[E-Type] Timing

O.K., let’s get some good tech discussions going. I’m getting bored and
Tony Vicarage has chosen to ignore me and isn’t answering any of my
questions, so here are somethings to chew on.

1 - The Jaguar specs say that the ideal timing (for my 3.8 SI)is
10degrees BTC. I was recently speaking with someone that strongly
recommended 5 degrees BTC but no more. Retarding and going up to
10degrees After top-dead center is fine but advancing beyond 10degrees
BTC is very bad for the car. Any conjecture?
2 - I recently adjusted the mix in the carbs since one carb was running
obviously lean. The same friend went pale when he heard that I had been
running a lean. He said to always run a little rich with these cars
which might make you loose a little power but running lean is very, very
bad for the engine. My understanding was that running lean was not good
because it would just burn up the valves and plugs quicker and cause the
engine to run a little hot, but not death to an engine. Any conjecture?
3 - My friend also totally disgarded the idea of using an air-flow meter
(like Colortunes). He feels that they are entirely inaccurate with
E-Types. I must admit, I have one and have used it on my Austin-Healey
with only modest success, but never found them to really work on the
E-Type. Any conjecture?

Regards,
Mark Hicks
'64 OTS, '66 2+2, '68 AH

Snip…

1 - The Jaguar specs say that the ideal timing (for my 3.8 SI)is
10degrees BTC. I was recently speaking with someone that strongly
recommended 5 degrees BTC but no more. Retarding and going up to
10degrees After top-dead center is fine but advancing beyond 10degrees
BTC is very bad for the car. Any conjecture?
2 - I recently adjusted the mix in the carbs since one carb was
running
obviously lean. The same friend went pale when he heard that I had
been
running a lean. He said to always run a little rich with these cars
which might make you loose a little power but running lean is very,
very
bad for the engine. My understanding was that running lean was not
good
because it would just burn up the valves and plugs quicker and cause
the
engine to run a little hot, but not death to an engine. Any
conjecture?
3 - My friend also totally disgarded the idea of using an air-flow
meter
(like Colortunes). He feels that they are entirely inaccurate with
E-Types. I must admit, I have one and have used it on my
Austin-Healey
with only modest success, but never found them to really work on the
E-Type. Any conjecture?

Mark,

Item 1: I agree with your comments. Greater than 10 degrees advanced is
bad because it
catches the piston too early in the compression stroke. This can cause
broken pistons in the most extreme case. Also, remember that the higher
the
octane of the fuel the more advanced you can set the timing. Higher
octane fuel
burns slower and causes less pinging or pre detonation. If you use high
octane fuel you will probably be OK at 10 degrees before.

Item 2 : Set the mixture right in the middle. Too lean can cause burnt
valves, overheating;
too rich can cause carbon buildup.

Item 3 : There is a difference between airflow meters (such as Unisyn)
and Colortune. Colortune is
for setting the air fuel mixture. Airflow meters are for balancing the
airflow between the three carbs at idle.
I like to use both.

Mark Hooks
1967 OTS>


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mark E Hooks wrote:

Item 3 : There is a difference between airflow meters (such as Unisyn)
and Colortune. Colortune is
for setting the air fuel mixture. Airflow meters are for balancing the
airflow between the three carbs at idle.
I like to use both.

I agree. I have both the Gunson colortune, which is a sparkplug device
that lets you see the color of the flame in the cylinders, and a
Uni-Syn, which allows you to balance the air flow between carburettors
so that they are all sucking the same amount of air.

What I do is use the Colortune to get the mixture just to the point
where the flame color changes from yellow (rich), to a “bunsen blue”
color, approximately stoichiometric. Then I use the Unisyn to adjust
the linkages between the carburettors so that they are balanced at about
1000 rpm. Then I set the idle screws for the proper idle and again use
the Uni-Syn to balance the air flow. (Most SU type carburettors use the
idle screws to adjust the height of the slide piston, not the mixture).

