[xk] Ignition Timing

One more question, with the timing mark on the flywheel two
teeth before the timing mark on the flywheel casing, should
the rotor be pointing forward, ie at the radiator?

Thanks,

Paul–
PDM#
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In reply to a message from PDM# sent Fri 14 Sep 2012:

The best way to check that is to roll the engine over until
the #1 cylinder is at top dead center, and then look at
where the rotor is pointing. If it is not pointing anywhere
in the direction of the #1 plug wire contact on the inside
of the distributor cap, then it is highly likely that the
mechanic did in fact remove the distributor and moved it out
of position. If so, you will need to pull the distributor
assembly up and out of the block and reinsert it so the
drive cog teeth get aligned with the drive gear, so the
rotor ends up pointing at #1 contact point inside the
distributor cap. It may take a few iterations to get it set
correct so be patient. A few degrees of advance or retard
adjustment can be made with the micrometer wheel on the side
of the distributor, but not many.–
Oppie
Wesley Chapel, Florida, United States
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In reply to a message from Oppie1 sent Fri 14 Sep 2012:

I would think it would be difficult to do the conversion with the
distributor still attached to the engine, but it could probably be
done. But even so, the drive dog on the distrbutor shaft is offset
so that it only fits in one way, so it is impossible for the timing
to be ‘‘off a tooth’’ as would be possible for other vehicles.
Unless he also removed the plug wires, you have to be able to bring
it back in time by rotating the distributor housing.–
The original message included these comments:

mechanic did in fact remove the distributor and moved it out
of position. If so, you will need to pull the distributor
assembly up and out of the block and reinsert it so the
drive cog teeth get aligned with the drive gear, so the


Mike Spoelker
Louisville,Kentucky, United States
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In reply to a message from PDM# sent Fri 14 Sep 2012:

With #1 cylinder at TDC on the compression stroke (both valves
closed) the rotor should be pointing towards whichever plug wire
terminal that feeds the #1 spark plug.–
The original message included these comments:

teeth before the timing mark on the flywheel casing, should
the rotor be pointing forward, ie at the radiator?
Thanks,


Mike Spoelker
Louisville,Kentucky, United States
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The Rotor should be pointed towards the #6 Cylinder Lug inside
the distributor cap (as per Factory Service Manual, pg B.52).
Charles #677556.
http://xktx.org.----- Original Message -----
From: “PDM#”

One more question, with the timing mark on the flywheel two
teeth before the timing mark on the flywheel casing, should
the rotor be pointing forward, ie at the radiator?

Thanks,

Paul

While Mike S’s statement is true… as with ANY cylinder at TDC, the
rotor should point to THAT cylinder’s lug within the distributor cap!!
It should also be noted for clarity that the XK Engine “times” on the
#6 Cylinder…
Charles #677556.
http://xktx.org.----- Original Message -----
From: “Mike S”

In reply to a message from PDM# sent Fri 14 Sep 2012:

With #1 cylinder at TDC on the compression stroke (both valves
closed) the rotor should be pointing towards whichever plug wire
terminal that feeds the #1 spark plug.

The original message included these comments:

teeth before the timing mark on the flywheel casing, should
the rotor be pointing forward, ie at the radiator?
Thanks,

Mike Spoelker
Louisville,Kentucky, United States

In reply to a message from cb@XKTX.Org sent Fri 14 Sep 2012:

To add a little to Mike’s comment, while the distributor
driving dog (i.e. square peg end) is offset, it is only
offset a little bit, and it is possible for an inexperienced
person to put it in 180 degrees off and it still might seem
to sort of fit, even though the shaft would not be fully
inserted. The inexperienced person would then discover that
the car won’t start, and might either rotate the distributor
body a lot or try shifting the wires around until it starts.
Also if the rebuilder took the whole thing apart, the upper
centrifugal advance shaft can go in two ways and thus could
be 180 degrees off.
Just some other things to look for.–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
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In reply to a message from Rob Reilly sent Fri 14 Sep 2012:

The more I dig into this, the more I find wrong. Looks like
when he took the distributor cap off and moved it aside, he
pulled three spark plug wires out of the cap, separating the
wires from the copper caps, now I’m wondering if the spark
plug wires are routed properly. Can anyone tell me the
proper routing of spark plug wires from the cap to the plugs?

