[xk-engine] Electronic ignition

Hi guys,

Has anyone had any experience fitting electronic ignition to an XK engine?
And if so, are there any secrets one should know about before launching
oneself into the conversion?

Thanks in advance

Shane
65 3.4 S Type

Shane Jarvis wrote

Has anyone had any experience fitting electronic ignition to an XK engine?

Shane,

 I have been running a Pertronix Ignitor in my 3.8S for several years.  

It is a small Hall effect sender that replaces the points and condenser
inside the distributor. It is easy to install and you can convert back to
points if it fails. I am also running an MSD 6AL spark box which provides
higher voltage and multiple sparks below 3000 rpm. It is really for high
performance applications and it allows a much larger plug gap. I have used
them on several cars and found that the biggest advantage is improved
throttle response and idling, especially when using a longer duration
camshaft that does not like to idle well. The are other systems available
from Lumenition (magnetic and optical), Allison and Mallory(optical). Most
of these require you to convert to negative ground. You can also use the
complete system from a Series III XJ-6.

Paul Saltwick
3.8S Type

Shane,

Itā€™s a gosh darned easy thing to do! Iā€™ve got aā€™59 MK-I with and MSD 6-T
racing ignition with rev limiter and computerized distributor advance(I
always get carried away). In my case I am running a 4.2l instead of a 3.4,
but all modifications I did should work on any XK engine (as far as Iā€™ve
found the distributor ā€œholeā€ and drive is the same on 3.4, 3.8 and 4.2
blocks).

First, the distributor. Iā€™ve swapped the points type unit for a magnetic
pickup style from a Series III XJ-6.

Second, mechanical advance. Because I used an electronic advance box (more
than is required) Iā€™ve locked the mechanical advanced weights so they do not
move. More-or-less Jaguar uses a similar advance curve on all the XK engined
cars (this is approximate: initial advance 10 degrees @ 500 RPM, 20 degrees
@ 1800 RPM). With this in mind a correctly operating mechanical advance
(weights not stuck) will work great with no changes!

Third, ignition module. I chose an MSD multi-spark box (lots of other
modifications made to the engine and more money than sense), but the great
thing about doing the distributor swap is you can just plug in the standard
Series III XJ-6 ignition box or just about any other aftermarket ignition
(almost all of them support magnetic pickups). The other nice thing about
the XJ-6 box is no other components, like a ballast resistor.

Fourth, installation. With a careful installation you can pretty much hide
changes to all but the most discriminating eye. The magnetic pickup
distributor does not have the ā€œmicrometerā€ adjustment on it, the cap has
screws instead of clips, and push on wires instead of ā€œscrewā€ on. With
careful wire routing the cables are easily hidden and the ignition box can
be mounted pretty much anywhere. The injected XJ-6 has the ignition module
mounted right on the intake plenum, thus under-hood heat is not a huge
factor, hide the box wherever it is out of sight! In my case, the ignition
and advance computer are mounted inside the cabin behind the glove box and
connected with a ā€œcustomā€ wiring loom that follows the existing engine
harness through the firewall.

There you have it!

I have not tried any of the ā€œopticalā€ type units that you use to retrofit a
points type distributor, Iā€™m sure they work fineā€¦ but when it comes time
to replace a failed component the Series III XJ-6 stuff is very easy to
find, not any more expensive and, having been installed on thousands of
cars, well tested and proven.

Iā€™d speculate with a little effort one could swap the internal shaft and
plate (where the points / magnetic pickup mount) from a new distributor with
the older style and keep the external appearances like original.

Mike W-----Original Message-----
From: Mike Waldron
Sent: Wednesday, February 02, 2000 9:34 PM
To: ā€˜Shane Jarvisā€™
Subject: [xk-engine] Electronic ignition

-----Original Message-----
From: Shane Jarvis [mailto:jarviss@optusnet.com.au]
Sent: Wednesday, February 02, 2000 2:04 AM
To: xk-engine@jag-lovers.org
Subject: [xk-engine] Electronic ignition

Hi guys,

Has anyone had any experience fitting electronic ignition to an XK engine?
And if so, are there any secrets one should know about before launching
oneself into the conversion?

