AW: [xj] Spark Plugs

XJ
1

The Bosch 4 prong plugs are sad imititations of Surefire plugs. These were invented by an American whose son was killed in a WW2 fighter crash due to bad plugs. The evil spark plug industry sat on this idea till the patent expired & now a small company are making them. They’re kind of hard to describe. Instead of one prong, they’ve got 8 tabs. They’re self cleaning & never need gapping. They come with a lifetime guarentee and are fit & forget, a boon if like me, you own two V12’s. Down side ? Not cheap. They cost 4 pounds each (last time I looked). Ask the wife for a set for christmas.

Cheers,

Wilson.

-----Urspr�ngliche Nachricht-----Von: Graeme Adamson [mailto:claymore@iname.com]
Gesendet am: 15 November 1999 08:29
An: xj@jag-lovers.org
Betreff: Re: [xj] Spark Plugs

On Sun, 14 Nov 1999 20:22:07 -0800, Cannara cannara@attglobal.net said:

Paul, I personally think they’re a waste of time. Take one and connect it up
outside the engine and crank the engine over – if you see more that one arc
across the gaps, have another drink! Only one gap will break down at a time,
typically, so there’s no advantage as far as increased exposure to mixture.
In fact, the geometry of the plugs like these that I’ve seen actually reduce
exposure. Someone else may have had another experience, of course.

The way we had it explained by the Bosch chap was as follows:

With a conventional plug, you’ll get some carbon build-up on the casing of
the plug. Over time, as the gap widens, the spark may find it easier to
travel along the carbon instead of jumping the gap, causing misfires etc.

With four prongs (and the way they’re shaped and positioned), there are 8
possible ways the spark can happen. If carbon starts building up, it build
up near the inside edge of the prong, the gap there will close, the spark
will jump there, and the carbon will end up being burnt off, while still
sparking.

This is the Bosch +4 plugs. Pity they don’t fit XK 3.4, 3.8 or 4.2 engines
(or the V12 either, according to their guide).

Graeme

–

Graeme Adamson, claymore@iname.com
Jaguar XJ6 SII 1980: http://sherekhan.jumpautos.com
Committee Member: Jaguar Club of South Africa

Pournelle’s Law: If you don’t know what you’re doing,
deal with people who do.

2

The Splitfire plug is a waste of money, and most of the parts stores
around here have stopped selling them.
The design may have come from WW2, but nobody sat on it, not even the
“Evil spark plug industry”. Sorry Wilson, but you are wrong.
I remember back in the 50’s you could go to any Pep Boys store and buy
multi electrod spark plugs. They advertised them to even fire in oil.
So this plug has been around for many a year. Splitfire just did a BIG
advertising job on them and made so money from it.
A good and proper tuneup will do the same thing for your engine.
Chad Bolles Jaguar Performance, Inc 306 Valcour Rd Columbia SC 29212
803 798 3044 FAX 803 798 4512

Wilson Logon wrote:>

The Bosch 4 prong plugs are sad imititations of Surefire plugs. These were invented by an American whose son was killed in a WW2 fighter crash due to bad plugs. The evil spark plug industry sat on this idea till the patent expired & now a small company are making them. They’re kind of hard to describe. Instead of one prong, they’ve got 8 tabs. They’re self cleaning & never need gapping. They come with a lifetime guarentee and are fit & forget, a boon if like me, you own two V12’s. Down side ? Not cheap. They cost 4 pounds each (last time I looked). Ask the wife for a set for christmas.

Cheers,

    Wilson.
3

Dear Listers,

“Splitfire”, “Surefire”. Are we talking about the same plugs? I understand
about “indexing” plugs (gap towards inlet valve) and if that process does
increase power then multi-electrode plugs would be shielding the spark from
the mixture even more.
The way I see it is that multi-electrode plugs will not need re-gapping, so
“fit & forget”. What I am looking for is better combustion for better fuel
mileage, given the limits of the carb. V12 engine and my wallet :slight_smile:
I remember something, from years ago, like a fine mesh screen which fitted
between carb. and manifold. The idea was that it helped to atomise the
mixture, improving combustion. I suppose there must have been reasons why
it never caught on. Probably reduced air-flow too much. Anyone have any
experience?

Paul,
1974 Daimler 66Vdp.

