Here is the profile graph and the model milling lift table for a popular NASCAR Winston Cup lobe profile we designed in the 1980's. This would be "top secret" stuff at the time. This is considered an old design compared to the lobe designs of today. It is an asymmetrical flat tappet lobe with a rate designed for high RPM and endurance. It has easy ramps with a running lash of .012 for rocker ratios of 1.5 or 1.6. It was designed with our software program for the 0.874 diameter flat tappets and valve springs used at the time. A lobe profile design today would probably dwell the maximum velocity on the opening and closing sides of the lobe. Different ramp designs would probably also be used. Today's lobe design would have more area with the same duration numbers at .020 and .050 and the same lift. The duration numbers at .100, .200, and .300 would be larger. The larger area is the major difference between a new lobe design and an old lobe design. Lighter and stronger valve train components make it possible to design lobe profiles with faster rates and more area. Camshafts with larger journal diameters are also an advantage. It would be interesting to analyze the NASCAR camshaft lobes of the 1960's and 70's. You need to know where you've been to know where to go.

Profile available for the MS-DOS Reed program.

This is the conclusion and summary of the previous five lessons. We have created the opening ramp of the profile, the opening side of the profile, the closing side of the profile, and the closing ramp of the profile. We then put all four sections together and created the cam profile. In all reality a fairly easy process if you have a computer program that does the math for you. You have to admire the people that did this stuff before the assistance of a computer or even an electronic calculator.

Here is my unique example of what the tappet will experience during its travel up and down the lobe. You need to image that you are the tappet. You are going up one side of a hill and down the other side. You start off walking up the hill (opening ramp) at around a constant pace (velocity and acceleration). Like walking up the stairs. At some point your pace will start to increase. You are now running. You will reach maximum acceleration first and then maximum velocity. If you are a flat tappet the maximum velocity will be determined by your diameter. A roller tappet will limit your maximum acceleration. If you exceed either limit you will fall down, skin yourself up, and roll down the hill. Basically the tappet and the camshaft will be destroyed. If you are not destroyed, your pace will start to slow as you reach the top of the hill (maximum lift).

From this point you will travel down the other side of the hill. You will go through the same velocity and acceleration forces just in the opposite direction. You will reach maximum velocity first and then maximum acceleration. Eventually you will slow down and stop at the bottom of the hill (closing ramp). You can follow along by using the profile graph showing the velocity and acceleration curves.

Velocity, acceleration, and jerk can be confusing. An easy way to understand these forces is in your car. The velocity is the speed, the reading on the speedometer. Velocity is usually associated with acceleration. Acceleration is how quickly you get to that speed. Jerk is the forward and backward movement that you feel when speeding up and slowing down quickly. That "jerky" motion. It can be very annoying. It is also very annoying in lobe profile designs. A lot of jerk creates a lot of stress in the valve train just like in the car. All of these forces are easy to experience while driving your car (try it). You want all of these forces to be nice and smooth, not to harsh and not to soft, just right.

As I have said before, the software only does the math. It is up to the lobe designer to create a good profile design. As you better understand these forces and how they affect the lobe profile, the better your designs will be. Some other calculations you will need to do are the maximum velocity for the flat tappet diameter, radius of curvature of the lobe, valve closing velocity, base circle diameter of the lobe, pressure angle between the tappet and the lobe, duration at different tappet heights, valve lift, and valve lash.

All of this stuff is just math, physics, and numbers. No magic. As long as your lobe design doesn't tear-up something, consider it a good design. It may not make as much power as you would like but that's ok for now. It all just takes time. Hopefully you enjoyed these introductory lessons to the cam profile design process. Depending on the response to these lessons, I can go further into the design process using more examples with more detail. Let me know if you have any questions or suggestions or if you want to purchase the program. Good luck to everyone. Class dismissed.

If you read my website regularly, you will notice changes in wording along with other changes. I am always re-reading and looking at the website and making changes, hopefully to make things easier to follow and understand. Nothing drastic, usually just changes in the wording. It may help you to go back and read things over again. I have edited the cam design lessons many times already since they were first posted. I'm sure I will change them some more.

I read a lot for the purpose of learning something new. I may read the same thing over and over until I understand it. That is the purpose of "CAM TALK". You must read and comprehend the material in order to learn something. It's like watching the same movie or video many times and seeing something new each time. I think there is finally enough information on the website now for someone to understand cam profiles and actually design a lobe profile using the proper software. There are definitions, descriptions, and examples for all the terms used in cam profile design. There are actual numbers and range of numbers to use for various parameters. This is all information I have not seen anywhere else on the internet or in books. I share this information because it is not easily found. I remember being very frustrated trying to find this kind of information. It is still frustrating. Many people involved in this stuff seem to be hard to talk with and very hush, hush about sharing knowledge. They will only sell you their knowledge. You must buy their books or pay to go to their seminars.

Carefully read all of my posts, take notes. If there is something that you don't understand, ask me. I am not one of those people mentioned earlier. I am glad to share knowledge and help. I know there are not many people that are interested in this stuff but I am a good source of information for those that are. If you are someone who already knows all about this stuff, please contact me and introduce yourself.