[E-Type] 1970 S2 Avance Curve

In reply to a message from Jeff R sent Sat 20 Mar 2010:

The original spec for the SII EX/EM (US spec) engine is:

1400 RPM - 8 to 10 deg. (on the crank)
1800 RPM - 14 to 18 deg.
3000 RPM - 18 to 22 deg.
4000 RPM - 23 to 27 deg.

Richard Liggitt–
'70 E Roadster 1R11998, '98 XK8 Roadster, www.XKEBooks.com
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In reply to a message from Richard L. sent Sat 20 Mar 2010:

We haven’t heard from Dick V. in a while. I saved this email from
him for years ago for reference. Dick is an expert on Jag
distributors FWIW:

''An early 3.8 is the 40617, a DMBZ-6A type. Maximum centrifugal
advance at the crankshaft is 24 degrees.

There is a later 1964 22D6 equivalent, 40887. Same specs.

The 4.2 22D6, 41060 produces only 20 degrees centrifugal.

The 41207 (early S2) on the other hand produces 40 degrees
centrifugal at the crankshaft. Together with 10 degrees static,
that is 50 degrees BTDC. If that is not aggressive, I don’t know
what is.
Only EFI setups with accurate mixture control get anywhere near
that figure.

The vacuum unit under acceleration produces hardly any
contribution, it come in play during cruising and improves gas
mileage. That is why in performance setups you almost never find a
vacuum advance unit and that is why the Webers don’t have a port.

All the above distributors will fit the engine with no changes.’’

Dick Vandermeyden
San Carlos, CA–
1969 BRG OTS
Skaneateles, NY, United States
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Richard L. wrote:

In reply to a message from Jeff R sent Sat 20 Mar 2010:

The original spec for the SII EX/EM (US spec) engine is:

1400 RPM - 8 to 10 deg. (on the crank)
1800 RPM - 14 to 18 deg.
3000 RPM - 18 to 22 deg.
4000 RPM - 23 to 27 deg.

Just out of curiosity, do you have the numbers for the 4.2 S1?

I ask because a lot of folks running EDIS on the XK engine seem to use a
map with up to 38 degrees at the top rpm range.

George Cohn
'70 OTS______________________________________________________
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In reply to a message from David Ahlers sent Sat 20 Mar 2010:

David Ahler’s figures seem correct to me, but you must remember to
add the static advance to get the total advance. Thus e.g. on a
41060 the static advance should be 10 btdc, and 20 added to this
produces total centrifugal advance at c.3000 crank rpm of 30 degs
btdc–
christopher storey
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In reply to a message from christopher storey sent Sun 21 Mar 2010:

Thank you all for your very useful comments. However, I do not feel
we’ve got to the bottom of this yet.

All the manuals I have read so far direct the reader to seek other
reference documents for the advance curve of the S2 4.2 emmisioms
set up for the US and Canada. So far I have not been able to find
these references including trawling the archives.

I do however, remember reading an article ( I can’t recall where)
that the timing curve for an emmisions controlled engine with
Strombergs is significantly more advanced (up to 42 degrees
including 10 static) due to the much leaner mixture compared to the
normal SU set up of both the 4.2 and 3.8 engines.

All I’m asking is what ignition curve on the 123 JAG distributor
should a stock, emmisions controlled S2 4.2 be set to? The 123
manual says you should start by chhosing the set of four curves
appropriate to the max advance for your engine - what is this for
mine? I’ve been on the 123 web forum and cannot find an answer to
this.

I look forward to any further advice that an be offered on this.
(apart from changing to SUs!)

JeffR–
The original message included these comments:

David Ahler’s figures seem correct to me, but you must remember to


Jeff R
Camberley, United Kingdom
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In reply to a message from Jeff R sent Sun 21 Mar 2010:

Jeff,
I have an opinion based only on my experience with my S-2 which
came with a 41207. So take it with a grain of salt. It’s important
to remember that many of our Jag heads have been skimmed during
refurbishment. Therefore, your combustion chamber volume may be
different from mine. A timing curve that works for me, may not work
for you. You’re question of ‘‘which curve is best?’’ is almost moot,
apples & oranges because of engine differences.