Thanks in advance

Shane
65 3.4 S Type

Mike Waldron wrote:

Iā€™ve got a '59 MK-I with and MSD 6-T racing ignition with rev limiter and
computerized distributor advanceā€¦ Iā€™ve swapped the points type unit for a
magnetic
pickup style from a Series III XJ-6ā€¦

Mike:

 I am curious about your ignition set up and have a couple of questions 

if you donā€™t mind. Which XJ-6 distributor did you use (45DM6 ?) and do you
have it directly connected to the MSD without the Lucas ignition amplifier ?
Are you still using the vacuum advance on the distributor? Which timing
computer are you using and what is you total advance?
I am using the 22D6 distributor which has 24 degrees of mechanical
advance with a static setting of 12 degrees for a total of 36 degrees. The
vacuum advance adds 9 degrees. With the vacuum connected, I get around 44
degrees of total timing at 3000 rpm with an advance timing light. This is a
road car with 9:1 compression and a mild cam with no signs of detonation. Do
you know the total timing specification (with vacuum connected) for the 45DM6
distributor ? I have a programmable EFI system on my 3.8S which is fuel only
and I am thinking about upgrading to programmable fuel and ignition and
perhaps doing away with the distributor entirely with a coil pack and a crank
trigger. Thanks

Paul Saltwick
3.8S Type

I chose MSD because my brother-in-law used to race a Formula 2000 car and
now runs in the Nascar Craftsman Super Truck Series (both carbureted cars)
and every time Iā€™d nose around in the pits 90% of the teams used MSD. I
figured if it was good enough for them, it ought to be good enough for my
street usage! Iā€™ve had the MSD stuff for quite a while and they now have
newer models (I think some that include both the timing computer and
ignition in one box).

Iā€™m using a Lucas 45DM6 Distributor with standard vacuum advance and the
centrifugal advance locked (Iā€™m unsure of the original mechanical advance of
this distributor) directly connected to an MSD Programmable Timing Computer
#8981 (it has a magnetic pickup input) that is connected to an MSD 6-T
Multispark Ignition (it also has a magnetic pickup input if you choose not
to use a timing computer).

My engine is a mid-eighties XJ-6 4.2l block with 9:1 pistons. Iā€™m using an
injected head (bigger valves than the non-injected head) from the
early-eighties without air injection ports. Iā€™ve got the cams, cam covers,
dual HD-8 carburetors and intake manifolds from a '67 420. The exhaust
manifolds are from the original 3.4l MK-I engine. The intake ports on the
injected head are larger than the 420 so the intake was ā€œportedā€ to match
the head. The exhaust ports are the same size.

I compared various timing settings from carbureted Jaguars built in the
sixties (before pollution control). Generally they were set to 10 degrees
static with another 10 degrees centrifugal and 9 degrees vacuum. This is
what the pre-emissions control 4.2l E-Types were set to. Interestingly
enough, Bentleyā€™s Complete Official Jaguar ā€œEā€ manual includes a section on
race preparation of the E-Type. In that section no timing changes are
recommended. The Series 2 ā€œEā€ with Stromberg carburetors had static of 5
degrees with mechanical of 36 degrees, for a total of 41 degrees at 4400
RPM!

Why am I telling you all this? I concluded Jaguar probably knew what they
were doing and since they had thousands of cars to experiment with and Iā€™ve
only got a few, Iā€™d more-or-less go with their recommendations. I figure my
engine is not all that much different in itā€™s running characteristics than a
4.2l Series One ā€œEā€. With this in mind, Iā€™m running 10 degrees static, 15
degrees ā€œmechanicalā€ (generated by the timing computer) starting at around
800 RPM and fully advanced around 1800 RPM (just about the Eā€™s curve) with 9
degrees vacuum (pulled from the HD-8ā€™s vacuum port which means no vacuum at
idle, just when the throttles are open).

So I guess Iā€™m running a total advance, including vacuum, of 34 degrees.
Iā€™ve run mine up around the 44 degrees total that you are running and what I
found was, although it seemed to improve performance a little without
detonation, that my fuel economy was about the same and the engine sounded
ā€œharshā€. Since my MK-I is my everyday transportation, longevity and
comfortable, QUIET motoring is important.