The Uni-Syn that I have is ancient. I bought it in 1968 when I had my
first E-Type. Seems to me it was about $10 then. I’ve used it on
motorcycles when I did that for a living, and my own Jaguar and Datsuns.
It’s great for anything with multiple carbs that need balancing.______________________________________
George Cohn http://www.xke-lovers.com
1970 S2 OTS - Tucson, Arizona USA

Mark,

My thoughts below in CAPITALS

Dennis 69 OTS

Mark Hicks wrote:

O.K., let’s get some good tech discussions going. I’m getting bored and
Tony Vicarage has chosen to ignore me and isn’t answering any of my
questions, so here are somethings to chew on.

1 - The Jaguar specs say that the ideal timing (for my 3.8 SI)is
10degrees BTC. I was recently speaking with someone that strongly
recommended 5 degrees BTC but no more. Retarding and going up to
10degrees After top-dead center is fine but advancing beyond 10degrees
BTC is very bad for the car. Any conjecture?

I ADVANCE THE TIMING AS FAR AHEAD AS POSSIBLE TO GET BEST POWER. I DON’T
USE A TIMING LIGHT BUT JUST TURN THE DISTRIBUTOR CLOCKWISE AND TEST
DRIVE THE CAR. IF THERE IS PINGING WITH FOOT TO THE FLOOR I BACK IT OFF
UNTIL THE PINGING STOPS AS PRE-IGNITION IS BAD FOR THE ENGINE. SINCE
TIMING FOR MAXIMUM POWER IS NOT MAXIMUM GAS MILEAGE, I SUSPECT THAT
JAGUAR SET THE 10 DEGREES BTDC AS A COMPROMISE BETWEEN POWER AND ECONOMY

2 - I recently adjusted the mix in the carbs since one carb was running
obviously lean. The same friend went pale when he heard that I had been
running a lean. He said to always run a little rich with these cars
which might make you loose a little power but running lean is very, very
bad for the engine. My understanding was that running lean was not good
because it would just burn up the valves and plugs quicker and cause the
engine to run a little hot, but not death to an engine. Any conjecture?

TO ME A “LITTLE” LEAN IS NOT A BIG PROBLEM BUT JUST A HOTTER ENGINE. A
LITTLE RICH WOULD SEEM TO BE A WASTE OF GAS. KEEP IN MIND THE SINCE THE
SU THEORY IS THAT SETUP AT THE IDLE SETS THE MIX PERFECTLY THROUGHOUT
THE ENGINE SPEED RANGE, IF YOU HAVE LEAKING THROTLLE SPINDLES, THIS WILL
DISTORT THE PICTURE AND CAUSE YOU TO COMPENSATE FOR THE AIR LEAKED IN BY
RICHENING THE MIXTURE AT THE IDLE WHICH WILL UNNECCESSARILY RICHEN
THROUGHOUT THE RANGE.

3 - My friend also totally disgarded the idea of using an air-flow meter
(like Colortunes). He feels that they are entirely inaccurate with
E-Types. I must admit, I have one and have used it on my Austin-Healey
with only modest success, but never found them to really work on the
E-Type. Any conjecture?

I HAVE NEVER USED COLOURTUNE. I USED TO HAVE A $300 SEARS EXHAUST METER
THAT CALCULATED THE AIR/FUEL RATIO. IT CLIPS TO THE BATTERY AND HAS A
PROBE FOR THE EXHAUST PIPE SO YOU CAN DRIVE AROUND AND CHECK THE MIXTURE
AT VARIOUS THROTTLE OPENINGS. I WISH I STILL HAD IT!>

Regards,
Mark Hicks
'64 OTS, '66 2+2, '68 AH

Bounced. Forwarded to list. Check out the link he provides. A lot of
good info there even if the guy doesn’t know how to use a spell checker!---------------------------------------------------------------------
Date: Sat, 29 Aug 1998 22:40:15 -0700 (PDT)
From: Ron httpd@graphic1.com
To: e-type@jag-lovers.org
Subject: Re: [E-Type] Timing

Here is an old article about a Colortune Dyno
http://www.niksula.cs.hut.fi/~mdobruck/siililand/mini/diy/10/dyno.htm

Zapple

On Sat, 29 Aug 1998, George Cohn wrote:

mark E Hooks wrote:

Item 3 : There is a difference between airflow meters (such as Unisyn)
and Colortune. Colortune is
for setting the air fuel mixture. Airflow meters are for balancing the
airflow between the three carbs at idle.
I like to use both.

