Why are the Cams different in a Roller SR20. Why Can't I just throw Non Roller Cams in there?
You can throw a monkey in a gorilla suit in the Congo and he will live, but it doesn't mean he will function correctly. In other words, yes, now I understand that it has been done, a non roller camshaft has been installed in a roller rocker head. but it doesn't mean it is advisable. I have no clue what power it may or may not yield... but from a long discussion and a little thinking I know now that each cam (roller & non roller) has applications for each valve train's attributes. Let me explain what I found out from JWT:
The intake & exhaust valves are 3mm shorter in a roller rocker engine... then non roller SR20DE has a 40mm install height and different valve springs then roller. The RR has a 37mm install height. The center of bearings of the RR camshafts are all the same diameter as the conventional SR20, but lobes are very, very, very different. The rocker arms are different; the radius of contact is different, the distance from pivot point, the moment of inertia, the mass of the rocker, etc.
The initial point on which cam contacts the roller is different... by implementing a different cam into the wrong valve train one can incoherently advance or retard the cam motion... The phasing of it where it first touches the rocker arm is different. The Radius of curvature can make a great deal in the difference in contact stresses as well. It can produce a valve motion that it wasn't design for. In theory it can mess up harmonics of the valve train and at a certain rpm it may excite them...
The Roller Rocker arm has a different moment of inertia; the valve spring has to overcome the open and close motion of this arm at different RPM speeds... What controls this motion??? The valve spring controls this motion, and inherently controls stability of the valve train...
Obviously we know now that it is not impossible to run the non roller cam in a roller engine; I now know it has been done. The engine may run, but it may not run efficiently or the way it was designed (i.e. valve float).