All-in-all, the design of the combustion chamber is the primary factor in
the propagation speed of the flame front during combustion(I read that in a
fancy engine build book I got). Since the superb design of the XK engines
ā€œpent roofā€ head, which helps to eliminate detonation, is the same on all
4.2ā€™s the burn speed should be similar. As long as the chamber pressures
donā€™t create detonation, somewhere around the factory timing settings should
work pretty darn good. Since your running ā€œmildā€ cams, your car should
breath better. Generally in that situation one would retard the timing a bit
because of higher chamber pressures (thatā€™s why it increases HP).

O.K. hereā€™s the last thing Iā€™ve got to say. How come it was such a big deal
when us Americans invented the ā€œhemiā€ head (only 10 or 15 years after Jaguar
did it)?

Mike Waldron wrote:

All-in-all, the design of the combustion chamber is the primary factor in
the propagation speed of the flame front during combustion (I read that in a
fancy engine build book I got). Since the superb design of the XK engines
ā€œpent roofā€ head, which helps to eliminate detonation, is the same on all
4.2ā€™s the burn speed should be similar. As long as the chamber pressures
donā€™t create detonation, somewhere around the factory timing settings should
work pretty darn good. Since your running ā€œmildā€ cams, your car should
breath better. Generally in that situation one would retard the timing a bit
because of higher chamber pressures (thatā€™s why it increases HP).

Hello Mike,

 Thanks for the information.  I my case, I think it's the fuel injection, 

the cam and the wider plug gap of the MSD that allows more advance, although
Iā€™m only about 5 degree above stock for the 9:1 and about the same as the 8:1
distributor. I think the real benefit of the MSD for a street car is
improved low speed performance. A high performance cam with longer overlap
actually produces less chamber pressure at lower speed because of the late
intake valve closing. This is why you lose low speed torque in exchange for
better high speed performance with high performance cams. Most detonation on
a street car occurs at low speed WOT.
The XK engine has a Hemi head and a VIA (valve included angle) of 70
degrees. A ā€œpent roofā€ head (invented in 1913, nothing is newā€¦), which is
a much better design, has four valves per cylinder, and a much narrower VIA
for a more compact chamber. This was the state of the art in racing engines
until 1923 when Fiat introduced supercharging making the four valves less
important and the two valve Hemi head became popular. The XK engine is very
similar to the 1919 Ballot in bore and stroke and valve mechanism (although
with only two valves). By comparison, the Jaguar chamber is quite large,
that is why the pistons need a big dome to get a decent compression ratio.
On later Hemi designs, like the Lotus twin cam head, the VIA was reduced to
54 degrees to make a more compact chamber. On a true ā€œpent roofā€, like a
Cosworth DFV, the VIA in only 32 degrees and high compressions can be made
with flat top pistons. These engine need less advance than the Hemi design.
The only thing that saves the hemi is the central spark plug. In any event,
I think the XK engine was a nice design in 1946 for a road car, but the sad
truth is that the combustion chambers on a new disposable Honda would have
made these guys drool with envy. Not to mention the 8000 rpm. Just a few
thoughts.

Paul Saltwick

Mike,

your vacuum advance will not be applied at all under WOT (it is for
cruising economy purposes only), so you are running 25 degrees timing
all in at 1800 when you nail it. I guess thatā€™s OK but I think you are
probably giving up quite a few ponies. The reason your engine sounded
harsher with more advance was probably because it was making
significantly more power. Most modern efficient combustion chambers
need more than 30 degrees, with older and less efficient designs (like
old BB Chevys with domed pistons) needing up to and even over 40. I
always start with 36 and work from there.

You have short duration cams which build good chamber pressure at low
RPM so you donā€™t need to go crazy with static advance (its probably fine
where it is), and you shouldnā€™t tip the advance in too quick (maybe all
in by 2500), but I would try at least 32-34 total. If you have a spare
dizzy you could get one set up static 10, +mech 22 by 2500 rpm, with
8-10 vacuum on top (giving 32 with WOT and 40ish cruise) and do a back
to back test.

