel, from RockAuto. They were significantly less expensive than buying them locally at AutoZone, O'Reilly, or NAPA. You have to sort out the shipping charges from RockAuto, as they ship from different warehouse locations. Several times my parts were drop shipped from a local California warehouse and arrived quickly. :veryhappy
 
#45 ·
I could be waaaay out of my league here, but, I would think the longer plugs would act much like a hemispherical head and generate a flame front that creates a more even force across the surface of the piston thus acting directly against the crankshaft. If the plug reach were shorter, the flame front would "wash" like a wave across the surface of the piston. The flame "wash" might not be a bad scenario either since that might help the engine breathe better, depending on the design. I'm thinking cross flow heads here.

And I would think you would want your spark plug in the way of the air fuel mix so when the spark comes its not hidden away in a remote corner of the combustion chamber, but is in the thick of the mix that needs igniting!

My only problem is the longer plug takes up room that could be more air/fuel mix.

Lastly, Bob, thanks for the pics and explanations. Awesome stuff. Would you PLEASE compile all your posts off this site and write a book?
 
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