About to fit a 123 ignition to my 120 (3.4 8:1)
Anyone have any practical suggestions for which curve to
use for general touring with 95-98 Ron fuel?
Also, what static time my to set?
Thanks.–
Bob XK120 dhc
Herts, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Thornsdale sent Sat 25 Jun 2016:
Bob . Cant help you with what you are requesting however I
would be very interested in what difference before and after
the installation of 123 Dist.–
The original message included these comments:
About to fit a 123 ignition to my 120 (3.4 8:1)
–
Morris Barnett XK 150 ots S 830933
Nanaimo BC., Canada
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Thornsdale sent Sat 25 Jun 2016:
Hi,
I have a 123 in my XK150 ( Original 3.8L 8:1 ).
Setting to 1 gave the best results ( default=0 )
Adjusted the green LED at 10 degrees before TDC.
Run’s great now for 6 Years.
Always starts direct, warm ( 1 sec ) or cold ( 5 sec )
Can’t compare it with standard ignition, as I never used it,
it was so worn that there was no profile left for lifting
the points, were al rounded.
regards,
Peter jan–
ruschp
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Thornsdale sent Sat 25 Jun 2016:
Bob I have used the 123 products for several years now with very
good results. I use a ‘‘Tune’’ model on my concours XK140 SE/MC and
was able to ‘‘fingerprint’’ the cam and timing. I also have a
standard 123 with presets and use position 3. Note the 123 units
now being sold may have static advance built in at 10 degrees.
Ascertain this first or you may over advance the engine.–
SSPro
Vancouver. BC, Canada
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from ruschp sent Sun 26 Jun 2016:
Are you using the entire 123 dis or just the 123 insert
into the original dis, replacing the points?
Thanks,
Bob–
'53 XK120 DHC
Memphis, TN, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from bobsxk120 sent Sun 26 Jun 2016:
This is the complete 123/JAG replacement distributor.–
The original message included these comments:
Are you using the entire 123 dis or just the 123 insert
into the original dis, replacing the points?
–
Bob XK120 dhc
Herts, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Thornsdale sent Sat 25 Jun 2016:
There is much, much written about this on the various
forums. However I would like to know what problem you are
trying to fix/improvement to make. On my 150 I went for as a
complete original set up as possible. so I had the
distributor rebuilt by the distributor doctor here in the
UK. I did however chicken out and have a pertronix pick up
model installed to save me maintaining points but apart from
that the car is standard and performs like a trouper. I even
do track days with it. With the 123 if you get it to work
reliably it will be fine, however I am not sure what spares
you will need to carry when you go on a long trip. Its an
expensive fix to a non existent problem in my opinion. I
wonder how they managed in the 1950’s to win all those races
:-)–
The original message included these comments:
About to fit a 123 ignition to my 120 (3.4 8:1)
–
Phil.D 3.8 etype, XKR,XK150 FHC, XK120 FH2.2 diesel Xtype
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Phil.Dobson sent Mon 27 Jun 2016:
Thanks Phil,
Let me say first that I am a newbie to this having only
bought my 120 18 months ago at the age of 67, so any and
all info is really helpful.
I guess this exercise is a bit like mission creep. I had
been experiencing misfiring and irregular tickover so I
thought I would try the Pertronics insert option. This had
the added appeal of not having to worry about inaccessible
points.
This failed to make any improvement and after much
googling and talking found that everyone who ever
installed a 123 never regretted it, so I am about to try
that option.
Incidentally, I have found that it is almost impossible to
work on the dizzy on my 120 without removing the top hose
forums. However I would like to know what problem you are
trying to fix/improvement to make. On my 150 I went for as a
–
Bob XK120 dhc
Herts, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Thornsdale sent Tue 28 Jun 2016:
Bob,
That the pertronics didn’t improve things would seem to
indicate that your distributor is no longer in order.
If you want to stay original, then send your dizzy to
distributordoctor.com Martin’s work is to the highest standards
(in my experience) and he will return your distributor to
exactly the same spec as it was the day it left the factory.
If you fit a 123 distributor you will have various advantages.
