Advance/Retard cam timing and Dyno 2003 sims

[gonridnu]

It would be helpful to know actual numbers below 2000 RPM. If you are simply moving the RPM higher that peak torque occurs at, which retarding the cam does, you may be realizing a small increase based on the time component of the torque equation. Without the numbers below 2k RPM we cannot tell when peak torque is occuring.

I have only used 3 simulators of varying complexity. As piston speed and rod angle relate to valve opening points, it would seem to me the more data points you can enter the more reliable the result. One of the simulators I used allowed for rod length and multiple lift points on the camshaft. By including that info you can see the "area under the curve" of the cam lobe as well as piston position and speed relative to valve events. It is important they have an actual rocker ratio component and cam lobe lifts rather than being based off basic lift and duration numbers. These all contribute to a more accurate picture of the valve opening event and timing.

Cam selection is in large part based on intended operating RPM. Advancing or retarding alters peak torque as direct relationship to the intake valve opening point in the cycle. It can also be utilized to alter piston to valve clearance, as well as have a minor effect on compression. The best advice I can offer is to look for a camshaft that operates at your intended RPM with your compression. If you find it necessary to adjust that RPM range for whatever reason then retard or advance it accordingly. Personally, I tend to put a lot of cams in "straight up" unless there is a specific reason for not doing so, including intended operating RPM.

[gonridnu]

And the Cloyes (or other brand) crank gear changes your valve events by +/- 4 degrees of crankshaft rotation. When you degree your cam you are measuring linear lift at the lifter relative to crankshaft rotational degrees. Even when you change it at the cam using a hex adjust, belt drive, or offset bushings you are working in units of crankshaft degrees of rotation.