Join Date: Jan 2000
Location: Sequim, Washington
The terms 3/4 race and full race predate the sbc by a quite a few years. I remember hearing the term "full race" around 1950 relating to a built up flathead in a '35 Ford coupe.
Cam grinders only made a few different cams. They were handmade, and the grinder reset for each lobe. Just a few cams per day. Ed Winfield actually ground different profiles for some lobes on the flathead Ford cams to make up for differences of flow from port to port. This would have been his "full race" cam. It was meant for nothing but competition. High compression, ported and relieved [flatheads], multi carbs, open exhaust stuff.
The 3/4 race cam would be a hot compromise cam. Sort of "hot street" in todays terms. It would work best with higher compression ratios and multi-carb manifolds, but could get you away from a stoplight ok.
As the market for hot cams got better, cam grinders would have more "full race" cams available designed for different kinds of racing, but all without compromise for street use. They added more street cam profiles under the 3/4 label. Even Sears had cams listed in their Catalogs, and I bought a 3/4 cam from them for my first car. There was no real science to our choices. Pretty much pot luck. I decided I needed a 3/4 cam, and Sears sold one for 10 bucks.
Things change. When the "Duntov" cam was released in '56, it was a "full race" cam in our eyes. With .400 lift, it allowed us to crank a 265 or the new 283 over 6 grand with ease.