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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
I need a drawing of ET84, exhaust nut
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<blockquote data-quote="davidd" data-source="post: 34535" data-attributes="member: 1177"><p>John,</p><p></p><p>I think that you can do exactly what you want with the design that I used. I am not smart enough to be left on my own with exhaust design. I know that Terry's heads had an anti-reversion device in the form of a "D" shaped port. Carleton's flow testing showed that it did not work for the high-revs he wanted. One of the issues that Vincent owners face with high revving engines is that the available cams will not produce power over 6000 rpm. Once you produce a cam to go over that barrier, your mean gas velocity requirements usually limit you to an 1-3/4" pipe as the 2" pipes do not generate enough velocity to prevent some exhaust gas from flowing backwards (reversion).</p><p></p><p>As to the sonic requirements, namely, the negative pulses, it seems to me these are a good thing in moderation, pulling in the intake charge during overlap. Most of the lore says that a Vincent does not like a megaphone, but I think it is just the opposite. In fact, I think, in a crude way, the exhaust sees a two inch pipe as a megaphone of sorts. Coburn always ran a megaphone for max power in the 60's and 70's. Carleton always got max power with a megaphone and Lindsay Kyle is getting 45 HP plus from his Comet with an 1-34" pipe and a megaphone with a silencer. I think that there was just no money for development.</p><p></p><p>I think what you are doing is very interesting and am looking forward to your reports when it is running.</p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 34535, member: 1177"] John, I think that you can do exactly what you want with the design that I used. I am not smart enough to be left on my own with exhaust design. I know that Terry's heads had an anti-reversion device in the form of a "D" shaped port. Carleton's flow testing showed that it did not work for the high-revs he wanted. One of the issues that Vincent owners face with high revving engines is that the available cams will not produce power over 6000 rpm. Once you produce a cam to go over that barrier, your mean gas velocity requirements usually limit you to an 1-3/4" pipe as the 2" pipes do not generate enough velocity to prevent some exhaust gas from flowing backwards (reversion). As to the sonic requirements, namely, the negative pulses, it seems to me these are a good thing in moderation, pulling in the intake charge during overlap. Most of the lore says that a Vincent does not like a megaphone, but I think it is just the opposite. In fact, I think, in a crude way, the exhaust sees a two inch pipe as a megaphone of sorts. Coburn always ran a megaphone for max power in the 60's and 70's. Carleton always got max power with a megaphone and Lindsay Kyle is getting 45 HP plus from his Comet with an 1-34" pipe and a megaphone with a silencer. I think that there was just no money for development. I think what you are doing is very interesting and am looking forward to your reports when it is running. David [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
I need a drawing of ET84, exhaust nut
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