Re: [Healeys] Healey 100-4 timing

[Kees Oudesluijs <coudesluijs@chello.nl>]

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The maximum advantage should be limited to prevent damage to the big end 
bearings. In general, depending on the engine, this is around 32° to 35° 
/*total*/ advance. The distributor advance system with the weights and 
springs is limited to about 17°, the vacuüm advance or retard (depending 
on engine) may produce another 5° or so advance or retardation. This 
means that when the ignition of an engine with a vacuum advance system 
is set at say 10° static, the maximum advance is a safe 32° at anything 
over about 2500rpm.

Kees Oudesluijs



Op 3-11-2018 om 03:05 schreef Michael Salter:
> Thanks for your input on ignition timing Michael.
> I have always found the factory specs to be a little confusing.
> They state 6 degrees BTDC as the timing (which I presume to be 
> "static") and then state that the distributor produces 16 - 18 degrees 
> at 2000 RPM (distributor speed) which I figure to be 32 -36 degrees at 
> 4000 engine RPM.
> I interpret that to produce 6 + 34 (2 x 17) degrees BTDC at 4000 
> engine RPM for a total of 40 degrees which sounds like an awful lot.
> My engine does not sound at all happy with 40 degrees even with 110 
> octane!!
> I'm wondering if I have been over thinking this process and the stated 
> advance is meant to be "at idle" with the vacuum connected (not normal 
> practice as far as I was taught) which would add 6 degrees of vacuum 
> advance which would vanish at full throttle producing a net of 34 
> degrees over 4000 at full throttle.
> I have been setting the timing to 32 degrees BTDC with the vacuum 
> disconnected at 4000 RPM and the engine runs fey well and very cool, 
> in fact too cool without a 180 degree thermostat.
> I am running 8.3:1 compressions with an M cam.
>
> M
>
>
> On Fri, Nov 2, 2018 at 9:16 PM Michael Oritt <michael.oritt@gmail.com 
>
>     Wayne--
>
>     Exactly right--it is total advance that matters and I arrived at
>     that number by gradually increasing advance and seeing the effect
>     upon water temperature at speed and under full load.  Anything
>     more and the car would begin to overheat. A bit too much less
>     advance and performance fell off.
>
>     BTW I am running a DW "fast street" cam and tubular header and a
>     Mallory non-vacuum advance distributor fired with their Unilite
>     module.  I too have a Smitty's five-speed and the Toyota box, 180
>     XAS's and 3.54 diff set give me about 72-73 mph at 3K rpm's indicated
>
>     Best--Michael Oritt
>
>     On Fri, Nov 2, 2018 at 6:03 PM Wayne Schultz <waschu2@gmail.com
>
>         Thanks to Michael and others I am going to stick with 34 - 35
>         degrees total advance for now. What, I think this means, is
>         that the advance at idle is secondary and not as important as
>         total advance. Cruising with the the Toyota five speed or the
>         original overdrive on the highway is right in the 3K RPM range
>         so I think this the perfect RPM to limit total advance. I
>         might make a run to my local airport and buy some 100LL fuel.
>         I have worked in aviation since 1967 so I have a few friendsð???
>
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    <p>The maximum advantage should be limited to prevent damage to the
      big end bearings. In general, depending on the engine, this is
      around 32° to 35° <i><b>total</b></i> advance. The distributor
      advance system with the weights and springs is limited to about
      17°, the vacuüm advance or retard (depending on engine) may
      produce another 5° or so advance or retardation. This means that
      when the ignition of an engine with a vacuum advance system is set
      at say 10° static, the maximum advance is a safe 32° at anything
      over about 2500rpm.</p>
    <p>Kees Oudesluijs</p>
    <p><br>
    </p>
    <p><br>
    </p>
    <div class="moz-cite-prefix">Op 3-11-2018 om 03:05 schreef Michael
      Salter:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAB3i7LLxqZmUttWxBBuU6FkwBqKhTehbOvzTbk4n0fTa1w1Qvg@mail.gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <div dir="ltr">
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">Thanks for your input on
          ignition timing Michael. <br>
        </div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">I have always found the factory
          specs to be a little confusing.</div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">They state 6 degrees BTDC as