I agree. I have both the Gunson colortune, which is a sparkplug device
----snip----

Dennis,

IT CLIPS TO THE BATTERY AND HAS A PROBE FOR THE EXHAUST PIPE
SO YOU CAN DRIVE AROUND AND CHECK THE MIXTURE
AT VARIOUS THROTTLE OPENINGS. I WISH I STILL HAD IT!

Hmmm. A probe up the exhause pipe. Different stokes. :wink:

Regards,
Mark Hicks

Mark Hicks wrote:

O.K., let’s get some good tech discussions going. I’m getting bored and
Tony Vicarage has chosen to ignore me and isn’t answering any of my
questions, so here are somethings to chew on.

Now, Mark … Your comments are unwarrented and I suggest an apology is in
order… I have for the last few days been off the list attending to my
Mother who is dying in NY … perhaps her comfort is a little more
important than keeping up with the email…

After top-dead center is fine but advancing beyond 10degrees
BTC is very bad for the car.

We run our cars at 8-10 degress tdc at idle… However, that isnot the way to
do it… we start ata 26 to 28 degrees advance at 3/4k and work down…

2 - I recently adjusted the mix in the carbs since one carb was running
obviously lean. The same friend went pale when he heard that I had been
running a lean. He said to always run a little rich with these cars
which might make you loose a little power but running lean is very, very
bad for the engine. My understanding was that running lean was not good
because it would just burn up the valves and plugs quicker and cause the
engine to run a little hot, but not death to an engine.

Nothing wrong with a tad lean as it effects your idle… too rich and you
foul your plugs…tony

VICARAGE JAGUAR… Specialist Jaguar Restoration
Anthony Parkinson - Owner
USA/uk/Netherlands
Florida Tel 1 305 866 9511
fax 1 305 866 5738
Web Site: http://www.jagweb.com/vicarage Email: @Anthony_Parkinson

Mark Hicks wrote:

…I’m getting bored and Tony Vicarage has chosen to ignore me and isn’t answering any of my questions…

I’m getting bored and Mark H (and George C actually) has chosen to
ignore me. So, a question for you other listers. Just how quiet is the
gearbox on my '68 supposed to be. It’s been rebuilt but there’s still a
noticeable difference in the noise level if I depress the clutch (gears
stop spinning and everything is much quieter). The box works fine. Is
this “normal.” I know the earlier gearboxes were noisy but I thought
these later boxes were supposed to be quiet. Comments anyone??

Les.

Les, the noise you hear is the (ball) bearing on the first motion shaft,
the (small roller) bearing between the first motion shaft and the
mainshaft, and the two (roller) bearings on the layshaft. Were all of
these replaced?

Dennis 69 OTS-W

Les Halls wrote:>

Mark Hicks wrote:

…I’m getting bored and Tony Vicarage has chosen to ignore me and isn’t answering any of my questions…

I’m getting bored and Mark H (and George C actually) has chosen to
ignore me. So, a question for you other listers. Just how quiet is the
gearbox on my '68 supposed to be. It’s been rebuilt but there’s still a
noticeable difference in the noise level if I depress the clutch (gears
stop spinning and everything is much quieter). The box works fine. Is
this “normal.” I know the earlier gearboxes were noisy but I thought
these later boxes were supposed to be quiet. Comments anyone??

Les.

Don’t know Dennis. I know all the synchsro’ were replaced as well as a
host of roller bearings. I also know that the bearing and seal on the
input shaft were renewed. I’m probably just too critical about the
noise, nevertheless it does bug me. I’ll check out the other bearings
with the guy that did it for me.

Thanks …Les.

dkmacm@bc.sympatico.ca wrote:>

Les, the noise you hear is the (ball) bearing on the first motion shaft,
the (small roller) bearing between the first motion shaft and the
mainshaft, and the two (roller) bearings on the layshaft. Were all of
these replaced?

where are the timing marks for the 1970 xke s2 4.2?–
Robin 1970 XKE Red/Black 1R13616
Sacramento, CA, United States
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In reply to a message from Tobar sent Sat 31 Dec 2011:

On the crank pulley with a pointer visable from underneath at the
bottom of the engine.–
larry 71 sII
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