Plugs for 12a ......HELP !!!!!!!

[Phranque]

Silly me! I bought (for over £40) a set of NGK BR8ET plugs for the 12a in my Series 1 only to find that they won\'t fit because of a casting shoulder round the hole where they go. The plugs fitted at present are NGK SD10A with a letter "T" below  and SD11A with a letter "L" below (see photo). One goes in the top position and one in the bottom position of each rotor.

These, I understand, are \'hot\' plugs and that\'s just fine for me because I won\'t be doing anything above Mach 0.0933 in the car.

So....
(1) Am I OK to order a set of SD10A/SD11A because some websites frown even on those and go on about BR8EQ-14 but without saying if they\'ll fit an engine with a casting shoulder like mine has.

(2) Anyone want to buy a set of BR8ET plugs, brand new. Any offers considered, even silly ones! Time wasters welcome, I\'ll listen to anything!

I don\'t want to have to push this thing all the 214 miles to Brooklands!

Frank

[MikeLMR]

I\'ve got BR8ET\'s in mine

[Phranque]

Mmmmmmmmm! That\'s strange, Mike. I wonder if this 6-ported 12a was perhaps different in ways other than porting?
Photo below (just a quick happy-snap) should show what happens when I try to fit BR8ETs !

[MikeLMR]

looks like the 12a 6PI\'s have different rotor housings

thats a shame  are the other plugs easy to get hold of ?

[Phranque]

I\'m not sure yet, Mike. I\'ll do the rounds on Monday and check on the net to see what\'s available.

Fingers crossed !

[Glenn Butcher]

Originally posted by Phranque
Mmmmmmmmm! That\'s strange, Mike. I wonder if this 6-ported 12a was perhaps different in ways other than porting?
Photo below (just a quick happy-snap) should show what happens when I try to fit BR8ETs !

Hi Frank,

How are you?

What we use to do was grind out the plug hole surround, with a made up tool.  We would screw in a broken off plug with screwdriver (make a slot in the broken off plug) then get a large round head (tapered) cutting tool in a drill, then remove the outer surround.

It was handy then, as we could run the different plug types (short and long).

Don\'t know if this helps - just for info. really.

[Phranque]

That\'s funny, I thought I\'d replied to this but the post ain\'t there, so.......

Hi Glenn,
I\'m probably not brave enough to do something like that, not yet anyway but thanks for the tip. Actually it\'s useful just to realise that it\'s not \'sacred ground\' and that things can be altered to accomodate new needs.
Really I want to try to keep it as original as possible so I\'ll hunt round for the right plugs first I think.
Me? Very well thanks. I found a shot of one of your cars on the web somewhere today. A silvery coloured one, forgotten what model. It looked very smart, I must say.
Frank

[MikeLMR]

What is the idea behind the shrouds around the plug holes then ? they don\'t seem to serve any purpose other than stopping people from fitting different plugs :confused:

[MikeLMR]

Spotted this today Frank

http://www.mazdatrix.com/toolmisc.htm

The \'81 and later rotor housings have an external ridge around the spark plug hole that prevents a conventional plug socket from being able to screw a short body plug all the way in. (The "normal" NGK plugs have a long body and do not require this tool.)

The small diameter spark plug socket fits around the plug, and inside the ridge

Small Diameter Spark Plug Socket is needed whenever short body spark plugs are used in 81 and later rotor housings.


HTH

Mike

[Glenn Butcher]

Hi Mike,

Good question, I don\'t know - just to be a pain for us

Maybe it was some agreement they had with NGK? or something to do with the Plug heat? - not sure.

Would be good to know though.

[MikeLMR]

the other strange thing is I have two 84 12a engines (one in my car and one in the spares car) and they both lack the Shrouds ? yet Mazdatrix claims all 81+ engines have them ? maybee that should be pre 81 engines ??

Mike

[Phranque]

OK Mike - that\'s an interesting socket.

I\'ve got the old plugs back in the engine now but from what I can recall there was little or no room for even the thinnest socket between the plug hex and the shoulder.

I hunted high and low for SD10A and 11a plugs and was coming up with blanks wherever I looked. After several hours yesterday I had almost given up. This morning I rang a Mazda dealer. He did a lot of head scratching but when I gave him part numbers - N338-18-110 and N339-18-110 he found them catalogued.

The good news is that a set of 2+2 = 4 should arrive on Wednesday, they are being flown in from Brussels. The bad news is the price ............ £39 for just one of each. £78 for the set, which is £28 more than I paid for my first whole car. He said that the plugs were used in an Australian model RX.

I\'m glad I ordered them B4 I had a plug failure though, at least they will be on the shelf (under armed guard).

Frank

[Phranque]

I forgot - apart from the shoulder \'puzzle\' which you are debating with Glenn, why is there a different plug for the top hole and the bottom hole? Just how critical can this plug business get to be? Apart from one having two pretty blue rings in the ceramic they look pretty much identical.

[Glenn Butcher]

Originally posted by MikeLMR
the other strange thing is I have two 84 12a engines (one in my car and one in the spares car) and they both lack the Shrouds ? yet Mazdatrix claims all 81+ engines have them ? maybee that should be pre 81 engines ??

Mike

Hi Mike - do you mean fan shrouds? from the radiator?

[Glenn Butcher]

Originally posted by Phranque
I forgot - apart from the shoulder \'puzzle\' which you are debating with Glenn, why is there a different plug for the top hole and the bottom hole? Just how critical can this plug business get to be? Apart from one having two pretty blue rings in the ceramic they look pretty much identical.

Hi Frank!

Have a read through this thread I put together a while ago, should explain things nicely :-)

Spark Plug Q & A\'s