I think the distributor is off 180 degrees but I want to
make sure everything else is right before I rotate the
distributor.

So much fun to work on the conveniently located distributor!
I think I have invented at least 5 new curse words.

Thanks,

Paul–
The original message included these comments:

To add a little to Mike’s comment, while the distributor
driving dog (i.e. square peg end) is offset, it is only
offset a little bit, and it is possible for an inexperienced
person to put it in 180 degrees off and it still might seem
to sort of fit, even though the shaft would not be fully
inserted. The inexperienced person would then discover that
the car won’t start, and might either rotate the distributor
body a lot or try shifting the wires around until it starts.
Also if the rebuilder took the whole thing apart, the upper
centrifugal advance shaft can go in two ways and thus could
be 180 degrees off.


PDM#
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In reply to a message from PDM# sent Fri 14 Sep 2012:

Does it start at all, or will it not start?

In all matters here, when Charles speaks, the wise listen… As he
correctly notes, #1 is at the rear, #6 at the front, and at any
given time the rotor should point toward the terminal of the
cylinder that is at TDC on compression.

Firing order is 1-5-3-6-2-4–
The original message included these comments:

So much fun to work on the conveniently located distributor!


Mike Spoelker
Louisville,Kentucky, United States
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Paul;
Roughly speaking, the plug wires run from Dist Cap, all
but straight up (IIRC, on a 120, the wires pass behind of the
upper radiator hose elbow on the intake, adjust accordingly
for 140), then up over the Intake Cam cover, into the “valley”
and, if so fitted, into the H.T. Conduit that attaches to the head.
Simple.
Also, as Rob R noted, the dist CAN be fitted 180 out (by
some ham-fisted yea-whoo)… The dogs would have to be
forced together, the dist will rotate, but the dist body will
NOT sit right against the block… If you suspect it is 180 out,
Check NOW before you do anything else (like try to start the
engine!)
You don’t “rotate” the dist to align properly, you remove
the entire dist (loosen the clamp-bolt at the join of dist body
and block), lift-out the dist. (completely removing it!) Check
the shaft “drive dog” for burrs, banged-over metal, etc.
(repair as required), “eye-ball” the “dogs” to determine the
position the dist shaft needs to be, rotate the distributor shaft
as required, refit the dist into the block… aligned properly,
the “dogs” will mesh together without issue and the dist body
will sit flush to the block… The dist will not cant or rock,
once the clamp bolt is tightened. (you only need to “tighten”
the bolt, NOT kill it!! Overtightening can and will cause
damage to the distributor body, not to mention the ring
clamp, itself!)
Charles #677556.
http://xktx.org.----- Original Message -----
From: “PDM#”

The more I dig into this, the more I find wrong. Looks like
when he took the distributor cap off and moved it aside, he
pulled three spark plug wires out of the cap, separating the
wires from the copper caps, now I’m wondering if the spark
plug wires are routed properly. Can anyone tell me the
proper routing of spark plug wires from the cap to the plugs?

I think the distributor is off 180 degrees but I want to
make sure everything else is right before I rotate the
distributor.

So much fun to work on the conveniently located distributor!
I think I have invented at least 5 new curse words.

Thanks,

Paul

In reply to a message from cb@XKTX.Org sent Fri 14 Sep 2012:

One more point about ignition timing with a Pertronix. I
had always set my timing as others have described above, and
then did the final adjustment using the micrometer and a
small 12V light clipped on across the points- so called
static timing. One or two clicks of the micrometer either
way would turn the light off or on as the points opened and
closed allowing a pretty accurate setting.

But after fitting the Pertronix I found that this method
didn’t work very well. The null point was in a range of
about 20 clicks of the micrometer- don’t know why this
should be so unless it is that the Hall effect sensor
doesn’t give a very sharp signal when the rotor’s turning at
such a low speed.

So I set the static timing near the middle of the range and
then checked it using a strobe-type timing light with the
engine running at idle. This showed that the timing was
right on and nice and stable. But I always finish up by
driving the car and adjusting to get good performance with
no ping.

