Joined: Aug 2022 Posts: 149 Threads: 27
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Location: Cheshire
Car type: Austin 7 RN - 1932
Being of an adventurist nature - I decide it was time to change the spark plugs on my RN Box.
The plugs fitted are NGK AB - 6. Our heritage suppliers seem to offer Champion D16 or D21. Does anyone know the difference between these two??
I had a hunt around the tintterwebs and found an Accuspark AA77C which the British manufacturer says is equivalent to the Champion D16 and is listed for A7 and some bigger Austins. SO I decided to purchase a set. They are 18mm plugs so that is a good start. But my 50 year old plug socket (13/16 inch) went straight on the old NGKs and the Accuspark plugs appear to need a 7/8inch spanner.
More concerning is that the Accuspark plug's reach (washer to tip of the 3 electrodes) is a good 2mm more than the old NGKs.
1. Has anyone had experience of these Accuspark plugs?
2. Are A7 spark plugs for standard engines normally a 13/16 inch socket?
Any advice would be well appreciated.
Joined: Mar 2015 Posts: 5,443 Threads: 231
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Location: Scotchland
D21s are a hotter plug.
I have no experience of Accuspark plugs. In my experience D16 and D21 plugs work well in Sevens, D21 particularly so.
Joined: Jan 2019 Posts: 1,567 Threads: 20
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Location: Bala North Wales
Car type: 1933 RP Standard Saloon
I have D21s in my car following an earlier recommendation from Ruairidh. They have now done 5K miles and the car still starts and runs as well as it did when I first put them in.
Joined: Jun 2019 Posts: 15 Threads: 2
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Location: NZ
Car type: 1933 Austin 10/4
Old Dave, I use Accuspark AA77C on my 1933 Austin 10. However being three electrode design there is no way to set a gap. I have always worried about this as the gap essentially sets the dwell angle.
The car runs okay and I can’t detect any loss of power versus the NGK AB-6. Maybe Austin didn’t consider DA back in the day. Reason for the change was I got two batches of dud AB-6,s…. I think I got some Chinese knock offs although the supplier denied it.
I also run AA77C in my side valve Ariel VB600 and this bike runs okay as well.
I am considering using a plug adapter to take the plug hole down to 14mm. Not too expensive and plenty of plug choice at this size.
Before I used on the A10 I took the head off , fitted a AA77C to make sure the electrode didn’t project too far.
I can’t find the specs on the Accuspark web site now, but I recall the projected length was 1/2 inch which is close to AB-6 at 7/16 inch
Cheers
Gary
Auckland
Joined: Aug 2022 Posts: 149 Threads: 27
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Location: Cheshire
Car type: Austin 7 RN - 1932
Thanks Gary - that is very useful info. Plug gap was something I had not considered. It is likely I will fit them and see what difference I detect, if any.
I have messaged the company for clarification. As you say there is not much info to be had with regard to Austins on their website but the eBay listing clearly says for A7 and A10 A12 A16 and A20.
Thanks again for your experience of the AA77C
Joined: Aug 2017 Posts: 612 Threads: 19
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Location: Hampshire UK
Hi
It's the points gap that sets the dwell angle, not the plug gap.
Joined: Apr 2018 Posts: 507 Threads: 129
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Location: Staffordshire
Car type: Ruby mk 2
What’s the best source for D21’s
Joined: Jan 2019 Posts: 1,567 Threads: 20
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Location: Bala North Wales
Car type: 1933 RP Standard Saloon
I got mine from the Green Sparkplug Company,
Joined: Aug 2017 Posts: 1,641 Threads: 93
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Location: Monmouthshire
Note that the list of alternatives is dated 2015. Mr Green of Middlewich has become one of the trustworthy suppliers who now do a sharp intake of breath when “NGK” alleged plugs are mentioned. Quite how one brand gets into such trouble I do not know. So I add my voice to all the others, just avoid them.
