| hoghead |
Tue Oct 06, 2009 8:46 am |
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I have seen 12mm spark plugs installed in welded and tapped holes in an attempt to reduce cracking between big valves and the plug.
Is this helpful and if so would 10mm plugs be better? |
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| The Noof |
Tue Oct 06, 2009 1:15 pm |
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| The drop from 14mm to 12mm leaves plenty of material.Nothing to be gained by going any smaller for most apps. |
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| SRP1 |
Tue Oct 06, 2009 6:39 pm |
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In short yes.
If your going to go to trouble might as well go to the 10mm thread, I do.
Should a "situation" occur where you loose a thread it's easy to tap to 12mm and continue on down the road without worry of the area becoming to thin also.
Not to mention the fact that getting a socket in there that fits the smaller plug is a piece of cake if you are running large manifolds...... :D |
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| hoghead |
Tue Oct 06, 2009 7:27 pm |
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| What part number for the 10mm plug do you use and what are your conditions - IE ambient temp, usage, and engine combo |
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| hoghead |
Fri Oct 16, 2009 4:02 am |
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| anyone? |
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| BFB |
Sat Nov 06, 2021 9:39 pm |
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thought this was interesting and thought I'd resurrect it,
any thoughts? |
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| Igpoe |
Sun Nov 07, 2021 4:13 am |
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| If ignorance is bliss I should be happy right now |
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| Bad bug |
Sun Nov 07, 2021 4:36 am |
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| Look at bike plugs. Jake Raby used 10mm plugs in his dual plug T4 heads if he will chime and help out with what work in 10mm plugs for the aircooled engine that would be help you out tremendously.[/s] |
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| gears |
Sun Nov 07, 2021 6:44 am |
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When deeply flycutting the heads, only 10mm will fit in the lower position.
12mm upper, 10mm lower plugs
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| raygreenwood |
Sun Nov 07, 2021 8:08 am |
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As others have mentioned.....a simple method might be to start at a motorcycle shop. You might get lucky in 5 minutes!
However......the best way is to patiently sit down at your computer.....pull up the NGK, Bosch and Denso spark plug chart......and start "building" spark plugs by their letter codes and search on each one. Open a work document.to record what letter/number codes correspond to something in production.
Here is a blog post from a dude with a twin plug motorcycle who also is posting about the spark plug chart.
https://tro.bike/digitools/motorcycle-spark-plugs-ngk/
By the way.....the chart in the blog is not just a motorcycle plug chart. But alao be aware.....and NGK is worse than Bosch about this...NGK has about a half dozen chart designs on line ...that all work but have more or less information.
Also study up on the electrode types, metal combinations and what their design is meant for. Just because a plug has some sort of exotic metal for some specfic application.....doea not mean that it cannot be used on your engine and does not have benefits for your set up.
Knowing what else "CAN" work....can give you a wider range of choices.
Just going off of the NGK chart in that link .....for example......I would start "BUILDING" a plug part # to search on like this:
C= 10mm plug diameter
C= 5/8" hex
P= projected insulator
R= resistor
6= heat range
E= 19mm reach
G= fine wire nickle allot center electrode
CCPR6EG.......like that. The last letter.....there are several in that long list that you might find plugs for that seem alien to you that may work just fine.
Lastly.....do not do what the dude in that,thread did. If you buy iridium plugs.....DO NOT gap them. Iridium is VERY brittle and fragile. There are very few people in these forums that can gap an iridium plug.....reliably and safely.....with any guarantee of not cracking or chipping the center electrode.
They are gapped at the factory by a special tool that has "0" contact with the center electrode.
Yes.....anyone can make a hook tool to bend the side ground electrode away from the center electrode to open the gap.....and its easy with a delicatd touch and some practice to tap the ground electrode back inward to reduce gap......which by the way is how both Bosch and NGK direct you to adjust gap.......on any electrode type EXCEPT iridium, Reuthenium and fine wire center electrodes.....so thats not the issue.
The issue is that MEASURING the gap is what damages it. Decide what gap you need and buy them with that gap.
Ray |
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| Lo Cash John |
Sun Nov 07, 2021 3:51 pm |
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| There even used to be 8mm spark plugs back in the 60’s. I have no idea if those are still available. |
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| raygreenwood |
Sun Nov 07, 2021 7:15 pm |
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Lo Cash John wrote: There even used to be 8mm spark plugs back in the 60’s. I have no idea if those are still available.
Yep!
https://www.summitracing.com/search/brand/ngk-spar...versal/yes
Ray |
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