          the timing (which I presume to be "static") and then state
          that the distributor produces 16 - 18 degrees at 2000 RPMÂ 
          (distributor speed) which I figure to be 32 -36 degrees at
          4000 engine RPM.</div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">I interpret that to produce 6 +
          34 (2 x 17) degrees BTDC at 4000 engine RPM for a total of 40
          degrees which sounds like an awful lot.</div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">My engine does not sound at all
          happy with 40 degrees even with 110 octane!!</div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">I'm wondering if I have been
          over thinking this process and the stated advance is meant to
          be "at idle" with the vacuum connected (not normal practice as
          far as I was taught) which would add 6 degrees of vacuum
          advance which would vanish at full throttle producing a net of
          34 degrees over 4000 at full throttle.<br>
        </div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">I have been setting the timing
          to 32 degrees BTDC with the vacuum disconnected at 4000 RPM
          and the engine runs fey well and very cool, in fact too cool
          without a 180 degree thermostat.<br>
        </div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">I am running 8.3:1 compressions
          with an M cam.</div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small"><br>
        </div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small">M<br>
        </div>
        <div class="gmail_default" style="font-family:comic sans
          ms,sans-serif;font-size:small"> <br>
        </div>
      </div>
      <br>
      <div class="gmail_quote">
        <div dir="ltr">On Fri, Nov 2, 2018 at 9:16 PM Michael Oritt &lt;<a
            href="mailto:michael.oritt@gmail.com"; 
moz-do-not-send="true">michael.oritt@gmail.com</a>&gt;
          wrote:<br>
        </div>
        <blockquote class="gmail_quote" style="margin:0 0 0
          .8ex;border-left:1px #ccc solid;padding-left:1ex">
          <div dir="ltr">
            <div class="gmail_default" style="color:#3333ff">Wayne--</div>
            <div class="gmail_default" style="color:#3333ff"><br>
            </div>
            <div class="gmail_default" style="color:#3333ff">Exactly
              right--it is total advance that matters and I arrived at
              that number by gradually increasing advance and seeing the
              effect upon water temperature at speed and under full
              load.  Anything more and the car would begin to overheat. 
              A bit too much less advance and performance fell off.  </div>
            <div class="gmail_default" style="color:#3333ff"><br>
            </div>
            <div class="gmail_default" style="color:#3333ff">BTW I am
              running a DW "fast street" cam and tubular header and a
              Mallory non-vacuum advance distributor fired with their
              Unilite module.  I too have a Smitty's five-speed and the
              Toyota box, 180 XAS's and 3.54 diff set give me about
              72-73 mph at 3K rpm's indicated</div>
            <div class="gmail_default" style="color:#3333ff"><br>
            </div>
            <div class="gmail_default" style="color:#3333ff">Best--Michael
              Oritt</div>
          </div>
          <br>
          <div class="gmail_quote">
            <div dir="ltr">On Fri, Nov 2, 2018 at 6:03 PM Wayne Schultz
              &lt;<a href="mailto:waschu2@gmail.com"; target="_blank"
                moz-do-not-send="true">waschu2@gmail.com</a>&gt; wrote:<br>
            </div>
            <blockquote class="gmail_quote" style="margin:0 0 0
              .8ex;border-left:1px #ccc solid;padding-left:1ex">
              <div dir="ltr">Thanks to Michael and others I am going to
                stick with 34 - 35 degrees total advance for now. What,
                I think this means, is that the advance at idle is
                secondary and not as important as total advance.
                Cruising with the the Toyota five speed or the original
                overdrive on the highway is right in the 3K RPM range so
                I think this the perfect RPM to limit total advance. I
                might make a run to my local airport and buy some 100LL
                fuel. I have worked in aviation since 1967 so I have a
                few friendsð??? 
                <div><br>
                </div>
              </div>
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