[Mg-mmm] MG PA spark plugs

[Lawrie Alexander]

Hiro,

Thank you for telling us that you tried three different styles of plug, each 
of which took the spark further out of the combustion chamber. The results 
of your test were exactly opposite to what I would have expected!

That is why I raised the question in the first place, to see if anyone had 
any experience with the longer, projected tip plugs. Obviously, there is 
something at work here which I don't understand. However, I like your 
comment that plugs are cheap and that experimentation is part of the fun of 
owning old MGs. Once the engine is back in the car, I shall try a set of 
BP6ES to see if they make a noticeable difference from the B6HS.

I shall report my findings in due course. For now, thanks to all who offered 
comments on this subject.

Lawrie
----- Original Message ----- 
From: "Hiro Nishio" <hiro at octagongarage.com>
To: <pthelander at earthlink.net>; <TATERRY at aol.com>; <lawrie at britcars.com>; 
<mg-mmm at autox.team.net>
Sent: Tuesday, October 27, 2009 9:14 PM
Subject: RE: [Mg-mmm] MG PA spark plugs


> Lawrie, Terry, Pete, and all,
>
> First of all, there are usually two reach lengths available, longer one is
> 3/4"(19mm) and shorter
> one is 1/2"(12.7mm). In case of NGK, "BP" means longer one, and "B" means
> shorter one.
> 3/8" (9.5mm) is hardly used in my case.
> And there are two kind of tips, extended one (ES) and normal (HS).
> Hence BP6ES has 3/4"(19mm) reach and extended nose. B6HS has 1/2"(12.7mm)
> reach and normal tip.
>
> Theoretically I think the long reach + extended nose plug would ignite 
> well
> inside the combustion chamber,
> but after trying many kinds of plugs including iridium to M/J/P/F/K/L/Ns,
> the actual result was vary,
> some car was good with BP6ES, but some was good with B6HS.
>
> Recently I rebuilt an F Magna engine (it had 14mm thread instead of 
> original
> 18mm - someone in the past
> modified) and I thought BP+ES should be good by exactly the same thought 
> as
> Lawrie.
> Then fitted BP6ES first, not satisfied. Then changed to BP6HS, which I
> usually use for any normal MMMs,
> better but not perfect, then finally B6HS, very good. No misfire occurred 
> at
> all finally.
>
> Lawrie, spark plugs are cheap, so try many and find the best one - it is 
> one
> of the fun given to us
> to play with old MGs.
>
> But do not use iridium plugs! That's expensive but no good for MMMs, 
> unless
> rather lean mixture setting.
>
> Good luck,
> Hiro
>
> -----Original Message-----
> From: mg-mmm-bounces at autox.team.net [mailto:mg-mmm-bounces at autox.team.net]
> On Behalf Of Pete Thelander
> Sent: Wednesday, October 28, 2009 9:11 AM
> To: TATERRY at aol.com; lawrie at britcars.com; mg-mmm at autox.team.net
> Subject: Re: [Mg-mmm] MG PA spark plugs
>
> Lawrie, Terry et al,
>
> I have been using the NGK BP6HS for the past ten years in the NE.  The 
> 1/2"
> reach plugs are a bit short, but that is why I run the extended tips.  So
> far as Terry using 5s and my using 6 or 7s,  The compression ratio is up 
> to
> the original spec at 9.8:1.  I don't think Terry is near that high, so the
> 5s might be more appropriate for his car.
>
> Pete
> pthelander at earthlink.net
>
>
>
>> [Original Message]
>> From: <TATERRY at aol.com>
>> To: <lawrie at britcars.com>; <mg-mmm at autox.team.net>
>> Date: 10/27/2009 4:23:00 PM
>> Subject: Re: [Mg-mmm] MG PA spark plugs
>>
>> Lawrie, I am using NGK BP5HS plugs in the NA....seem to work well but not
>> so much time or mileage yet....these are 1/2" reach with an extended
>> nose....recommended by Bob Bazzica for use in all my cars, TA, TF, Arnolt
> and NA.....
>> What are others using?
>> Terry
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