Camshaft consumers have been getting more sophisticated over the years. Engine builders and even some individuals are checking their camshafts with a computerized cam profiler before installing them. Those not using computers are checking their camshafts with a dial indicator and degree wheel. This has caused the camshaft grinder to profile each camshaft on his own cam profiler before sending it to his customer. The camshaft grinder uses the actual data retrieved to create the camshaft specification card. This prevents having to explain later why the camshaft specifications do not agree with the card.
Years ago when computer designed cam profiles were becoming common, a model lobe was created from the design data in a milling machine and a cam profile master plate was then created from the model in the camshaft grinding machine. This was before CNC machines were used to make the master plate from the design data. The master plate is used in manually operated camshaft grinding machines to make the camshaft. The most popular machines are the Van Norman and Berco camshaft grinders. There are many of these machines used today to make camshafts. The machine uses a follow wheel to trace the master plate shape onto the camshaft. There are many videos on the internet showing the operation of these machines. Check them out if you are not familiar with how a camshaft grinding machine works.
Between the cam profile design, the making of the model lobe, the making of the master plate, and the making of the camshaft, many errors are accumulated. I am not sure but I may have just let out a big secret. I always say, there are three different cam profiles for each design. The original design (1), the actual lobe on the camshaft (2), and the profile that is created in a running engine (3). Obviously, you want all three to be the same, but in reality, they are not. Today’s technology is allowing them to become closer. Making master plates directly from the profile design data using CNC machines has removed many of the errors experienced years ago. A well maintained Berco camshaft grinder and CNC produced masters, along with a skilled operator, will produce a wonderful camshaft.
Back to the years ago. There was usually a big difference between the original cam profile design and the finished camshaft lobe. A decrease of around 2-3 degrees in duration and 0.003 in lift were common discrepancies. This was from the major camshaft grinders of the time. If the camshaft grinder created the specification card from the original design, and most did, the actual camshaft specifications did not mach. Most people did not analyze their camshaft at the time and the small differences in specifications were usually accepted. It was just considered the normal tolerance. Today, the consumer expects to receive a camshaft with all the lobes matching the specifications exactly. Unless the camshafts are being ground on CNC machines, it is very hard to deliver that kind of quality. Profiling the camshaft and using that data for the specifications, is the only way to make them match and please the customer.