The term 3/4 cam was kind of a carry over from the old Ford flathead performance days but as Woody says it can mean any performance cam. Look in any performance catalogue, Jegs, Speedway, Summit, etc, and you will not see any reference to 3/4, full race, etc. What is important to know for your application is who built it, advance duration, lift, RPM range, and type of lifters. Also necessary is compression ratio/intake/carburetion/exhaust and ignition system used. If someone installed a performance cam without taking into account the other factors it is not going to make much difference or run very well.
Fred