Broad brush: you want as much advance in, as quickly as you can
without pinking. You have pinking, so cut back on advance at that
rpm. Nice to have a programable distributor!

With today’s faster burning fuel, I wouldn’t think you’d need more
than 34-36 degrees total, maybe less. Certainly going to 45 deg.
total like a stock S-2 could spell trouble. My 2 cents, feel free
to ignore.
Good luck
Dave–
1969 BRG OTS
Skaneateles, NY, United States
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In reply to a message from Jeff R sent Sat 20 Mar 2010:

Hello Jeff,

If you think you have pinging at 34 degrees, you should not be
considering increasing it to 42. There are a lot of variables in
this equation, fuel octane, coolant temp, air temp, valve timing,
actual compression, carbon, oil dilution, etc… You want to find
how much your engine can tolerate, rather than look to a book for
the answer. My experience is Hammill’s advice is too high,
especially if your engine runs hot or burns any oil.

The emission specs are sometimes counter intuitive because they
were all about meeting an artifical test. The vacuum retard was to
meet the curb idle HC test, it makes the engine run hotter and is
better off disconnected. Some of the US emission emgines went down
to 7:1 compression and the high advance was an attempt to get some
decent fuel mileage because the vacuum advance was replaced with a
retard to meet the idle test. With hotter intake air and leaner
mixtures you would expect the engine to have a lower knock limit
with the same fuel.

Mild pinging is OK, detonation is bad. My advice would be to pull
the spark plugs and inspect the insulators for aluminum flecks with
a magnifying glass. With all the plugs out, I would do a proper
compression test to see what you have. Then fill up with the
highest octane fuel you can find, test the car on a cool morning,
and see if there is a change in the noise you think is pinging. If
you can find some race gas, you will know immediately if it is
valve noise or something else. Pinging only happens under load,
immediate stops when you close the throttle, and is very
temperature sensitive. The probability of pinging is highest around
the torque peak, when VE is highest, around 4000 rpm in your
case. The noise will be quite different with a cold and hot
engine and a cold or hot day.

Paul–
The original message included these comments:

I have a US spec S2 E- Type which has its stock 9:1 compression
engine and the dual Stromberg emmisions set up.
A year or so ago a swapped out the original retard dizzi for a 123
JAG unit. The effect has been amazing - on the button starting,
faster response and a much smoother engine.
My question is that I’m not sure I have the 123 adjusted to the
correct setting. It’s presently on setting 2 which whilst fairly
aggressive at 2000 rpm maxes out at 34 degrees. On aggressive
acceleration I occasionally get a noise that sounds like a loud
metallic rattle from the valve train which I suspect to be pinging.
Could anyone advise on the best setting and if I should choose a


PS
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In reply to a message from David Ahlers sent Sun 21 Mar 2010:

Dave,

Thank you for your comments which certainly make sense.

In between sending my previous mail and receiving yours I believe
i’ve discovered the ‘stock’ answer.

This is in the ‘Exhauset Emmisions Control’ chapter of the ‘green’
Service Manual page QY.s.5. as follows:

Stroboscopic Test Data (with a static setting of 5 BTDC)

1,000 10
1,200 13 - 17
1600 22 - 26
2900 29 - 33
4400 37 - 41

This confirms my suspicions re a higher rate of advance.

My static setting is curently 10 BTDC in accordance with the 123
manual. Curve 2 of the JAG 123 which is the setting I am currenty
using is 12 @ 500-1200, 21.8 @ 2000 and 34 @ 3000 wich includes 10
static. Based on this it it would appear my timing is slightly
retarded in the lower ranges and insufficient beyond 3000.

It doesn’t explain the rattle I’m experiencing occasionally on
heavy acceleration above 2000?

Maybe curve 9 or A would be a better setting?

This would give;

12 - 21.4 and 40 @ 3600 or
12 - 22.7 - 40 @ 3300

Still puzzled?

JeffR–
Jeff R
Camberley, United Kingdom
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Hello Dave,

Keep in mind that the 41207 distributor is for
1968 (Ser 1-1/2) only. Later Ser 2 cars had a
41322 unit which is far less aggressive, see
Richard Liggitt’s data.

As has been pointed out, by now, many of our
engines have diverged due to the machining of
heads, engine blocks, etc, and the factory figures
may no longer be optimal in such situations.
Also pump fuel properties have changed drastically
since the 60’s.

