Issue with Stamped Steel Rockers in BB Chevy

[SSDiv6]

Originally Posted by Jeff Goss

Isn't that a function of duration? They way I understand it, you want the valve to open and shut as quickly as possible. Ideally, you would want the cam "ramp" to increase as steep as possible, then drop as quickly on the back side. This could cause the inherent "bounce" starting at the lifter and reverbrating through the valvetrain. If the spring couldn't keep up, you would get periods of increased lash as the valve tried to keep up. These harmonics cause the "beating" of the valvetrain.

I'm not the smartest tool in the shed, but it seems like when we started to vary duration in Stock, these problems started. I know Chevrolet motors aren't the only ones affected.

Jeff

Not duration, it is the lobe shape and ramp design. There are too many schools of philosophy among cam grinders on what does work and what does not work. I have heard the story of "opening and closing the valve as quickly as possible", which happens to be a tale. You design a camshaft for efficient filling and exhaust based on the particular engine specifications. A stocker cam for a big block Chevy will not work the same on a Mopar big block. One mistake made by racers is believing that all they need is big cylinder flow numbers. Big flow numbers do not mean anything if you do not have the velocity; a good cam is designed with parameters based on 275 ~ 300fps numbers.