If you take a 123/tune, you can set the advance and vacuum
curves yourself, as well as a rev limiter, and store two sets
of maps, which you can select via an external switch (ie, you
can have a regular and a race map). I’ve installed a few 123s,
I particularly like the TUNE variant.
Not burning the points out if you leave the ignition on is a
benefit, as is not having to replace points.
Having a rev limiter is worth it, in my opinion. Even if you
trust yourself completely, the rev limiter still works if you
lend your car, or if a joyrider takes it for a spin.
The downside to the 123 is that if it fails internally you will
not be driving the car home. Keep your original Distributor in
the boot - this good juju is a guarantee that the 123 will work
forever (same goes with a spare fuel pump).
Andrew–
The original message included these comments:
This failed to make any improvement and after much
googling and talking found that everyone who ever
installed a 123 never regretted it, so I am about to try
that option.
–
1968 3.8S
Zurich, Switzerland
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
I think removing the distributor to work on it is easier than trying to
work on it in situ.
I have mine out now and I’ve decided to do a 123 replacement rather than
refresh it again as I did about 60,000 miles ago.
My passion for originality is slowly fading while my age-related
willingness to trust and pay a really good vintage British car
specialist (Bruce Jackson in Middlesex, VT) to do things I used to do
increases. I just paid him for 3.5 hours of labor to replace two of the
belts on the front of the Series 3 XJ6 - a nightmarish task that I have
done myself in the past and it probably took me about 14 hours to do
just one belt.
Bruce COn 6/27/2016 5:23 PM, Phil.Dobson wrote:
In reply to a message from Thornsdale sent Sat 25 Jun 2016:
There is much, much written about this on the various
forums. However I would like to know what problem you are
trying to fix/improvement to make. On my 150 I went for as a
complete original set up as possible. so I had the
distributor rebuilt by the distributor doctor here in the
UK. I did however chicken out and have a pertronix pick up
model installed to save me maintaining points but apart from
that the car is standard and performs like a trouper. I even
do track days with it. With the 123 if you get it to work
reliably it will be fine, however I am not sure what spares
you will need to carry when you go on a long trip. Its an
expensive fix to a non existent problem in my opinion. I
wonder how they managed in the 1950’s to win all those races
The original message included these comments:
About to fit a 123 ignition to my 120 (3.4 8:1)
–
Phil.D 3.8 etype, XKR,XK150 FHC, XK120 FH2.2 diesel Xtype
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Bruce Cunningham sent Tue 28 Jun 2016:
whew…lots of 123 folks…anyway…I maintain original Lucas
distributor, carry a points/condenser set spares but have
never used them in 20 years…I am now about to install a
rebuilt original Lucas and vac unit rebuilt with 40199e
curve. Guessing I may end up with 8-12 static instead of
spec 7 after road testing. I have in my garage replaced
points one time. Otherwise just a check and slight dress of
the contact points…along with fresh spark plugs now and
then. When something is a-’‘miss’’…I know where to look, how
to fix it. Original static timing was 5 deg BTDC on early
120s, then 7 deg (2.5 flywheel teeth) on later 120s, and 10
deg on most 140s. Mechanical advance changed with
distributor number changes as did point gap. (early .012,
later .016) and spark plug specification changed as did gap.
generally .022 to .025. Lucas Sports Coil allows a slightly
wider gap. (with increased voltage the spark size can be
greater thus possible improved rapid combustion). Mechanical
advance in the range of 24 deg to 30 deg will give total
(not including vacuum adv) in the range you want of 34 to
36, but WHEN all the mech comes in is important. If springs
are too stiff it will come in at very high rpm…not what you
want for normal driving. It should be all in around 2800 to
3100 rpm. Glenns Jaguar book has the mech adc specs and I
will go look it up in a while. The above is '‘general’ for
decent performance of most engines. Today’s gas burns at a
different rate than the 80 octane of the early 50s, which
also had less additives for cleaning (now injectors) and
anti knock. Unless you are racing and tuning for the day
there is no need to reset timing and curve every day or time
the temperature or humidity changes. So set to Spec or a
little more advance than spec. Jaguar then recommend in a
Service Bulletin to do final timing set by road test. You
climb a hill under load and advance timing til a slight
ping, then retard until the ping is gone. Do this with a
load in the car, on a warm day and you will be all set.
