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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: 23781" data-attributes="member: 456"><p>OK Sebastian. One thing to remember is that the lift profiles have to be done on top of the valves and not just from the cams. The reason for this is that the followers are the lever type and give a variable ratio as the cams touch different positions along the base of the followers. If you really have access to some high tech equipment when you do it then you need a digital depth gauge and digital rotary encoder, both able to read out to a computer file. The figures can be put into a spread sheet and the lift profiles, velocity and acceleration curves can be made to appear at the same time. If you do not have access to this type of equipment the you will have to do it the slow way, which is what I do, and use a degree plate on the engine and take lift figures every ten degrees of engine rotation or more if you have the time and patience. If you want to get accurate acceleration curves then you need to have a degree plate that can be read off to better than one degree and a dial gauge able to be read to about one tenth of one thousandth of an inch (about two and a half microns in metric measurements). At home I use a rotary table to rotate the engine so that can be done accurately and it overcomes the problem of the engine trying to rotate under the pressure of the valve springs. If when you get round to it you need any help or advice on setting up the spread sheet just ask.</p><p>A week ago when doing Norman Lord's cams for his twin I did start off with what is called 'the rocking method' where one tries to judge equal lifts on the exhaust closing and the inlet opening at 4 to 6 degrees before top dead centre. I would be prepare to concede that I am not gifted at doing this but both cylinders needed the cams advance by about 15 degrees, one tooth on the cam pinion. Not near enough for me.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 23781, member: 456"] OK Sebastian. One thing to remember is that the lift profiles have to be done on top of the valves and not just from the cams. The reason for this is that the followers are the lever type and give a variable ratio as the cams touch different positions along the base of the followers. If you really have access to some high tech equipment when you do it then you need a digital depth gauge and digital rotary encoder, both able to read out to a computer file. The figures can be put into a spread sheet and the lift profiles, velocity and acceleration curves can be made to appear at the same time. If you do not have access to this type of equipment the you will have to do it the slow way, which is what I do, and use a degree plate on the engine and take lift figures every ten degrees of engine rotation or more if you have the time and patience. If you want to get accurate acceleration curves then you need to have a degree plate that can be read off to better than one degree and a dial gauge able to be read to about one tenth of one thousandth of an inch (about two and a half microns in metric measurements). At home I use a rotary table to rotate the engine so that can be done accurately and it overcomes the problem of the engine trying to rotate under the pressure of the valve springs. If when you get round to it you need any help or advice on setting up the spread sheet just ask. A week ago when doing Norman Lord's cams for his twin I did start off with what is called 'the rocking method' where one tries to judge equal lifts on the exhaust closing and the inlet opening at 4 to 6 degrees before top dead centre. I would be prepare to concede that I am not gifted at doing this but both cylinders needed the cams advance by about 15 degrees, one tooth on the cam pinion. Not near enough for me. [/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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