Spark Plugs

[Ray White]

Hi

It's the points gap that sets the dwell angle, not the plug gap.

Absolutely.  The dwell angle (or period through which the points remain closed) is fixed by the points adjustment.  The sparking plug gap has no influence on this; although the size of the gap will have an effect on performance.  Too big and a mis fire will occur; too small and the spark will be weak.  

What you are aiming for is the "Goldilocks" setting.

[nrzam]

Some discussion here -

https://www.rhocar.org/index.php?/forums...ark-plugs/

[Tiger]

Thanks Jeff
Ordered the NGK alternative

[Old Dave]

Thanks for all the insights into spark plugs for the A7.

I have messaged Accuspark through eBay as they will not address any eBay purchases direct - fair enough I suppose. Will wait and see. They look well made and are keenly priced.

I have messaged them direct to ask which plug should be used. If you look in Accuspark's electronic ignition conversions for the A7 they suggest a different plug namely   AF7C which appears to be for the Ford Pinto engine. !!!!!!

On the subject of what size plug socket is needed. I am surprised that this is not part of the listing info. As I said in the OP the Accuspark AA77C needs a 7/8 inch socket and according to my digital calipers the plugs measure 21.9mm across so a 21mm plug spanner will not do. The only new 7/8 inch plug socket I have spotted so far is £56 on Amazon. Perhaps this size is more prevalent in the USA?

Who would have thought spark plugs could be this complicated?   Or is just me?

[Tiger]

Dave I use a 22mm ring spanner after experiencing similar spanner fits.
This is a really good fit on the plug.

[Steve Jones]

Today I've fitted a new set of NGK AB6 plugs to my Ulster as part of getting it prepared for the Manx Classic Hillclimbs at the end of the month. Have used AB6s (and A6s before them) for many years without problems and always buy from Tim Green. These were from their latest delivery from NGK's UK importer received by them on Friday and received by me yesterday. The main problem with NGK plugs is the many fakes that are around. You can't, really, blame NGK for that but if you buy on price from some spurious supplier on the internet rather than a trusted source that has been around for years you should, perhaps, blame yourself.

Steve

[John Cornforth]

Hi

I believe Ford Pinto plugs have an 18 mm thread but with a taper seat. Not much good for an A7 with a conventional flat seat.

[Old Dave]

Thanks for that Tiger. I know I have up to 20mm, but will look through my big bag of spanners. I might have a 7/8 inch ring if not. AF spanner’s are in another big bag somewhere.

You are of course correct Steve Jones.

I was keen to give the Accusparks a go and will fit them when I am assured that the slight extra reach will not cause a problem.. I was surprised that the various makes have different hex sizes though I think the Champions and Accuspark are the same??

[Jeff Taylor]

According to the Green Spark Plug website - Champion D21 take a 22.2mm (7/8") plug socket whereas the NGK AB2 and AB6 take a 20.8mm (13/16") socket.

They can also supply a Melco (British Made) Spark Plug Box Spanner (Hex 1" x 7/8" A/F) for £11 - part no. SPT53.

   

[Old Dave]

Hi

I believe Ford Pinto plugs have an 18 mm thread but with a taper seat.  Not much good for an A7 with a conventional flat seat.

Interesting John - it will be even more interesting to see what Accuspark have to say when they get back to me!!!!

---

According to the Green Spark Plug website - Champion D21 take a 22.2mm (7/8") plug socket whereas the NGK AB2 and AB6 take a 20.8mm (13/16") socket.

They can also supply a Melco (British Made) Spark Plug Box Spanner (Hex 1" x 7/8" A/F) for £11 - part no. SPT53.

Thanks Jeff for the info - that pretty much summarises what I have measured. The Accuspark is the same as the D21 and D16.

I might have to go with a box spanner as shown. I had hoped to use a protected socket, but I guess I shouldn't be such a snowflake. May be the 22mm / 7/8 inch ring as Tiger suggested.

I will post what Accuspark have to say when I receive it. It is the slight extra reach of the AA77C 's that I want clarity about.