Terminology was a big thing back then, it helped if you didn't know what you were talking about, you could spew a few "facts", and if you sounded convincing, the rest in the group would nod and agree. Cam lore was a "black art". Very few really understood what it was all about. Kind of like today. Stock cams were just that, stock cams, everybody just knew, that there was something better than those. Full race cams were just to much for the street. So the idea of the 3/4 cam, or 3/4 race cam was born. The grind could be anything, as long as it was hotter than a stock cam. The reason no body can tell you what it was, nobody really knows. There wasn't a set of numbers to grind a cam to that made it a "3/4". The cam grind was somewhere between a stock cam and a full race. If you can get to find some of the older ads from cam manufactures, you will likely see where the cams offered were described as 3/4 race and full race. No specs. just the terminology. That was part of growing up back then, if you knew a bunch of the key words, and if you really did know how some of this stuff worked, you could be a big shot. That's how we all learned, I personally blew more money and time on combo's that didn't work, than did. But I was busy! To busy to get into trouble, except to see if the "improvments" really worked. You can read that as "SPEEDING FLAT OUT" or running the sort of "MEASURED" 1/4 mile that's just outside of every small town, or any town for that matter. You knew it was a real 1/4 mile if it was painted on the pavement!! Yeah, we were a little naive, but it was fun. Not something you can get away with today. So, the short answer to "was there such a thing as a 3/4 cam" yep! But you'll never nail down an exact grind.