AC Owners Club Forum > AC Weller Engine

Spark plugs

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mmouss:
Hello, I thank you for admission on this interesting forum. :)

I recently bought a 1936 AC 16/80 and am wondering if the sparks plugs fitted are the correct type.
Those are NGKs B6HS and tend to get wet quite often.

I think of fitting slightly hotter ones like NGKs B5HS or equivalent Champions L86C but would of course avoid the risk of damaging pistons…

Can someone give me an advise about this please?

mmouss:
Hello again,

So, nobody here has plugs on his AC engine and can help with advise about them??? :-[

Flyinghorse:
Yes surprised you had no response.
The 2 litre saloon runs this engine and there’s a good website that details engine / ignition maintenance and Leo Archibald wrote a good book on the 2 litre car  that has a engine / gearbox section - I would get a copy as it covers engine/ gearbox.
http://www.ac2litre.com/maintain4.html

The excerpt from the  site says lodge C14. These may be hard to get but if it were me call up Tim Green. My quick research suggests an equivalent is Ngk B5 which is hotter.
https://www.gsparkplug.com/
 and discuss equivalents( and your issue)  with him. Incidentally many are starting to use iridium plugs now to combat many plug related issues ( wetting) (ace Bristol, CRS )
“Spark-plugs are specified in the manuals as Lodge C14, 14mm. The gap is specified as 0.015 to 0.018 inch (0.38 to 0.46mm). When low octane 2 star petrol was phased out in the UK (in 1989), I found that slight mis-firing occurred on partial throttle, and I followed advice of another classic car owner to widen the spark-plug gap. With a gap of about 0.025 inch (0.64mm) the trouble was solved.”

Hope that helps.
Graham

mmouss:
Thank you very much Flyinghorse for your kind answer.
The link you provided seems very interesting to me as many other important points are also detailed.

I will try Champion L86C which is equivalent to NGK B5 and let you know the result.
I am not sure iridium plugs would be of great help but I will try the 0.025" gap you suggest.

Thank you for your help :)
Michel

administrator:
A bit of a late reply, but I'm using Champion D9, which seem to work well.  I was previously using NGK AB-6, which didn't like a combination of hot weather and stale petrol.

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