When we assembled John's 261 last fall, we installed and degree-checked a "261/Corvette" cam made by Elgin Industries. It's their part number E-293S. The "advertised duration" is 290 degrees, which would indicate it's a fairly radical racing cam. Actually, the duration of the valve opening is around 260 degrees, making it equivalent to an "RV cam" which increases low to midrange torque and gives a slight, but noticeable improvement in cruise power without adversely affecting idle smoothness or manifold vacuum. Their "290 degree" specification includes the clearance ramps on both ends of the cam lobe, when the valve isn't actually open. The only difference from the OEM "Corvette" cam I can see when checking the cam with a degree wheel and a dial indicator is a slightly different valve lash adjustment.
John can give you a "seat of the pants" evaluation of the difference in performance he has seen, as we didn't have a dyno handy to document any "before and after" power measurements.
Jerry
