my mind is baffled with…what is the relationship of the
flywheel TDC mark, with where #6 will be, relative to the
number of flywheel full 360 deg rotatons (mark at window) to
have #6 at TDC compression. Another way,…if #6 is at TDC
on compression…how many times does the flywheel mark rotate
and pass/come to window…to be back on TDC compression. Will
the flywheel mark be at TDC again when #6 is TDC on exhaust,
and…Another way…is it correct that each 120 deg of
rotation brings one of the six pistons to TDC compression,
and one to exhaust.
aaaaarrrggghhhh mind is now tangled.
Finally…is it correct that the engine (damper/flywheel)
should only be rotated in it’s normal operation direction
(counter-clock…from ‘‘drivers’’ view position) ) to get
flywheel mark to window…(maybe except small back and forth
to get exact once very close.)
Nick–
Nick53XK120S
Spokane WA, United States
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Nick;
The mark on the XK120’s Flywheel is “TDC” for #6 and
#1… It MAY or MAY NOT be “The Compression Stroke”
for #6… This YOU must determine by either looking at the
position of cam lobes and/or the distributor rotor.
So, the answer to your question is: "Twice! The number
of rotations of the Crankshaft/Flywheel MIGHT need to
rotate to bring the #6 Piston on Compression Stroke/Top
Dead Center- (SM Pg B.41)
If you assembling an engine, most of the “indicators” are
in full view… If, on the other-hand, you are “just checking
the timing”, then your rotor shows which cylinder is “firing”
(at TDC- zero degrees AFTER Compression Stroke/Before
Power Stroke. Timing is, of course, set to 5 degrees, approx.
two teeth, BEFORE Top Dead Center (BTDC)…(SM Pg B.52
“Distributor, To Remove and Refit”).
The mark on the Flywheel is, again, Top Dead Center ONLY!..
The easy way to determine Compression Stroke is simple…
just put your finger over the open spark plug hole… Even if
the engine is turned my hand, your finger will block enough
pressure that you will “feel” it escaping past the sides of
your finger…
Once TDC on the Compression Stroke is reached, the
Flywheel Mark is lined-up in the window, NOW you can
rotated the engine BACKWARDS to get the “Before TDC”
Firing Point aligned (two teeth BTDC), as necessary
Now, all that said, IF you are adjusting/timing your CAMS,
THIS is when you DO NOT want to rotate the Engine
BACKWARDS!! The Serrations in between the Cam Mount
Plate and the Cam Chain Sprocket are so fine, that reversing
the engine WILL throw your cam timing OFF by several
degrees… (Plate B.21 on Pg B.43 shows these details, Pg B.41
“Valve Timing” describes the “How To” of the operation!)…
THIS is when (how) one’s cam timing can get out-of-whack,
leading to a timing-induced over-heating condition, as
Geo C. mentioned a few days ago!!.
As far as bringing “each” pair of pistons to TDC, every
120 degrees, you would NEED to mount a good Degree
Wheel on the Crank, to be accurate… this would require
either pulling the radiator or the engine… The easiest way
is the “finger method” to determine TDC for each piston…
(I used a simple TDC indicator-- works on Hemi Heads)
To know when said piston is firing, look at the distributor
rotor, compare to the dist cap and where the plug wires go.
I do NOT know why you’d NEED to know TDC for the
other pistons… If you are adjusting your valves, just rotate
the engine until the Cam Lobe of the valve in question is
180* AWAY from the valve stem. Easy The “Simple”
method would be to just pull the head and set it on wood
blocks!)
You got all that?? Good, the test will be Sept 3rd ;-}
(SM Pg. B.63 “Engine Tuning”)
Charles #677556.
