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<div class="moz-cite-prefix">As you do not have rockers in a twin
cam set up you can allow higher RPM without the need of stiffer
valve springs. It is also easier to play around with the valve
timing as you can set up inlet and exhaust cam separately. You can
also create a better shape of the combusting chamber and a
multivalve set up, i.e. better breathing.<br>
This is shown by many of the racing engines already developped in
early motor history and also in most powerful modern engines with
a high specific output.<br>
Kees Oudesluijs.<br>
<br>
<br>
<br>
Op 9-7-2017 om 3:28 schreef John Rowe:<br>
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<p class="MsoNormal"><span>Not sure of the advantages, by my
Alfa Romeo GTV is definitely a nicer engine than either of
the Healeys or any single cam Japanese car I’ve driven</span></p>
<p class="MsoNormal"><span>John Rowe</span></p>
<p class="MsoNormal"><span>Qld Australia</span></p>
<p class="MsoNormal"><span> </span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span
lang="EN-US"> Healeys
[<a class="moz-txt-link-freetext" href="mailto:healeys-bounces@autox.team.net">mailto:healeys-bounces@autox.team.net</a>] <b>On Behalf Of
</b>Bob Spidell<br>
<b>Sent:</b> Sunday, 9 July 2017 6:00 AM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:healeys@autox.team.net">healeys@autox.team.net</a><br>
<b>Subject:</b> [Healeys] Cams - Was: Re: Vernier timing
gears</span></p>
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<p class="MsoNormal"> </p>
<p>I never understood the advantage of 'twin' cams (assuming two
cams per bank of cylinders, one for intake and one for
exhaust). Can't the same results come from lobe profiles;
i.e. one profile for intake and one for exhaust, on the same
cam? All the twin cam setups I've seen have both cams driven
by the same belt, so timing will be the same for both cams.
Is this idea just to have less 'load' for each cam?</p>
<p> </p>
<p>What does make sense to me is variable cam timing. My
Mustang accelerates smoothly and seamlessly, but on coasting
deceleration there is a noticeable 'bump' down in RPM around
1,800-2,000 RPM as the ECU changes--advances?--the cam timing,
but it only has one cam per bank. I know the Honda VTEC
engines have a third lobe, that only comes into play at higher
speeds (thanks Edd!).</p>
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<p class="MsoNormal">On 7/8/2017 12:43 PM, David Porter wrote:</p>
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<p>I guess my point in generating some "traffic" is best
expressed by Mr. Lawrence. With a single cam acting on the
valve timing, one can set it close to factory or deviate a
couple degrees advanced or retarded for low end torque or
high rpm breathing. It is still a trade off versus a twin
cam head where both can be affected and gains can be easily
(?) obtained for both instances he states. Not too sure we
all have easy access to a dyno. These old long stroke 6/4's
were designed for grunt. That would be the wise choice. They
don't like to be spun up much, then the Welch crank would be
necessary. $$ dave</p>
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<p class="MsoNormal">On 7/7/2017 7:16 PM, WILLIAM B LAWRENCE
wrote:</p>
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<p><span>According to Iskendarian You can optimize cam
timing either to provide a boost in low end torque
by advancing the timing by up to 8 degrees or in
high end power by retarding it a similar amount. </span></p>
<p><span> </span></p>
<p><span>Since I am looking for a low end boost and will
rarely exceed 3500 on the road I set mine 4 degrees
in advance.</span></p>
<p><span> </span></p>
<p><span>Waiting to see how it works out...</span></p>
<p><span> </span></p>
<p><span>Bill Lawrence</span></p>
<p><span>BN1 #554</span></p>
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