Original Message-----From: owner-xj@jag-lovers.org [mailto:owner-xj@jag-lovers.org]On Behalf
Of Chad Bolles
Sent: 15 November 1999 16:16
To: Wilson Logon; xj-s@jag-lovers.org; xj@jag-lovers.org
Subject: Re: AW: [xj] Spark Plugs

The Splitfire plug is a waste of money, and most of the parts stores
around here have stopped selling them.
The design may have come from WW2, but nobody sat on it, not even the
“Evil spark plug industry”. Sorry Wilson, but you are wrong.
I remember back in the 50’s you could go to any Pep Boys store and buy
multi electrod spark plugs. They advertised them to even fire in oil.
So this plug has been around for many a year. Splitfire just did a BIG
advertising job on them and made so money from it.
A good and proper tuneup will do the same thing for your engine.
Chad Bolles Jaguar Performance, Inc 306 Valcour Rd Columbia SC 29212
803 798 3044 FAX 803 798 4512

Wilson Logon wrote:

The Bosch 4 prong plugs are sad imititations of Surefire plugs. These were
invented by an American whose son was killed in a WW2 fighter crash due to
bad plugs. The evil spark plug industry sat on this idea till the patent
expired & now a small company are making them. They’re kind of hard to
describe. Instead of one prong, they’ve got 8 tabs. They’re self cleaning &
never need gapping. They come with a lifetime guarentee and are fit &
forget, a boon if like me, you own two V12’s. Down side ? Not cheap. They
cost 4 pounds each (last time I looked). Ask the wife for a set for
christmas.

Cheers,

    Wilson.
4

It certainly will be easier to find a gap to arc across if there are 8, but
remember that WWII craft didn’t have electronic ignitions, which not only have
higher outputs, they shape the rise of the spark pulse to counteract some
effects of fouling. If an n-gap plug lets you avoid checking and gapping
every 20,000 or so miles and an electronic ignition lets you use regular plugs
for over 50,000, longer with cleaning and gapping, then…? My view is there
are much more important things to do with the money and Surefire, etc. can do
without mine. I get new plugs on our Hondas every time their engines are
rebuilt. {:o]

By the way, as most probably know, another way to reduce fouling and improve
ignition is to use “long-reach” (or “hotter”) standard plugs. These place the
gap further into the cylinder and expose more of the insulator (casing?) to
combustion, thus keeping it cleaner. Since we often use the color of deposits
to diagnose engine tuning, this makes that easier too. Of course the piston
must clear the plug! I’ve seen the difference on every car I’ve had, when it
started using oil, for instance, so I simply put these plugs in no matter what
the manufacturer supplied or the last mechanic put in.

Alex
79xj6

Wilson Logon wrote:>

The Bosch 4 prong plugs are sad imititations of Surefire plugs. These were invented by an American whose son was killed in a WW2 fighter crash due to bad plugs. The evil spark plug industry sat on this idea till the patent expired & now a small company are making them. They’re kind of hard to describe. Instead of one prong, they’ve got 8 tabs. They’re self cleaning & never need gapping. They come with a lifetime guarentee and are fit & forget, a boon if like me, you own two V12’s. Down side ? Not cheap. They cost 4 pounds each (last time I looked). Ask the wife for a set for christmas.

Cheers,

    Wilson.

-----Urspr�ngliche Nachricht-----
Von: Graeme Adamson [mailto:claymore@iname.com]
Gesendet am: 15 November 1999 08:29
An: xj@jag-lovers.org
Betreff: Re: [xj] Spark Plugs

On Sun, 14 Nov 1999 20:22:07 -0800, Cannara <@Cannara> said:

Paul, I personally think they’re a waste of time. Take one and connect it up
outside the engine and crank the engine over – if you see more that one arc
across the gaps, have another drink! Only one gap will break down at a time,
typically, so there’s no advantage as far as increased exposure to mixture.
In fact, the geometry of the plugs like these that I’ve seen actually reduce
exposure. Someone else may have had another experience, of course.

The way we had it explained by the Bosch chap was as follows:

With a conventional plug, you’ll get some carbon build-up on the casing of
the plug. Over time, as the gap widens, the spark may find it easier to
travel along the carbon instead of jumping the gap, causing misfires etc.

With four prongs (and the way they’re shaped and positioned), there are 8
possible ways the spark can happen. If carbon starts building up, it build
up near the inside edge of the prong, the gap there will close, the spark
will jump there, and the carbon will end up being burnt off, while still
sparking.

This is the Bosch +4 plugs. Pity they don’t fit XK 3.4, 3.8 or 4.2 engines
(or the V12 either, according to their guide).

Graeme

5

Paul, on the “mesh screen”, purse your lips and try to keep them pursed real
tight while you breath only through them – the hard work to do that is why it
won’t help to add such a thing to an existing intake design. Maybe a new one,
with far larger area could improve a fuel-air mix, but it’s these pumping
losses that would make an engine deliver less power, rather than more, if the
design weren’t done just right. Also why we should always drive in the
highest gear, with our right foot to the floor. {:o]

Alex
79xj6

Paul Clarkson wrote:

Dear Listers,
[clip]> I remember something, from years ago, like a fine mesh screen which fitted
between carb. and manifold. The idea was that it helped to atomise the
mixture, improving combustion. I suppose there must have been reasons why
it never caught on. Probably reduced air-flow too much. Anyone have any
experience?