PS: You DO know my favorite Acronym, don’t you?? ;-}----- Original Message -----
From: “Nick53XK120S”
my mind is baffled with…what is the relationship of the
flywheel TDC mark, with where #6 will be, relative to the
number of flywheel full 360 deg rotatons (mark at window) to
have #6 at TDC compression. Another way,…if #6 is at TDC
on compression…how many times does the flywheel mark rotate
and pass/come to window…to be back on TDC compression. Will
the flywheel mark be at TDC again when #6 is TDC on exhaust,
and…Another way…is it correct that each 120 deg of
rotation brings one of the six pistons to TDC compression,
and one to exhaust.
aaaaarrrggghhhh mind is now tangled.
Finally…is it correct that the engine (damper/flywheel)
should only be rotated in it’s normal operation direction
(counter-clock…from ‘‘drivers’’ view position) ) to get
flywheel mark to window…(maybe except small back and forth
to get exact once very close.)Nick53XK120S
Spokane WA, United States
In reply to a message from cb@risebroadband.net sent Sat 27 Aug 2016:
thank you Charles…printing that and putting on my wall.
I will do some checking…I am just now verifying…or
not…set up done by DPO…and…it seems…so far…that when
TDC arrow on flywheel is at mark on bell housing
window…that both 1 and 6 are at BOTTOM !!! a soft plastic
tube thru plug hole shows bottom…when flywheel marks are
lined up…but car runs just fine and always has…so could
it be the entire set up from cams to distributor-plug wiring
are all set up in some very strange way…I will let you know
what I find…but car is running just fine. (I will check
where 2-3-4-5 are, it would seem that every 120 deg of
rotation a new piston, in the firing order comes up to TDC
on compression…and a new one on exhaust.) And I will look
thru oil fill for #6 exhaust cam to be pointing up on
compression/firing…and down on exhaust.
Om my car, the distributor rotor when at #6 distrib cap to
wire to #6 (front) plug…rotor is toward right front corner
of engine block…more or less.
Nick–
Nick53XK120S
Spokane WA, United States
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In reply to a message from Nick53XK120S sent Sat 27 Aug 2016:
So somebody put your flywheel on wrong, 180 degrees out from
where it should be. Or could it be the wrong flywheel?
It is a big job to fix it. You could do it in place by
pulling the trans out, but probably easier to have the
engine out.
As I recall the flywheel has 132 teeth. For now, you could
count 66 teeth from the arrow and put a mark of white paint
or something.–
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 Sun 28 Aug 2016:
I think Rob that what you suggest may be the case…a lot of
work was done by DPOs…so I will do some checking…plan is
all plugs out, dizzy cap off…and by rotating engine…note
where all the parts are…when…ie what piston is TDC, firing
and where is flywheel and dizzy rotor. I think I will mark
flywheel with a different ‘‘color’’ of nail polish, every 1/3
of rotation when a cyl is TDC on comp. fortunately modern
female fashion has lots of nail polish colors.
anyway…just now curious…since it runs well…however off
the flywheel may be makes no diff as long as it is set up to
that config…and that I know that for setting timing.
I will let U know results of my checks. and yes…correct
flywheel is 132 teeth, (i will check mine) and each tooth
thus very close to 2.73 degrees. Seems to me then that every
44 teeth a new cyl is at TDC on compression…as it takes two
flywheel revolutions to fire 6 cyls. (the dizzy rotor
rotates at half the crank/flywheel revs)…right?
Nick–
Nick53XK120S
Spokane WA, United States
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In reply to a message from Nick53XK120S sent Sun 28 Aug 2016:
Yes, two crank rotations for every dist rotation.
You can see the flywheel teeth better on the bottom if you
take off the cover plate. It may be easier to count 66 teeth
under there.
The flywheel has two dowel pins so it can only go on two
ways - 180 degrees apart.
I would leave the dist where it is, since you know it works
as is. The only thing wrong is the flywheel.
You asked about turning it backwards. If you were setting
cam timing you don’t want to turn it backwards because cam
timing would be affected by backlash in the timing chain.
