Is A6 really the right plug for an AD ??

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pistnbroke
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Joined: Fri Aug 22, 2008 11:06 pm
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Is A6 really the right plug for an AD ??

Post by pistnbroke »

Went to my local small parts shop and they had a box of A6 plugs ...wow
But on screwing it into the head ( off motor ) the electrodes were well up inside the treads.. This is bad as the electrodes should be exposed to the new charge of fuel in the cylinder ...so is this a true substitue or just the best we can get that works ?? dont tell me there is no clearence as there is at least 8mm between the head and piston at this point.
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charlesp
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Post by charlesp »

You're right, the threaded portion gives every impresswion of being too short. Same with the earlier short water jacket 102s

But they seem to run all right, and I am not aware of a plug that is that little bit deeper, as it were, with everything else the same.

The 8 COM Champion wasw the one recommended at the time, with the Lodge CI as an alternative. They are both identical in depth to the A6, if I recall correctly.
pistnbroke
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Post by pistnbroke »

since made more checks ...thread is 13.5mm and there is another 13mm before you hit the piston ...considering the engine struggles to develop even 1 HP you would think having the electrodes in the right place for the progress of the flame front through the mixture would be important ...Will see what I can find ...should be a taper seat available and then take the taper off on the lathe ...If its NGK with a 6 should be OK and it will put the compression ratio up a bit !!!
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Since stuck the plug in the lathe and taken about 3mm off the mounting flange ....however either the thread is not fully formed at the end in the head or its corroded /damaged as the plug is a bit tight...anyway its not up a side alley now but in the combustion chamber !!
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