Paul,
1974 Daimler 66Vdp.

6

Just to clarify,
“Long-reach” plugs have a longer threaded portion, so that they fit heads having the longer threaded area. The length of the exposed porcelin center insulator does differ in different heat ranges, but the plug doesn’t stick farther into the combustion chamber - that would be a nightmare of compatibiltiy calculation.
I agree that multiple gaps don’t seem to offer much for cars with electronic ignition.
Steve Russert> ----------

From: Cannara[SMTP:cannara@attglobal.net]
Reply To: cannara@attglobal.net
Sent: Monday, November 15, 1999 9:03 AM
Cc: ‘xj@jag-lovers.org’
Subject: Re: AW: [xj] Spark Plugs

It certainly will be easier to find a gap to arc across if there are 8, but
remember that WWII craft didn’t have electronic ignitions, which not only have
higher outputs, they shape the rise of the spark pulse to counteract some
effects of fouling. If an n-gap plug lets you avoid checking and gapping
every 20,000 or so miles and an electronic ignition lets you use regular plugs
for over 50,000, longer with cleaning and gapping, then…? My view is there
are much more important things to do with the money and Surefire, etc. can do
without mine. I get new plugs on our Hondas every time their engines are
rebuilt. {:o]

By the way, as most probably know, another way to reduce fouling and improve
ignition is to use “long-reach” (or “hotter”) standard plugs. These place the
gap further into the cylinder and expose more of the insulator (casing?) to
combustion, thus keeping it cleaner. Since we often use the color of deposits
to diagnose engine tuning, this makes that easier too. Of course the piston
must clear the plug! I’ve seen the difference on every car I’ve had, when it
started using oil, for instance, so I simply put these plugs in no matter what
the manufacturer supplied or the last mechanic put in.

Alex
79xj6

Wilson Logon wrote:

The Bosch 4 prong plugs are sad imititations of Surefire plugs. These were invented by an American whose son was killed in a WW2 fighter crash due to bad plugs. The evil spark plug industry sat on this idea till the patent expired & now a small company are making them. They’re kind of hard to describe. Instead of one prong, they’ve got 8 tabs. They’re self cleaning & never need gapping. They come with a lifetime guarentee and are fit & forget, a boon if like me, you own two V12’s. Down side ? Not cheap. They cost 4 pounds each (last time I looked). Ask the wife for a set for christmas.

Cheers,

    Wilson.

-----Urspr> �ngliche Nachricht-----
Von: Graeme Adamson [mailto:claymore@iname.com]
Gesendet am: 15 November 1999 08:29
An: xj@jag-lovers.org
Betreff: Re: [xj] Spark Plugs

On Sun, 14 Nov 1999 20:22:07 -0800, Cannara cannara@attglobal.net said:

Paul, I personally think they’re a waste of time. Take one and connect it up
outside the engine and crank the engine over – if you see more that one arc
across the gaps, have another drink! Only one gap will break down at a time,
typically, so there’s no advantage as far as increased exposure to mixture.
In fact, the geometry of the plugs like these that I’ve seen actually reduce
exposure. Someone else may have had another experience, of course.

The way we had it explained by the Bosch chap was as follows:

With a conventional plug, you’ll get some carbon build-up on the casing of
the plug. Over time, as the gap widens, the spark may find it easier to
travel along the carbon instead of jumping the gap, causing misfires etc.

With four prongs (and the way they’re shaped and positioned), there are 8
possible ways the spark can happen. If carbon starts building up, it build>
up near the inside edge of the prong, the gap there will close, the spark
will jump there, and the carbon will end up being burnt off, while still
sparking.

This is the Bosch +4 plugs. Pity they don’t fit XK 3.4, 3.8 or 4.2 engines
(or the V12 either, according to their guide).

Graeme

7

Steve, actually comparing two plugs for, say, our Honda, the one coming with
the car barely sticks into the combustion chamber, while the longer-reach,
replacement one has a longer insulator, same number of threads and sticks in
about 1/4" more. So, we just need to be careful to check the various plugs we
can pick up. There seems to be plenty of room in the Jag’s chamber, and I
have long-reach in there too.

Alex
79xj6

“Russert, Steven W” wrote:

Just to clarify,
“Long-reach” plugs have a longer threaded portion, so that they fit heads having the longer threaded area. The length of the exposed porcelin center insulator does differ in different heat ranges, but the plug doesn’t stick farther into the combustion chamber - that would be a nightmare of compatibiltiy calculation.
I agree that multiple gaps don’t seem to offer much for cars with electronic ignition.
Steve Russert
[clip]