But there is very little backlash in the distributor drive
gears so ignition timing would not be much affected by
turning the crank backwards.–
The original message included these comments:
44 teeth a new cyl is at TDC on compression…as it takes two
flywheel revolutions to fire 6 cyls. (the dizzy rotor
rotates at half the crank/flywheel revs)…right?
–
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 Sun 28 Aug 2016:
thanks…yes 66 to get half way round…and I will see where #
1 and 6 are then. Kinda reminds me of some cams that have a
two marks…180 apart. When removing one must be careful to
note which mark…and note cam positions to be correct, for
both R and R.
It will be interesting to find out about my flywheel as
installed. I was not the one that set up and timed the
dizzy a long time ago…guess they figured it out. I had
thought my wiring on the distrib cap was as original…maybe
it too is 180…my rotor contact when to #6 front…has the
rotor toward the front right corner of the block…is that
where 'y’all have it? (standing at side looking at it…it is
about 1-2 oclock)
Nick–
Nick53XK120S
Spokane WA, United States
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In reply to a message from Nick53XK120S sent Mon 29 Aug 2016:
Nope…IF the dizzy drive shaft had been installed per the
Manual, the rotor would be pointing at either the 3 o’clock
position, or the 9 o’clock position…as viewed from the
side of the block. The slot in the dizzy drive is supposed
to be parallel to the block centerline when 1/6 are at TDC,
so there is not much knowledge to be gained from persuing
this avenue of inquiry since your dizzy drive (and other
parts) were not installed ‘‘by the book’’. Does your damper
have visible timing marks?..and are they reliable?(not
having slipped from the factory setting)…or the timing
pointer itself may be ‘‘adjustable’’…like on my engine.
I’m not familiar with any possible differences between the
120 and (my)140 vis-�-vis timing marks.–
The original message included these comments:
it too is 180…my rotor contact when to #6 front…has the
rotor toward the front right corner of the block…is that
where 'y’all have it? (standing at side looking at it…it is
–
Lee140FHC
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Lee;
The XK120 has NO timing marks on the harmonic balancer/
damper. Thus no adjustable indicator. All we (120 owners)
have is the TDC Mark on the flywheel, visable thru a little
“hole” (aka Window). Interestingly, the distributor is on
the left side of the engine, the TDC Mark is ONLY visable
on the right side of the engine. As one (USA) auto insurance
company TV ad says: “Perfect!” Go Figure!!
Charles #677556.
Does your damper----- Original Message -----
From: “Lee140FHC”
have visible timing marks?..and are they reliable?(not
having slipped from the factory setting)…or the timing
pointer itself may be ‘‘adjustable’’…like on my engine.
I’m not familiar with any possible differences between the
120 and (my)140 vis-�-vis timing marks.Lee140FHC
In reply to a message from cb@risebroadband.net sent Mon 29 Aug 2016:
I think friend Charles has his lefts and rights reversed. Or
perhaps he has his engine in backwards. 
Anyway, something that Nick should be made aware of, is that
although the arrow indicates that the 1 & 6 pistons are at
top dead center, the arrow itself is not, it is offset to
the left; therefore, when you crawl underneath to put a
white paint mark 180 degrees from the arrow, it will not be
at the dead center below the crank center, it will be offset
to the right.
The distributor drive gear has 20 teeth so the shaft can be
installed the correct factory way as Lee described, plus 19
other ways, all of which can be made to work ok if you turn
the distributor body and/or shift the wires around.
Another thing to note is the rotor drive shaft can be
installed two ways in the distributor body, so yet another
reason people may find their rotors pointing different ways
even if they follow the instructions in the manual.
I came across this just last week when I went to change my
distributor because I was concerned about the little flex
wire inside, and found my spare was 180 off from my original.–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
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I think friend Charles has his lefts and rights reversed. Or
perhaps he has his engine in backwards.
Rob R;
Yeah, I did!
