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General Chat (Vincent Related)
alscomet with unmarked timing gears
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<blockquote data-quote="timetraveller" data-source="post: 1546" data-attributes="member: 456"><p>OK Guys, do it how you want BUT is the cam a Mk I or a Mk II or even one of these 105 degree ones which are about now. (The Mk IIIs which I have measured no more have quieting ramps than I do.) I know that it is time consuming but I still recommend plotting out the whole lift profile of both inlet and exhaust valves and then plotting the numbers up either by hand or in a spread sheet. Many old Vincent cams have a serious flat either at the start or end of the lift and this makes timing difficult. With the full information one can make the best of a compromise on the timing if the cams are not what you think or are poor quality. It takes me about one hour on my own to take a measurement every ten degrees of engine rotation of both lobes on one cam. Nowadays I then always put those numbers into EXEL. I also have set the spread sheet up so that it shows the velocity and acceleration of both cams. That can be rather depressing. I did this years ago for some specials that (an engineer) had made for Roy Robertson with an extra 1 mm of lift. The acceleration was a factor of seven times greater than what is normally allowed and resulted in the valve heads falling off and wrecking the engine. If anyone wants a copy of the spread sheet then I can send them a blank version for them to play about with.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 1546, member: 456"] OK Guys, do it how you want BUT is the cam a Mk I or a Mk II or even one of these 105 degree ones which are about now. (The Mk IIIs which I have measured no more have quieting ramps than I do.) I know that it is time consuming but I still recommend plotting out the whole lift profile of both inlet and exhaust valves and then plotting the numbers up either by hand or in a spread sheet. Many old Vincent cams have a serious flat either at the start or end of the lift and this makes timing difficult. With the full information one can make the best of a compromise on the timing if the cams are not what you think or are poor quality. It takes me about one hour on my own to take a measurement every ten degrees of engine rotation of both lobes on one cam. Nowadays I then always put those numbers into EXEL. I also have set the spread sheet up so that it shows the velocity and acceleration of both cams. That can be rather depressing. I did this years ago for some specials that (an engineer) had made for Roy Robertson with an extra 1 mm of lift. The acceleration was a factor of seven times greater than what is normally allowed and resulted in the valve heads falling off and wrecking the engine. If anyone wants a copy of the spread sheet then I can send them a blank version for them to play about with. [/QUOTE]
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General Chat (Vincent Related)
alscomet with unmarked timing gears
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