Bruce Wright
#674699
Bruce Wright XK120 OTS #674699
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Hi Bruce,

Good point, and you’re right, what you have observed is a characteristic of
the Hall effect sensor. With points, there is a distributor position where
they are closed and just a bit later they are open. The transition occurs
at a very specific point. A Hall effect sensor has built-in hysteresis,
which makes it work like a toggle switch. With a toggle switch there is no
sharp transition point but rather a no-mans-land in the middle where nothing
happens. For example, when you turn a light switch on you need to move it
about 3/4 of the way to the top before the light goes on. To turn the light
off you need to move it 3/4 of the way to the bottom. There is no spot in
the middle where all the action takes place. With your Pertronix you can
time it statically if you adjust the micrometer until the light goes ON and
then leave it there without trying to go back and make the light go off
again. That said, there’s also no problem with using a timing light as long
as you are idling slowly enough that the centrifugal advance doesn’t start
to come into play.

Mike Eck
New Jersey, USA
www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2>

One more point about ignition timing with a Pertronix. I
had always set my timing as others have described above, and
then did the final adjustment using the micrometer and a
small 12V light clipped on across the points- so called
static timing. One or two clicks of the micrometer either
way would turn the light off or on as the points opened and
closed allowing a pretty accurate setting.

But after fitting the Pertronix I found that this method
didn’t work very well. The null point was in a range of
about 20 clicks of the micrometer- don’t know why this
should be so unless it is that the Hall effect sensor
doesn’t give a very sharp signal when the rotor’s turning at
such a low speed.

So I set the static timing near the middle of the range and
then checked it using a strobe-type timing light with the
engine running at idle. This showed that the timing was
right on and nice and stable. But I always finish up by
driving the car and adjusting to get good performance with
no ping.

Bruce Wright
#674699

In reply to a message from Bruce Wright sent Sat 15 Sep 2012:

Good news, appears the distributor is on correctly, rotor
aligned with property cylinder, 3 of the spark plug wires
into the distributor cap had separated from the copper
washers, guessing that is why car was running so poorly.
The list has anticipated my next question about Petronix and
the micrometer, I followed the same process Bruce had
described when I was running points and had the same issue
seemed the micrometer adjustments were not having the same
effect as when I was running points. I will set the
micrometer in the middle of the range and adjust from there.

Thanks everyone!

Paul–
The original message included these comments:

One more point about ignition timing with a Pertronix. I
had always set my timing as others have described above, and
then did the final adjustment using the micrometer and a
small 12V light clipped on across the points- so called
static timing. One or two clicks of the micrometer either
way would turn the light off or on as the points opened and
closed allowing a pretty accurate setting.
But after fitting the Pertronix I found that this method
didn’t work very well. The null point was in a range of
about 20 clicks of the micrometer- don’t know why this
should be so unless it is that the Hall effect sensor


PDM#
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In reply to a message from PDM# sent Sat 15 Sep 2012:

Hi
I installed a new Petronix Flame Thrower Distributor to my XK 120,
the instructions state solid core ignition wires must not be used,
i had new copper wire leads on the old Distributor and had to
change to new modern silicone coted wires, the car runs well with
this setup, starts first time and runs strong. When I set the
timing I adjusted the Distributor manually to get even smooth
running with no pinking under load, seems to work well. Hope this
helps.
Regards
Michael S
XK120 ots
XK 140 fhc–
jagman
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In reply to a message from newrynuck sent Sat 15 Sep 2012:

I have solid copper spark plug wires, and mine has been
running fine for years with the Pertronix, and Flame Thrower
coil. I think the reason for the warning against solid core
wires is possible interference with the ECU. Since I don’t
have an ECU, I don’t have to worry. The only one that has to
worry, is that guy in the Corvette that pulls up next to me
and wants to race. I step on the gas and emit all kinds of
nasty interference to his ECU, and leave him in a cloud of
dust…Just kidding of course:-) I don’t have a radio, so I
have no clue as to what it would do to the reception.
Joel–
The original message included these comments:

I installed a new Petronix Flame Thrower Distributor to my XK 120,
the instructions state solid core ignition wires must not be used,
I had new copper wire leads on the old Distributor and had to
change to new modern silicone coted wires, the car runs well with


ex jag, '66 E-type S1 4.2, '56 XK140dhc, '97 XJ-6
Denison, TX, United States
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