<html><body><div style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 10pt; color: #000000"><div>Without the possibility of computer ignition mapping, the most important thing is the maximum total advance. This can start from 3000rpm or higher, depending on the distributor springs.</div><div>2 degrees is already making a significant difference for horsepower. On a dyno one can find at what advance the engine is making the best power, but it is all important to find out if the power is not dropping after 20 or 30 seconds (detonation).</div><div>And the the circumstances on a race week-end can be different : if one is arriving at 30° during a dyno session, it is possible that only 28° is safe on a particular day. Total maximum advance can differ considerably (compression ratio,...).</div><div>I believe that a fresh engine tends to pre-ignition more easily because of glowing spots : protruding headgasket(wich should be avoided of course), sharp machining edges...In an older engine the surfaces of the combustion chambers will be smoother</div><div>Marcel</div><div><br></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><b>Van: </b>"fot" <fot@autox.team.net><br><b>Aan: </b>"fot" <fot@autox.team.net><br><b>Verzonden: </b>Vrijdag 19 maart 2021 23:53:55<br><b>Onderwerp: </b>Re: [Fot] Distributor centrifugal advance curve for race engine<br></div><div><br><style>/*<![CDATA[*/p.MsoNormal, li.MsoNormal, div.MsoNormal {
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/*]]>*/</style></div><div data-marker="__QUOTED_TEXT__"><p>When I had crank fire ignition I did test it on the dyno and
found that a slight retard as RPM's went up helped (at least
that's how I remember it - up to 34 / 35 at 3000 rpm but down to
32 at 6000). But with my more vintage points system, the advance
is "all in" at 3000 rpm. I just set to 30 degrees or 32 degrees
or if I'm feeling particularly lucky / brave / stupid 34 degrees
at max. Whatever it ends up at low rpm is where it ends up. When
racing I'm never under 3000 RPM anyway.</p>
<p>Regards, Tony<br>
</p>
<div class="moz-cite-prefix">On 3/19/2021 5:27 PM, timmmurphh--- via
Fot wrote:<br>
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<p class="MsoNormal">What advance curve are folks using in their
race engines? I have 87mm pistons, a Kastner G3 cam and about
a 12:1 compression ratio. I am using about 19 degrees advance
at idle (no centrifugal advance) and 30 degrees advance at
3000 RPM. I don’t know what I have at higher RPM’s because I
never looked. I’m currently doing an engine rebuild so I will
have to look what I’ve got at the higher RPM’s when I get the
engine running. I’m curious as to what others are using and if
anyone has done any testing on a dyno with different advance
curves.</p>
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<p class="MsoNormal">Thanks in advance for your input.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Tim Murphy</p>
<p class="MsoNormal">#317 BRG TR4</p>
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