For all those reasons, road testing to get the maximum
advance set to just the edge of pinging under a good
load (WOT, uphill) yields the best setting compromise.

Dick Vandermeyden
San Carlos, CA______________________________________________________
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In reply to a message from bardinet15@aol.com sent Sun 21 Mar 2010:

Thank you everyone for your advice.

As Paul and others have recommended I’ll try and keep on the safe
side so will initially reduce my present setting and first try out
the 0 and 1 curves to see if this eliminates the pinging.

If the advance curve Richard L has shown for the SII is correct it
truly is a slow curve, much less aggressive than shown in
the ‘Service Manual’. This leaves me somewhat confused as the
section in the service manual I quoted earlier is for the S2 with
Strangleburgs! What else could have changed?

Thanks for all your assistance.–
Jeff R
Camberley, United Kingdom
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Hello Jeff,

Note that the Strombergs came in January, 1968
on the Ser 1-1/2 cars together with a 41207 distributor.
The corresponding additions to the Service
Manual covered that particular period and applied
to the 41207 distributor then equipped. Somehow
the later switch to the 41322 was never clearly documented.
The comprehensive Partsbook for the Ser 2 was never
issued. I believe that very few or none 41207 distributors
came with the true Ser 2 in 1969. Richard Liggitt may be
able to shed some more light on that.

Best place to find info on the 41322 is in Technical
Service Bulletin 1G8 issued May, 1970, page 6 of 23.

Dick Vandermeyden
San Carlos, CA______________________________________________________
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In reply to a message from bardinet15@aol.com sent Sun 21 Mar 2010:

Hello Dick,

Thanks for the clarification. Do you know what else changed between
the earlier Stromberg carbed cars and the true S2s to require such
a radical change in timing?–
The original message included these comments:

Note that the Strombergs came in January, 1968


Jeff R
Camberley, United Kingdom
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In reply to a message from Jeff R sent Sun 21 Mar 2010:

Jeff,

Could the vacuum retard be involved ? Should be irrelevent at WOT,
but odd things were done initially to get by the emission
standards. IIRC it knocked back the timing 10 degrees at idle.

Paul–
The original message included these comments:

Hello Dick,
Thanks for the clarification. Do you know what else changed between
the earlier Stromberg carbed cars and the true S2s to require such
a radical change in timing?


PS
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In reply to a message from Jeff R sent Sun 21 Mar 2010:

Jeff & Dick,
My car is titled a 69 and has the 41207. vin# 1R10836

Jeff - I suspect the ‘‘art of meeting emissions’’ was a work in
progress in 1969/70 with many lessons being learned along the way.
My point is don’t be ‘‘married’’ to the early S-2 ignition specs. I
have to tell you my car was not impressive after (pistons rings
valves guides & 3 angle vj, & SU’s). I spent a lot of ‘‘blood and
treasure’’ in pusuit of the holy grail: (a ride in an older gent’s
67 ruined me) It hauled ass! My car, not even close.

I remember after the engine work AND putting the SU’s on (bolt on
50 hp!), saying ‘‘this is it’’? It ran marginally better, but
disapointing, still for sure. It still had the S-2 41207 dist which
was right on curve spec as per the manual. ''Whats another couple
hundred $$ at this point. In goes a Mallory distributor. Suddenly,
the engine was transformed. The proper advance curve made the care
go!

Take a engine warm, throttle open, compression check snd report
back. Keep playing with the advance curve options. ‘‘Your curve’’ is
in there somewhere.
Dave–
1969 BRG OTS
Skaneateles, NY, United States
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Hello Jeff,

Good question. What all changed during the
transition from S 1-1/2 to the Ser 2. This
has come up so many times in so many
contexts.

Very hard to answer, as Jaguar never issued a
proper Parts book for neither the USA Ser 1-1/2
or the Ser 2. Richard Liggitt did very extensive
research on the Ser 2, and I would think that he
is currently the best source for such info.

Max advance (crankshaft) for the Ser 1-1/2 is
10 + 2x20 = 50 degrees. For the Ser 2 it is
10 + 2x13.5 = 37 degrees. A 13 degree difference.

