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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Mark. III Camies in `53 Shadow - What is right timing?
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<blockquote data-quote="timetraveller" data-source="post: 23713" data-attributes="member: 456"><p>Has anyone ever measured quieting ramps on a Mk III cam? The only Mk III cam I have ever measured up properly was a brand new one lent to me by Colin Jenner. It had just been manufactured by Gary Robinson and it timed up perfectly so I have no reason to think that the cam was in any way defective. There was nothing that could be considered quieting ramps on either the start or end of either of the lift profiles and calculating valve velocity and acceleration also did not show any difference from a Mk I. I have been told, but whether it is correct or just another Vincent myth, that the way in which the quieting ramps were produced was to grind the base circle 15 thou undersized and then to blend the new base circle into the original lift profiles over 20 degrees at the start and end of each cam lobe. Remember that this might be myth but if it is correct then it would not have been a quieting ramp and it would have been an incompetent modification. A proper quieting ramp would have had a slow lead in on the acceleration curve and it was just not there. If anyone has another Mk III cam which they think has a quieting ramp I would be happy to do the measurements again but the one example already measured did not have detectable ramps.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 23713, member: 456"] Has anyone ever measured quieting ramps on a Mk III cam? The only Mk III cam I have ever measured up properly was a brand new one lent to me by Colin Jenner. It had just been manufactured by Gary Robinson and it timed up perfectly so I have no reason to think that the cam was in any way defective. There was nothing that could be considered quieting ramps on either the start or end of either of the lift profiles and calculating valve velocity and acceleration also did not show any difference from a Mk I. I have been told, but whether it is correct or just another Vincent myth, that the way in which the quieting ramps were produced was to grind the base circle 15 thou undersized and then to blend the new base circle into the original lift profiles over 20 degrees at the start and end of each cam lobe. Remember that this might be myth but if it is correct then it would not have been a quieting ramp and it would have been an incompetent modification. A proper quieting ramp would have had a slow lead in on the acceleration curve and it was just not there. If anyone has another Mk III cam which they think has a quieting ramp I would be happy to do the measurements again but the one example already measured did not have detectable ramps. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Mark. III Camies in `53 Shadow - What is right timing?
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