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Discussion and questions related to the course How to Degree a Cam
Hi, I have some questions about the advertised duration. So this is the lift of the cam when valves are considered open and closed? Is this when valves are fully open or starting to open? In this case, is 0.006¨ but based on their knowledge are the valves fully open or starting to open? And the duration (the paragraph below), what exactly means "remove the influence of the opening and closing portions? When valves starting to open/close?
Adverised cam duration is the number in crank shaft rotation degrees when the valve is off its seat at specific height. This height can be different depending on the standard being used as some companies use 0.04 inch height, some use 0.05 inch...
majority of the time it is .05 on 95% of the cams on the shelf or by big suppliers
It depends on specific location. Abroad of USA most common lift is 1mm which is 0.04 inch...
"The openig and closing portions" may refer to the clearance (AKA take up or quietning ramps. With mechanical camshafts there is a small amount of clearance and to give a smoother initial opening, and closing transition, the camshafts have a sort of 'taper'before the main camshaft lift occurs. Without the ramps, or when there's too much clearance, the sudden take up can send sudden, high forces through the valve train and/or increase the chance of the valve bouncing on it's seat. You can hear this as the increased valve train noise when there're excessive valve clearances.