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The ported vacuum takeoff is located ahead of the throttle butterflies so t=
hey are separated from manifold vacuum when the butterflies are closed. tha=
t means the vacuum advance comes into play when the throttle is opened and =
not at idle. Taking the signal from the manifold would mean the advance wou=
ld occur when the throttle is closed, which is the opposite of what the eng=
ine needs.
Bill Lawrence
________________________________
From: Healeys <healeys-bounces@autox.team.net> on behalf of Roger Grace <ro=
ggrace@telus.net>
Sent: Sunday, October 16, 2016 6:29 PM
To: Healey List
Subject: [Healeys] 123 Tune - timing settings
I recently installed a 123 Tune distributor on my BJ8, replacing a Pertroni=
x - mainly for ease of adjustments, repeatability, and to eliminate the mec=
hanical weights springs and vacuum advance; and not be constrained by the m=
echanical limits of the Lucas/Pertronix; a crank fired system was appealing=
but too much hassle to fit the toothed wheel !
Works OK - now after realising you have to be ultra diligent about taking u=
p the rotor drive freeplay before closing the cap.
Timing curves are set via a USB connection to a PC.
Checked with a timing light and the advance you set is what you get at the =
crank.
Hoping some other listers have installed a 123 Tune and would share the set=
tings/curves that have worked best for them on AH 3000 engines and not bein=
g constrained by mechanical advance. Also vacuum settings that have worked.
My manual gives 10 deg. static advance and 15 deg strobe at 600 RPM then 34=
-38 deg at 6400 RPM.
I used max of 35 deg at 6400 RPM
When I use these settings the timing was too retarded.
Checked with a vacuum gauge that was very jittery at 700 RPM and way down a=
t about 7-10 ins
To get a sensible vacuum reading (18ins) have to use around 22 deg at 600 R=
PM.
Did some road testing - the 123 software has a nice RPM stopwatch feature.
Around 22 deg seems to give best results. Went from 1200 RPM to 2800 RPM in=
4th and 3rd gears. Interesting - reducing advance to 17 deg made a big dif=
ference - lot worse. Use 94 octane Chevron and no pinging. Believe it is a =
standard cam. Only mod I have is a Maniflow exhaust header. Compression is=
OK at 155 psi ave.
So why are these advance setting so different to what the manual gives for =
the Lucas 25D ?
(I find some of the manual advance data to be confusing particularly the de=
celerating and vacuum settings)
Unfortunately didn't take a note of the settings I used before I made the d=
istributor change as had just set it "by ear".
Also wonder if anyone has tried manifold vacuum for advance instead of the =
ported take off ? With the flexibility of the 123 it sort of makes sense to=
deviate from the standard settings.
rg
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<p>The ported vacuum takeoff is located ahead of the throttle butterflies s=
o they are separated from manifold vacuum when the butterflies are closed. =
that means the vacuum advance comes into play when the throttle is opened a=
nd not at idle. Taking the signal
from the manifold would mean the advance would occur when the throttl=
e is closed, which is the opposite of what the engine needs.</p>
<p><br>
</p>
<p>Bill Lawrence</p>
<br>
<br>
<div style=3D"color: rgb(0, 0, 0);">
<hr tabindex=3D"-1" style=3D"display:inline-block; width:98%">
<div id=3D"divRplyFwdMsg" dir=3D"ltr"><font face=3D"Calibri, sans-serif" co=
lor=3D"#000000" style=3D"font-size:11pt"><b>From:</b> Healeys <healeys-b=
ounces@autox.team.net> on behalf of Roger Grace <roggrace@telus.net&g=
t;<br>
<b>Sent:</b> Sunday, October 16, 2016 6:29 PM<br>
<b>To:</b> Healey List<br>
<b>Subject:</b> [Healeys] 123 Tune - timing settings</font>
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line">
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<div style=3D"font-size:12pt; font-family:'Comic Sans MS'; color:#000000">
<div style=3D"word-wrap:break-word">I recently installed a 123 Tune distrib=
utor on my BJ8, replacing a Pertronix – mainly for ease of adjustment=
s, repeatability, and to eliminate the mechanical weights springs and vacuu=
m advance; and not be constrained by the
mechanical limits of the Lucas/Pertronix; a crank fired system was appeali=
ng but too much hassle to fit the toothed wheel !</div>
<div style=3D"word-wrap:break-word"> </div>
<div style=3D"word-wrap:break-word">Works OK - now after realising you have=
to be ultra diligent about taking up the rotor drive freeplay before closi=
ng the cap.</div>
<div style=3D"word-wrap:break-word">Timing curves are set via a USB connect=
ion to a PC.</div>
<div style=3D"word-wrap:break-word">Checked with a timing light and the adv=
ance you set is what you get at the crank.</div>
<div style=3D"word-wrap:break-word"> </div>
<div style=3D"word-wrap:break-word">Hoping some other listers have installe=
d a 123 Tune and would share the settings/curves that have worked best for =
them on AH 3000 engines and not being constrained by mechanical advance. Al=
so vacuum settings that have worked.</div>
<div style=3D"word-wrap:break-word"> </div>
<div style=3D"word-wrap:break-word">My manual gives 10 deg. static advance =
and 15 deg strobe at 600 RPM then 34-38 deg at 6400 RPM.</div>
<div style=3D"word-wrap:break-word">I used max of 35 deg at 6400 RPM</div>
<div style=3D"word-wrap:break-word">When I use these settings the timing wa=
s too retarded.</div>
<div style=3D"word-wrap:break-word">Checked with a vacuum gauge that was ve=
ry jittery at 700 RPM and way down at about 7-10 ins</div>
<div style=3D"word-wrap:break-word"> </div>
<div style=3D"word-wrap:break-word">To get a sensible vacuum reading (18ins=
) have to use around 22 deg at 600 RPM.
</div>
<div style=3D"word-wrap:break-word">Did some road testing – the 123 s=
oftware has a nice RPM stopwatch feature.</div>
<div style=3D"word-wrap:break-word">Around 22 deg seems to give best result=
s. Went from 1200 RPM to 2800 RPM in 4th and 3rd gears. Interesting - reduc=
ing advance to 17 deg made a big difference – lot worse. Use 94 octan=
e Chevron and no pinging. Believe it is
a standard cam. Only mod I have is a Maniflow exhaust header. Compre=
ssion is OK at 155 psi ave.</div>
<div style=3D"word-wrap:break-word"> </div>
<div style=3D"word-wrap:break-word">So why are these advance setting so dif=
ferent to what the manual gives for the Lucas 25D ?</div>
<div style=3D"word-wrap:break-word">(I find some of the manual advance data=
to be confusing particularly the decelerating and vacuum settings)
</div>
<div style=3D"word-wrap:break-word">Unfortunately didn’t take a note =
of the settings I used before I made the distributor change as had just set=
it “by ear”.</div>
<div style=3D"word-wrap:break-word"> </div>
<div style=3D"word-wrap:break-word">Also wonder if anyone has tried manifol=
d vacuum for advance instead of the ported take off ? With the flexibility =
of the 123 it sort of makes sense to deviate from the standard settings.</d=
iv>
<div style=3D"word-wrap:break-word"> </div>
<div style=3D"word-wrap:break-word">rg </div>
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