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

http://www.mazdatrix.com/pictures/tools/spark1.jpg 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.)

http://www.mazdatrix.com/pictures/tools/spark2.jpg The small diameter spark plug socket fits around the plug, and inside the ridge

http://www.mazdatrix.com/pictures/tools/spark.jpg 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 (http://www.mazdarotaryclub.com/forums/showthread.php?threadid=264&referrerid=1)

[MikeLMR]

Originally posted by gbutcher
Hi Mike - do you mean fan shrouds? from the radiator?

I mean the shoulder bit round the plug ... on the rotor housing

[Glenn Butcher]

Ah right!

Not sure really, do you know if you have the original engine in the car? I think the US models may have been different?

Be interesting to see what type of plugs the Factory Workshop Manual recommend? if they are the long type then you know that car in that country had "X" (long or short) plugs.

From memory the RX-7 Series 4 and 5 turbo/non turbo engines have the shoulder around the plug hole (they are the engines where we use to grind the shoulder off so we could run the NGK B8EGV's - Leading, B10EGV's - Trailing).

[MikeLMR]

My mate on the parts counter at Mazda looked up the plugs for my car in the parts book and they came out as NGK BR8ET's (like in the photo) which are the short ones. So I presume UK rx7's didn't have the shoulders on the 84-85 engines ?

Maybe its because we retained the old style emmissions systems ?

[mmilner]

Originally posted by Phranque
Silly me! I bought (for over £40) a set of NGK BR8ET plugs for the 12a in my Series 1.

Frank

Frank, Halfords have ripped you off. I recently bought 4 BR8ET's for my car from a mazda main dealer and they were £24.88 for the set!

With regards to your shroud/shoulder problem, my 1979 RX7's 'new' engine had those and that is why I had to use 'special' plugs, whereas the original didn't have that 'feature'. The replacement engine came with the shrouds/shoulders and BR7EQ plugs which is why I (as I have posted before) still have a box of 6 brand new ones which would probably have fitted your car going for £10 + p+p... (Too late to help you, it seems.) I will try and attach a pic of one below.

Martin.

[Glenn Butcher]

Hi Mike,

I knew I had this laying around, may explain a few things on the plugs? but I think Mazda would really have the answer.

http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf

Example:
BUR-9EQ - In the "BUR" model name of the spark plug. the "U"
stands for Semi-Surface Discharge. No need to gap Semi-Surfaced spark plugs.

[mmilner]

Originally posted by gbutcher
Hi Mike,

I knew I had this laying around, may explain a few things on the plugs? but I think Mazda would really have the answer.



Thanks for that Glenn! Confirms what I thought, that my BR7EQ's are virtually (if not) the same as BUR7EQ's and BUR7EQP's. (The P stands for a platinum electrode.)

Martin.

[Phranque]

Hi Glenn,
Thanks for the spark plug Q&A. I've just skimmed through it as yet and can see now why there's a difference between the leading and trailing plugs. I didn't realise there was so much to the business of plugs.

Yes Martin, I think you are right about Halfords, that's why I didn't even enquire when it came to trying for the SD plugs. Heaven knows what they would have charged.

Your BR7EQs will quite clearly fit my engine - do you want to do a straight swap for the set of four BR8ETs which I have? I'm sure they are better than my hanging on to plugs which don't fit. The BR8ETs are brand new apart from one having been run for about 60 seconds just to see if the engine would function with a finger-tight plug.
Frank

[mmilner]

Originally posted by Phranque

Your BR7EQs will quite clearly fit my engine - do you want to do a straight swap for the set of four BR8ETs which I have? I'm sure they are better than my hanging on to plugs which don't fit. The BR8ETs are brand new apart from one having been run for about 60 seconds just to see if the engine would function with a finger-tight plug.
Frank

A swap sounds good Frank. It'll save me buying the next set in a few months time. :)
You know where to send 'em to...

Cheers,
Martin.

[Phranque]

Martin,
That's fine! I've gone and deleted the email with your address - can you send it to me again please, or if you are going down to Brooklands we could meet there. I'm about 90% OK to go down there, it finally depends upon how my wife is at weekend.
Frank
frank_gw3cnm@hotmail.com



GLENN - if you're around, thanks for the new membership card. Very smart!

[Phranque]

Plugs arrived from Mazda (below) and backup of similar from Martin soon. All is now OK
Frank

[mmilner]

Out of interest, how many earth electrodes have they got Frank? (The plug name doesn't seem to follow any of the standards on the sheet Glenn posted....)

Martin.

[Phranque]

Hi Martin,
I've scrubbed the end of this plug up with emery cloth (shock - horror ! ) just for the photo. It couldn't be simpler really, heaven knows where they get the price from.
Frank

[MikeLMR]

I think the price comes from the number sold , they probably sell millions of times more Boinger plugs than the ones specially devised for the rotary.

Plus I think modern spark plugs are expensive anyway , regardless of what engine type

[Phranque]

I'm sure you're right, Mike.

Actually, although I was a little alarmed at the price I was also rather pleased to note that within a couple of days I was able to get an unusual spare part from Mazda. That's quite reassuring.

I'm now wondering whether to save up for a complete exhaust sytem as a spare. In the end it's bound to go and I'm sure the price has risen since I last enquired in about 1989 (£2200). Unless someone was pulling my leg in '89 ??? I might wander over to my friendly local dealer (60 miles) to see what he has to say. I don't want to have to fit a non-standard part when the chickens come home to roost.

It's looking dull here, Mike. I bet those piston engine types have been praying for rain.

[MikeLMR]

its rather nice in Lincoln today ... walked home from work without a coat on

[mmilner]

Originally posted by MikeLMR
I think the price comes from the number sold , they probably sell millions of times more Boinger plugs than the ones specially devised for the rotary.

There's no getting away from the fact, however, that Halfords charged almost double what Mazda did for the same plugs.:(

[mmilner]

Originally posted by Phranque
Hi Martin,
I've scrubbed the end of this plug up with emery cloth (shock - horror ! ) just for the photo. It couldn't be simpler really, heaven knows where they get the price from.
Frank

That's a wierd looking plug Frank! None of my RX's have had that type of 'earth electrode'. Anyone else seen them before?

[MikeLMR]

i've seen some like that in a lawn mower :D ... as for Halfords ! I think the 100% markup is the same on all there parts