Correctly speaking, Left and Right (in the USA) is
determined when being seated in the vehicle, facing
forward…
In my case, I was seated at the computer with my head
“up and locked” 
As to your comment about the distributor being able
to be installed “both” ways… Technically this is incorrect…
there is an off-set in the drive dog that is “suppose” to
prevent an “accidental” 180* out installation… That said,
apparently there were a LOT of heavy-handed “grease-
monkeys” back in the '50’s and '60’s who did NOT
understand the word “Finesse” when applied to “Foreign
Car” repairs, but fully understood “BFH”!! I guess that
works on Dee-Troit Iron, but said “Finesse” was sure as
hell taught to me!! (still have the “knuckle bumps” on my
head to prove it!)… Even if I can’t tell my left from right ;-}
BTW, My Distributor Drive STILL only fits one way ;-}
Charles #677556.----- Original Message -----
From: “Rob Reilly”
ah - but the pin securing to the drive dog to the rotating shaft appears
to be centered and the dog could be positioned the wrong way round -
unlikely but a PO might have done it - we all know not to underestimate
the stupidity of PO’sOn 8/30/2016 1:01 PM, cb@risebroadband.net wrote:
----- Original Message ----- From: “Rob Reilly”
I think friend Charles has his lefts and rights reversed. Or
perhaps he has his engine in backwards.Rob R;
Yeah, I did!
Correctly speaking, Left and Right (in the USA) is
determined when being seated in the vehicle, facing
forward… In my case, I was seated at the computer with my head
“up and locked”
As to your comment about the distributor being able
to be installed “both” ways… Technically this is incorrect…
there is an off-set in the drive dog that is “suppose” to
prevent an “accidental” 180* out installation… That said,
apparently there were a LOT of heavy-handed “grease-
monkeys” back in the '50’s and '60’s who did NOT understand the word
“Finesse” when applied to “Foreign
Car” repairs, but fully understood “BFH”!! I guess that
works on Dee-Troit Iron, but said “Finesse” was sure as hell taught to
me!! (still have the “knuckle bumps” on my
head to prove it!)… Even if I can’t tell my left from right ;-}
BTW, My Distributor Drive STILL only fits one way ;-}
Charles #677556.
The last one I fitted was left of centre so only fitted one way as it block the distributor from seating all the way home properly.
DJ
ah - but the pin securing to the drive dog to the rotating shaft appears to be centered and the dog could be positioned the wrong way round - unlikely but a PO might have done it - we all know not to underestimate the stupidity of PO’sOn 30 Aug 2016, at 19:00, Bruce Cunningham bcunning@gmavt.net wrote:
On 8/30/2016 1:01 PM, cb@risebroadband.net wrote:
----- Original Message ----- From: “Rob Reilly”
I think friend Charles has his lefts and rights reversed. Or
perhaps he has his engine in backwards.Rob R;
Yeah, I did!
Correctly speaking, Left and Right (in the USA) is
determined when being seated in the vehicle, facing
forward… In my case, I was seated at the computer with my head
“up and locked”
As to your comment about the distributor being able
to be installed “both” ways… Technically this is incorrect…
there is an off-set in the drive dog that is “suppose” to
prevent an “accidental” 180* out installation… That said,
apparently there were a LOT of heavy-handed “grease-
monkeys” back in the '50’s and '60’s who did NOT understand the word “Finesse” when applied to “Foreign
Car” repairs, but fully understood “BFH”!! I guess that
works on Dee-Troit Iron, but said “Finesse” was sure as hell taught to me!! (still have the “knuckle bumps” on my
head to prove it!)… Even if I can’t tell my left from right ;-}
BTW, My Distributor Drive STILL only fits one way ;-}
Charles #677556.
