The colour of plugs when you take them out.

[Graham Honnor]

Hello Dave
As you are probably aware, the lower the number, the hotter the plug so I am in the same mind of thinking that the "4 "
may be a little too hot.
I was led to believe that the B6HS was the correct plug for our type of head but with mine, I found that they oiled up quite quickly. The change to a B5HS stopped that problem immediately for me but I will certainly try a BP5HS next time as Ian suggests as I have a lot of respect for his knowledge of these things.
I also always buy mine on Ebay and usually pay around the £6 mark with delivery included. (That's for 4 by the way).
Hope this helps a little.
Graham.

[Nick Turley]

Hello Dave
As you are probably aware, the lower the number, the hotter the plug so I am in the same mind of thinking that the "4 "
may be a little too hot.
I was led to believe that the B6HS was the correct plug for our type of head but with mine, I found that they oiled up quite quickly. The change to a B5HS stopped that problem immediately for me but I will certainly try a BP5HS next time as Ian suggests as I have a lot of respect for his knowledge of these things.
I also always buy mine on Ebay and usually pay around the £6 mark with delivery included.
Hope this helps a little.
Graham.

The BP5HS is definitely the one to go for for a normal Austin seven.
For those with 18mmm plugs I have found that the D21  is a good bet especially with mag cars.

[Graham Honnor]

Thanks for that Nick, it's good to know you'd recommend them as well.
Having never used a projected plug before, I presume the length is the same as a normal one is it, and there's no
chance of it protruding into the head too far?
Sorry if that's a daft question, and for hijacking your thread John.
Graham.

[DaveT]

Well, I've taken the plunge and placed an order from the Green Spark Plug Co. through eBay for 4 x NGK Copper Core Spark Plug BP5S, stock number BP5S-GS4 at a cost of £8.10 inc p&p.

It was also cheaper through eBay (timgreen880) than the company direct. 

Once I receive them and get round to fitting them I'll let you all know the results

Now I'm going to get a Beer and sit down and watch ENGLAND beat Croatia (fingers crossed)

[John Mason]

This might seem a stupid question but if you need a 22 MM spanner to tighten/ untighten your spark plugs does this mean they are 22 MM plugs.

John Mason

[Chris KC]

This might seem a stupid question but if you need a 22 MM spanner to tighten/ untighten your spark plugs does this mean they are 22 MM plugs.

John Mason

Stop me if I'm missing something, but plug 'size' is the size (nominal diameter) of the screw thread, not the 'across flats' nut size.
Just as a 6mm bolt is 10mm across flats, for example, and needs a 10mm spanner to undo it.

[John Mason]

Chris You are correct with bolt and studs. I was'nt sure about plugs. This will mean a plug that needs a 22 MM spanner will be an 18 MM plug.

John Mason

[Matt_Harnden]

I have been reading the feedback about different spark plugs with great interest. Does anyone have any experience of running different plugs in 'non standard' cylinder heads? My special is fitted with a Supaloy head. At the moment it has Champion L86C plugs. Would there be much benefit in fitting 'hotter' plugs such as the NGK B5HS or BP5HS?

Matt Harnden

[Steve Berg]

I have also followed this information on Spark plugs with interest. Are all the ones mention 14mm plugs?
I use 18mm plugs on my Nippy but I suppose the same rules apply. Mine are always sooty.
Just that I get the impression that the choice of 18mm plugs is rather limited. And more expensive, particularly out here in Switzerland.