Jamo Roller cams like Pat said will make more HP than a flat tappet. Joe is very fond of the H&M 610 cam, Great tork and good HP. With this many cubes this motor is big enought to rotate the world. Dick better have spare tires
I have called and e-mailed H&M and get no reply from them. If the valve ramps are not servere the roller will work better. You need to limit the rpm level. Running 700 pound valve spring is what is hardest on the motor and cam wear. I am surprised that Joe is not going with a roller bearing cam motor. Nascar uses this. Dick is going from a 431 motor to 496, this cam is going to be 10-15% larger, for the best power. I'm going hydro roller cam crane 587-607. I am going with light valve springs, the motor is not going to see over 6200 rpm. A roller lifter causes less friction than any other lifter but a Schubeck. Price on Schubeck is 2-3 times more, but the wieght is 1/4 of a steel lifter. You should look into a custom cam for the motor to get what you want. Great Tork, flat band from 2500 rpm to 6000, and HP from 3250 to 6250 rpm with a shift point at 6500 rpm, Msd chip the same 6500 rpm. This should be all the motor your cobra will take and still be drivable. More is not allways better. Rick Lake