Engine will run cooler with correct timing. Yes replacing or
adjusting points can be done in situ if eyes are good, block
lower distrib ‘‘open’’ areas with bits of cloth or towell in
case of dropped small bits…yes, I pull the top hose out of
the way and hang upside down from the rafters.
Cheers
Nick–
Nick53XK120S
Spokane WA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Nick53XK120S sent Tue 28 Jun 2016:
Thanks to all for your advice. Fitting the 123 (basic, not
TUNE) tomorrow. I’ll post the results later.–
Bob XK120 dhc
Herts, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Nick53XK120S sent Tue 28 Jun 2016:
Nick,
Doesn’t hanging from the rafters make all the blood rush to your
head? I normally just stand beside the car.
Andrew–
The original message included these comments:
case of dropped small bits…yes, I pull the top hose out of
the way and hang upside down from the rafters.
–
1968 3.8S
Zurich, Switzerland
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Thornsdale sent Tue 28 Jun 2016:
As promised, a post-installation update.
Firstly, many folk have advised this but it’s worth
repeating, make sure you read and understand all the
instructions before you start.
Secondly, check all the external connections to the old
dizzy and the 123. My old dizzy (pretty sure it would
have been original in pattern if not 63 years old!) had a
screw on connector for the vacuum and screw on terminals
for the HT leads; the 123 has push fit for both so make
sure you have the necessary to make it all connect up. We
didn’t spot this until the 123 was in and set up, so a
good deal of temporary fixing was introduced to make it
work while I await delivery of push fit HT connectors.
Anyway, after removing the top hose, the old dizzy came
out easily with the clamp loosened (I wondered why the nut
was on the block side of the clamp bolt, but realised this
is in keeping with making everything about the dizzy as
inaccessible as possible.) Following the instructions it
was easy to set the advance curve (Twyford Moors
recommended 4 so that’s what we used) and relatively easy
to put the 123 in and set it up.
Then we were about to put the cap on and noticed the
different connectors. By splaying the copper and using
masking tape to build up the thickness we ended up with a
good enough fit for a test and timing check.
The car fired up first time and showed all timings exactly
as the advance curve in the instruction booklet. A short
test drive brought back the grin I got when I first drove
a 120 - exquisite.
Just waiting for the proper connectors now and a bit of
tidying up to do and we are all set for a long UK tour.
So far, after 6 miles on dodgy HT connectors, I am
delighted.
Thanks to all who have helped.–
Bob XK120 dhc
Herts, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Thornsdale sent Wed 29 Jun 2016:
Great result Bob.–
The original message included these comments:
Just waiting for the proper connectors now and a bit of
tidying up to do and we are all set for a long UK tour.
So far, after 6 miles on dodgy HT connectors, I am
delighted.
Thanks to all who have helped.
–
Phil.D 3.8 etype, XKR,XK150 FHC, XK120 FH2.2 diesel Xtype
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
Nick,
Just want to compliment you on your concise write up of the workings of
the Lucas vacuum/mechanical advanced distributor. Well done. Covers just
about everything and sums it all up nicely.
Regards,
John Brady
678462
Bedford, MA
In reply to a message from JagWaugh sent Tue 28 Jun 2016:
Doesn’t standing up all day make the blood all rush to your
feet? leaving your head empty? And of course we all know hat
happens to our brains blood supply, with resulting loss of
mind, when ‘‘aroused’’.
sorry for that image…
N.–
The original message included these comments:
Doesn’t hanging from the rafters make all the blood rush to your
head? I normally just stand beside the car.
–
Nick53XK120S
Spokane WA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
Is there a 123 distributor for the 1952 XK120?
Hi Bob very good mid night , Curve F will work 
Hello David, Twyford recommendation to Bob was for curve 4, which is 12 degrees at 500-1200 vacuum disconnected and 10 degrees BTDC, 21.2 degrees @ 2000 & 36 degrees @ 3300.
Can you explain to us how you think curve F ( the last curve on instructions ) would work at
25.4 @ 2000 & 42 degrees @ 3000.
Is this for a racing application with no vacuum or some other reason. Interested to know ??