At the risk of going out on a limb here, my guess
is that at the time of the initial move to emission
controls in 1968, the main emphasis was on HC
and Jaguar went for the leanest mixture possible
which in turn made flame front propagation relatively
slow which had to be compensated for by more
advance. A side effect would be that combustion
temperatures were relatively high, giving rise to a
high production of NOx.

As NOx control became tighter in subsequent
years, Jaguar could have enriched the mixture slightly,
necessitating less advance and producing less NOx.
HC would rise a bit, but that compromise could meet
both emission requirements. Of course, this would
require different mixture parts in the Ser 2 Strombergs.
At this point in time, I do not know if those parts for
the Ser 1-1/2 and the Ser 2 are in fact different, due to
lack of Parts books to compare that, but it illustrates
a possible explanation of why each version is able to
run well without excessive pinging.

The Ser 2 carburetor needle is called out as: B1.A R.
No idea what the Ser 1-1/2 needle type is.

Dick Vandermeyden
San Carlos, CA______________________________________________________
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In reply to a message from bardinet15@aol.com sent Sun 21 Mar 2010:

Dick,

Thank you for your very patient and detailed explanation of how
things progressed with the S2 ignition curve - and thanks to all
you other contributors for your valuable advice. I think I now
finally understand!

At the risk of loosing any remaining goodwill, does anyone know if
there was a change in carb needle between the early S2 (with the
higher advance curve and with the ‘07’ distributor) and the later
version with the newer distributor?

Finally and perhaps more importantly, is there a recommended
needle/jet set up, stock or otherwise that would get the best out
of these carbs.

Thanks to everyone.–
The original message included these comments:

Good question. What all changed during the


Jeff R
Camberley, United Kingdom
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Hello Jeff,

A little further digging revealed that by 1970 the
Stromberg needle was specified as B1.A R, but
at the start of the Ser 2 it was B1E ( See the
Ser 2 Supplementary Information, page QY.s.8).
Some listers reported their early Ser 2 still had
the 41207 dizzy, so that may have been the
corresponding needle for that.

Jaguar has always considered what we call the
Ser 1-1/2 as a Ser 1 and no comprehensive parts
book or pertinent Supplementary Information exists.
The 1968 has a mixture cross-over channel to a
hotspot on the rear exhaust that was not carried over
to the Ser 2 as far as I know, so the 1968 model may
have used yet another carburetor needle.

Dick Vandermeyden
San Carlos, CA______________________________________________________
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In reply to a message from bardinet15@aol.com sent Mon 22 Mar 2010:

Sorry I have been out of touch. Here is a link to the
factory spec for the EX/EM engines:

http://www.xkebooks.com/images/1970%20Specs.PDF

Hope this helps.

Richard Liggitt–
'70 E Roadster 1R11998, '98 XK8 Roadster, www.XKEBooks.com
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In reply to a message from Richard L. sent Mon 22 Mar 2010:

Interesting document, in retrospect it looks like the chapter on
blood letting in a 13th century medical book.

Jeff, did you ever post which model number distributor you have and
is it clear that you were referring to the S 1 1/2 and not the S2
as in the title of this thread ?

Looking at the big picture we have:

3.8 S1 (36 max)
4.2 S1 (32 max)
4.2 S1 1/2 (41 max)
4.2 S2 (27 max)

Is the conclusion this was a failed experiment ? Did these cars
comes back with holed pistons like the 2.8’s ? I have seen similar
oddities in other makes with early emission cars, but always with a
1 or 2 point compression drop. I would think that with todays’
fuel you would have to back out at least 6 or 8 degrees, which
means recurving or a different distributor to me.

Paul–
The original message included these comments:

Sorry I have been out of touch. Here is a link to the
factory spec for the EX/EM engines:
http://www.xkebooks.com/images/1970%20Specs.PDF
Hope this helps.
Richard Liggitt


PS
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In reply to a message from bardinet15@aol.com sent Sun 21 Mar 2010:

Which is how I’ve always set timing.–
The original message included these comments:

For all those reasons, road testing to get the maximum
advance set to just the edge of pinging under a good
load (WOT, uphill) yields the best setting compromise.


Paul Wigton, steward to a '60 DKW 1000 SP, Tweety, '63 FHC!
Keenesburg, CO, United States
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