Cheers, Andrew Robertson

Mike Waldron wrote:>

I chose MSD because my brother-in-law used to race a Formula 2000 car and
now runs in the Nascar Craftsman Super Truck Series (both carbureted cars)
and every time Iā€™d nose around in the pits 90% of the teams used MSD. I
figured if it was good enough for them, it ought to be good enough for my
street usage! Iā€™ve had the MSD stuff for quite a while and they now have
newer models (I think some that include both the timing computer and
ignition in one box).

Iā€™m using a Lucas 45DM6 Distributor with standard vacuum advance and the
centrifugal advance locked (Iā€™m unsure of the original mechanical advance of
this distributor) directly connected to an MSD Programmable Timing Computer
#8981 (it has a magnetic pickup input) that is connected to an MSD 6-T
Multispark Ignition (it also has a magnetic pickup input if you choose not
to use a timing computer).

My engine is a mid-eighties XJ-6 4.2l block with 9:1 pistons. Iā€™m using an
injected head (bigger valves than the non-injected head) from the
early-eighties without air injection ports. Iā€™ve got the cams, cam covers,
dual HD-8 carburetors and intake manifolds from a '67 420. The exhaust
manifolds are from the original 3.4l MK-I engine. The intake ports on the
injected head are larger than the 420 so the intake was ā€œportedā€ to match
the head. The exhaust ports are the same size.

I compared various timing settings from carbureted Jaguars built in the
sixties (before pollution control). Generally they were set to 10 degrees
static with another 10 degrees centrifugal and 9 degrees vacuum. This is
what the pre-emissions control 4.2l E-Types were set to. Interestingly
enough, Bentleyā€™s Complete Official Jaguar ā€œEā€ manual includes a section on
race preparation of the E-Type. In that section no timing changes are
recommended. The Series 2 ā€œEā€ with Stromberg carburetors had static of 5
degrees with mechanical of 36 degrees, for a total of 41 degrees at 4400
RPM!

Why am I telling you all this? I concluded Jaguar probably knew what they
were doing and since they had thousands of cars to experiment with and Iā€™ve
only got a few, Iā€™d more-or-less go with their recommendations. I figure my
engine is not all that much different in itā€™s running characteristics than a
4.2l Series One ā€œEā€. With this in mind, Iā€™m running 10 degrees static, 15
degrees ā€œmechanicalā€ (generated by the timing computer) starting at around
800 RPM and fully advanced around 1800 RPM (just about the Eā€™s curve) with 9
degrees vacuum (pulled from the HD-8ā€™s vacuum port which means no vacuum at
idle, just when the throttles are open).

So I guess Iā€™m running a total advance, including vacuum, of 34 degrees.
Iā€™ve run mine up around the 44 degrees total that you are running and what I
found was, although it seemed to improve performance a little without
detonation, that my fuel economy was about the same and the engine sounded
ā€œharshā€. Since my MK-I is my everyday transportation, longevity and
comfortable, QUIET motoring is important.

All-in-all, the design of the combustion chamber is the primary factor in
the propagation speed of the flame front during combustion(I read that in a
fancy engine build book I got). Since the superb design of the XK engines
ā€œpent roofā€ head, which helps to eliminate detonation, is the same on all
4.2ā€™s the burn speed should be similar. As long as the chamber pressures
donā€™t create detonation, somewhere around the factory timing settings should
work pretty darn good. Since your running ā€œmildā€ cams, your car should
breath better. Generally in that situation one would retard the timing a bit
because of higher chamber pressures (thatā€™s why it increases HP).

O.K. hereā€™s the last thing Iā€™ve got to say. How come it was such a big deal
when us Americans invented the ā€œhemiā€ head (only 10 or 15 years after Jaguar
did it)?

Andrew,

Empirical data!!!

As per your suggestion, I decided to experiment with my timing. Fortunately,
with my timing computer, this was easy.

Hereā€™s the setup:

In my MK-I, with a BW66 automatic and 3.54 axel I ran several 0 to 60 time
tests, utilizing my local Interstate entrance ramp (Iā€™ve got one that is
straight, flat and long). I used a stopwatch in conjunction with a GPS unit
Iā€™ve got in the car (it has a speed indicator that is very accurate). Watch
out NHRA, here I come.

I set the static timing to 12 degrees.

