The story goes that Isky bought a used cam grinder and coppied the profile at the valve from an old indy engine to do the same for a ford flat head. I went to a milder engine in my T bucket, am now running a hyd Mustang gt cam. It works for pump gas but just doesn't sound right. The old isky sounded like a fuel dragster , 3 carter wcd carbs, same flow as 7 stromberg 97's , . a 2 inch tube lake style headers.. I think the cam was about 315 and a 520 lift. Isky's theory was that a 1.5 rocker has less rotational mass and the cam has more bump to compensate for it but it can accelerate the valve opening speed so they get open sooner, more area below the curve so it will breathe better and have more low end torque yet be able to rev higher. the same theory for the factory roller cams today. the previous engine in the t bucket was a 300 horse 390 with the 3 2's, isky and headers. It would always heat up. it only had about 30 k miles on it I traded off the long block and the guy tore it down and said one head gasket was on backwards so the water only was pumped in the front clyinders, he put it back together with a 4 barrel and into a 64 mercury and said it would rev forever. then the car was in a tow yard and i should have bought the engine out of it. I bought a ford van out of the company motor pool the repair history only showed oil changes but it never ran right(460) At 90 k miles i pulled the motor and found parts of a rod bearing in the pan. So much for the company( ford) employee discount car buying plan. It was the only one I kept that long nornally I usuallybought one from the motor pool at 6 month to a year old, drove it for a year then sold them at my original cost.