Bruce C;
That is true… the Engine’s Dist Drive Shaft could have
been installed 180* out rendering the “#6” position bassackwards from where
it should be…
Likewise, as Rob R and I mentioned, some PO or buffoon
“shade-tree” could have unknowingly tried to insert the offset
drive dog 180* out and, encountering a balky fit, simply
MADE the drive dog fit into the drive shaft… I’ve seen a
few said drive shafts that were so “wallered out” it was a
wonder the shaft could even turn the distributor and keep
the firing with a cylinder or two of correct timing!!
Charles #677556----- Original Message -----
From: “Bruce Cunningham”
ah - but the pin securing to the drive dog to the rotating shaft appears
to be centered and the dog could be positioned the wrong way round -
unlikely but a PO might have done it - we all know not to underestimate
the stupidity of PO’s
In reply to a message from cb@risebroadband.net sent Tue 30 Aug 2016:
Sorry I wasn’t clear on what I meant by ‘‘rotor drive shaft’’.
This is the 408999 Cam Assembly shaft that does the point
lifting and the rotor plugs in to. This can be assembled to
the 415729 Advance Weights on the 410620 Action Plate two
ways 180 degrees apart.
This is what I found on my spare distributor, when I put it
in I saw the rotor was 180 out from where the original had it.
In this case nothing to do with the offset driving dog at
the bottom end.–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
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Even easier than that is to assemble the bottom and top halves of the
distributor the wrong way around. The shaft with the driven dog is only
connected to the rotor shaft through a screw and a couple of springs and
weights.
Mike Eck
New Jersey, USA
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2>
ah - but the pin securing to the drive dog to the rotating shaft appears
to be centered and the dog could be positioned the wrong way round -
unlikely but a PO might have done it - we all know not to underestimate
the stupidity of PO’s
In reply to a message from Mike Eck sent Tue 30 Aug 2016:
eeeeegaaaaad…!! lotsa variables of what the DPO and
cohorts may have done…can’t wait to check it all out and
discover…if indeed I can. well one thing…as stated in the
Jaguar Service Manual overleafside of very first page at
bottom:
‘‘NOTE Throuhout this Manual reference to right hand and
left hand I made assuming the driver to be seated in the car
and facing forward’’ One and only one right hand side of the
car…and this view should be applied to referring to clock
and counter clock of flywheel and damper and the rotating
parts.
so thanks all good info for when I next hang upside-down…
(as from the view of a right side up person) in the engine
bay.
Nick–
Nick53XK120S
Spokane WA, United States
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In reply to a message from Nick53XK120S sent Tue 30 Aug 2016:
Egad! indeed. When I set my engine up after the rebuild I
used a dial indicator to set #1 at TDC and then discovered
that the flywheel timing arrow wasn’t visible through the
bell housing window. No, it wasn’t 180 degrees out, it was
just out of view, about 2 teeth ‘‘late’’. Beware.
Bruce Wright#674699–
The original message included these comments:
eeeeegaaaaad…!! lotsa variables of what the DPO and
–
Bruce Wright XK120 OTS #674699
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In reply to a message from Bruce Wright sent Thu 1 Sep 2016:
Uh oh, that is rather disconcerting…though my rebuilt
short block seems to be spot-on…so far…but I did plan
on using the ‘‘piston-stop’’ method OR a dial indicator to
make sure BOTH my damper and F/W are properly
marked/located. (My engine has the head removed). This is
the first I’ve heard of a F/W being ‘‘off’’.–
The original message included these comments:
just out of view, about 2 teeth ‘‘late’’. Beware.
–
Lee140FHC
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In reply to a message from Lee140FHC sent Thu 1 Sep 2016:
as to flywheel being ‘‘off’’…i suppose anything could be done
incorrectly…even at factory but more likely by a later DPO.
So if ‘‘off’’ any later tuner setting timing would have to
know…or be way off. All this the reason I started checking
mine for confirmation…before doing some work and a new
distrib install. Whatever I find, I feel I should engrave on
a metal plate to attach in an obvious place.
by the way interesting thread on spark plugs on the e type
forum…as well as here.
Nick–
Nick53XK120S
Spokane WA, United States
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