I set the timing computer to start advancing at 1000 RPM with full advance
at 2200 RPM.

I varied the max advance from 20 to 40 degrees, in 5 degree increments.

Here are the results:

20 degrees 14.1 seconds
25 degrees 13.8 seconds
30 degrees 13.0 seconds
35 degrees 12.8 seconds
40 degrees 13.2 seconds

Although this test would never pass peer review, it ought to be good enough
for us greasy fingernail guys. The ā€œbestā€ spot is around the 32 to 34
degrees you suggest. I was surprised that the times were so close
considering such a wide variation of advance. I left my car at 30 degrees, 5
degrees more than I usually run. Iā€™ll report back in regards as to any
mileage improvement.

Now hereā€™s my question. Having looked through all my Jaguar manuals in
regards to carbureted 4.2l engines from the early sixties to the late
seventies, why do most of them say a max advance of 20 degrees (Series One
E-Type {including race preparation suggestions}, MK-II, 420 and XJ-6)? Did
possible longevity issues outweigh 1.3 seconds of 0 to 60 improvement?

Mike

Mike Waldron wrote:

Now hereā€™s my question. Having looked through all my Jaguar manuals in
regards to carbureted 4.2l engines from the early sixties to the late
seventies, why do most of them say a max advance of 20 degrees (Series One
E-Type {including race preparation suggestions}, MK-II, 420 and XJ-6)? Did
possible longevity issues outweigh 1.3 seconds of 0 to 60 improvement?

Mike:

The specifications in my Jaguar manual are in degrees of ā€œdistributorā€
advance, when the distributor is placed on a distributor calibration machine.
This is half of ā€œcrankshaftā€ advance, since the distributor turns at half
the crank speed. So the 3.8 specs of 13 for the 9:1 and 19 for the 8:1, are
26 and 38 BTDC ā€œcrankshaftā€ advance. Some manuals do not give distributor
data and only specify a ā€œcrankshaftā€ advance at a specific rpm, which may or
may not be maximum advance.

Paul Saltwick

Paul,
Iā€™ve been observing this conversation with keen interest. I drive an 85
XJ6 (US Spec) in which Iā€™ve installed 9:1 pistons. Iā€™m trying to set the
engine up for best all around performance. Judging from your conversation, I
think Iā€™m on track with modifying my US distributor (41912 46DM6), which only
had 14 deg at the crank advance (Note: European 41913 46DM6 distributors 20 -
22 deg at crank). With the 8:1 pistons, the US spec called for 17 static,
which I canā€™t run with 9:1 pistons. My objective is to get it up to about 22
deg, then set static to 10 deg, I have it up to 18 now. My cam is advanced 2
deg, and Iā€™m running my static at 14 deg in order to give me 32 total
mechanical.
My question at this time is what kind of spark plugs are you-all running
on these, and are your cams advanced? Remember Iā€™ve got all that emission
control garbage, but I think I can make it all work.

Charles
85 XJ6
Converse, TX

In a message dated 02/07/2000 7:32:35 AM Central Standard Time,
Tlsalt@aol.com writes:

<< Subj: [xk-engine] Electronic ignitionDate: 02/07/2000 7:32:35 AM Central Standard Time
From: Tlsalt@aol.com
Sender: owner-xk-engine@jag-lovers.org
To: xk-engine@jag-lovers.org

Mike Waldron wrote:

Now hereā€™s my question. Having looked through all my Jaguar manuals in
regards to carbureted 4.2l engines from the early sixties to the late
seventies, why do most of them say a max advance of 20 degrees (Series One
E-Type {including race preparation suggestions}, MK-II, 420 and XJ-6)? Did
possible longevity issues outweigh 1.3 seconds of 0 to 60 improvement?

Mike:

The specifications in my Jaguar manual are in degrees of "distributor" 

advance, when the distributor is placed on a distributor calibration
machine.
This is half of ā€œcrankshaftā€ advance, since the distributor turns at half
the crank speed. So the 3.8 specs of 13 for the 9:1 and 19 for the 8:1, are
26 and 38 BTDC ā€œcrankshaftā€ advance. Some manuals do not give distributor
data and only specify a ā€œcrankshaftā€ advance at a specific rpm, which may or
may not be maximum advance.

Paul Saltwick

Michael Rogers wrote:

ā€œHowever if we were to have a lessor angle head there would also be less room
for valves. The modern motors have a BIG bore and small stroke and so can
have comparatively BIG valves for the ccā€™sā€

Andā€¦? In the context of the discussion, the spark advance requirement
for the XK engine, the further apart you place the valves, the larger the
combustion chamber and the probability it will need more ignition advance for
optimum power. It started with a comment that 25 degrees was enough, but it
seems 34-36 degrees is needed for the XK engine. Whatā€™s your experience? The
only thing Iā€™ve found in print is the ā€œPiper Tuning manualā€ which suggests 40
degrees of total advance for the XK engine. I am running 36 on a road car
with no signs of detonation. Perhaps the best advice for these engines (for
a road car) would be to advance until it is pinging slightly under load and
back off a few degrees, then do a spark plug check.

Paul Saltwick

In a message dated 02/11/2000 6:30:09 AM Pacific Standard Time,
Tlsalt@aol.com writes:

<< Perhaps the best advice for these engines (for
a road car) would be to advance until it is pinging slightly under load and
back off a few degrees, then do a spark plug check.

What Iā€™m interested in doing --and what also answers the question ā€“ is to
install one of the electronic ignition systems that incorporates a KNOCK
sensor. When it hears a knock, it pulls a couple of degrees of advance out.
If it doesnā€™t hear another, it advances it a bit and so on therby providing
as much advance as possible without knocking (much).
This is extremely important with one of our noisy cars-like mine where we
canā€™t hear the pinking under full chat. They have used them on cheap lumps
so they should be economically available.
They promote the theory that the largest amount of advance possable is
desirable, something Iā€™ve always found when dynos were used and has
frequently been offered in olde tuneup manuals that suggested that after
setting it to published specs to road test and fine tune it for optimal
settings.
Weā€™re dealing with olde lumps guys and there probably have been many
variables introduced to them such as changed deck heighth, shaved heads,
pistons with differing heights and even changed cam timing or settings. All
these influence the optimal timing.
regards;
Michael Rogers

Michael Rogers wrote

What Iā€™m interested in doing --and what also answers the question ā€“ is to
install one of the electronic ignition systems that incorporates a KNOCK
sensor. When it hears a knock, it pulls a couple of degrees of advance out.
If it doesnā€™t hear another, it advances it a bit and so on thereby providing
as much advance as possible without knocking (much).

Michael,

Although I have yet to fool around with knock sensors,  I have installed 

a programmable fuel injection system on an XK engine, and read all of the
text on engine management systems I could find. They do not recommend using
a knock sensor to build a spark map, just like they do not recommend using an
O2 sensor feedback loop to adjust for incorrect fuel mapping. Apparently the
ECU programs, especially OEMā€™s, are very conservative about ending ignition
knock and they retard the timing significantly after ā€œhearingā€ it. Because
of the ā€œhysteresis of knockā€ ( a former girl friend) , it take a significant
amount of retard to stop detonation once it starts. The systems may retard
the ignition 8 degrees to stop the detonation caused by 2 degrees of advance.
This does more harm than good in terms of performance. The recommended
procedure would be to find the knock limit and program the ignition to avoid
the knock in the first place for maximum performance. I do not know of an
ECU with an adjustable spark retard parameter for the knock sensor. Most of
them allow you to set the 02 sensor parameter if your after something other
than keeping a catalytic converter happy. Although we are getting close,
the era of ā€œplug and playā€ engine management computers is not really here
yet. It should be possible to design a system with a wide band O2 sensor and
a knock sensor which would be ā€œself learningā€. After a few full throttle
runs, the ideal fuel map and ignition curve could be determined by the ECU.
The computer power is here, I donā€™t think the sensors are up to it yet,
especially for WOT under load.

Paul Saltwick

Hi Michael,

A couple of thoughts on the ignition thing.

  1. I have not had any real experience with dynos but have read in
    several places that dyno optimised timing can be too agressive for
    actual driving. This is usually put down to the small amount of time
    that the engine runs under load at the maximum timing, not giving
    sufficient time for the combustion chamber to stabilise thermally with
    the new (higher) advance. Some dyno operators even seem to consider
    flash type readings appropriate where they just twist the distributor
    around until they get max power - not a real world situation at all.

  2. Iā€™m not 100% sure of this, but Iā€™m pretty sure knock sensors are
    essentially microphones with a band pass filter to isolate the typical
    noise of engine knock. I researched construction of a knock sensor kit
    and there were specific warnings/disclaimers outlining that the kit
    would not work properly on a (mechanically) noisy engine. Given the
    mechanical caucophony that often occurs in the valvetrain of an XK
    engine when valve lash gets a bit out (or a bit of piston noise when
    cold etc), coupled with the fact that you are considering using a
    generic knock sensor not tailored for the harmless mechanical noise
    produced by the XK, I would have reservations about a knock sensorā€™s
    ability to distinguish actual knock consistently.

  3. More advance is not neccessarily better. There is usually a bit of a
    band where power does not change significantly for the addition of extra
    timing. Purely as a saftey margin against overheating or poor fuel, I
    would set the timing at the stage where extra timing made a negligible
    difference. This may be 2 degrees or so retarded from peak power timing
    (and may involve the ā€œsacrificeā€ of a couple of HP). Another fairly
    obvious factor often overlooked is that once a new max timing is
    established, the rest of the curve needs to be optimised. When adding
    more total timing, it is not uncommon to run into detonation problems at
    peak torque rpm because the static has been pulled up too and maybe the
    advance is maybe being tipped in too quickly.

Cheers, Andrew Robertson, New Zealand

EeeMCee@cs.com wrote:>

In a message dated 02/11/2000 6:30:09 AM Pacific Standard Time,
Tlsalt@aol.com writes:

<< Perhaps the best advice for these engines (for
a road car) would be to advance until it is pinging slightly under load and
back off a few degrees, then do a spark plug check.

What Iā€™m interested in doing --and what also answers the question ā€“ is to
install one of the electronic ignition systems that incorporates a KNOCK
sensor. When it hears a knock, it pulls a couple of degrees of advance out.
If it doesnā€™t hear another, it advances it a bit and so on therby providing
as much advance as possible without knocking (much).
This is extremely important with one of our noisy cars-like mine where we
canā€™t hear the pinking under full chat. They have used them on cheap lumps
so they should be economically available.
They promote the theory that the largest amount of advance possable is
desirable, something Iā€™ve always found when dynos were used and has
frequently been offered in olde tuneup manuals that suggested that after
setting it to published specs to road test and fine tune it for optimal
settings.
Weā€™re dealing with olde lumps guys and there probably have been many
variables introduced to them such as changed deck heighth, shaved heads,
pistons with differing heights and even changed cam timing or settings. All
these influence the optimal timing.
regards;
Michael Rogers

Hi there! Well it is 18 years later from when this thread was started and ECU technology has arrived! Has anyone had any success at installing a knock sensor in their XK engine? I am doing a complete rebuild of my engine and will be going with a EFI set-up, the ECU that I am looking at can handle 2 channel knock sensors. With all the horror stories of problems with knock when bumping up the compression, it seems like the knock sensor would be a nice level of protection to add.

Iā€™m still hear. The tough thing is the XK is noisy, but I would try a bridge between two head studs and see what you hear.

Words to live by, and why that position is not likely to work, certainly w/o TONS of researchā€¦

"OEM spend a hell of a lot more money fine tuning their systems than any aftermarket system will ever come close to.

They will site the sensor where they deem best, and then they will also spend hundreds if not thousands of hours fine tuning the entire setup so it works.

Aftermarket just give you some parts and let you work awayā€¦as youā€™re trying to do now."

One quick questionā€¦ is there still a need and or preference for the MSD units if using a `full EFIā€™ system?
I assume there is?
Best regards
Phil D

I believe, in this day and age of EDIS, MSD is now a bit archaic.

Were I going to do modern EFI, I woukd ONLY utlize an EDIS system: as Andrew says, with MegaJolt, you more or less have MSD.

If Im wrong, Im sure the anoraks will set me straightā€¦:stuck_out_tongue_closed_eyes:

I would say EDIS would be more state of the art.

1 Like