3/4 and Full Race Cams

Every once in awhile I still get a call from an old school racer asking about a camshaft for his hot rod. I can tell his age from his question.

"I want a cam that will give a little thump. You know: aaarrrrump, aaarrrump, aaarrrump. Not a full race cam, just a three-quarter."


I think a guy named Bill Winfield invented the term "3/4" cam, but if that guy had a dollar for every time some hard ankle ordered one he'd live in Bill Gates neighborhood! So what is a "3/4" cam?

Originally a 3/4 cam was a specific grind. It was halfway between a "semi" cam and a "full race" cam. Keeping in mind that there was little technology back than and anything other than stock was an improvement. You had three choices for higher performance: semi, three-quarter, and full race.

During the sixties, when the high performance business started to blossom, many new cam manufacturers (grinders) started popping up and several different grinds were appearing in the marketplace. At that time each grinder might have ten or twenty different grinds spanning an array of specs for small block Chevy. Today each might have a hundred different grinds.

At that point the terms "full race" and "3/4 race" lost there meaning because a "3/4" cam was not an individual cam at all. It was any of a number of different grinds that had some characteristics of a racing cam, like the sound it produces through the exhaust as it lumbers at idle. But it retains the drive ability of a street cam. There are a plethora of cams that will fit in this range. So technically speaking they could all be "3/4" cams.

Back in the BC (before computers,) we kept a small block Chevy cam that was broken off at the fourth journal just for the guy that came in asking for a "3/4" cam. You should have seen their faces when we pulled it out and placed it on the counter in front of them. This would happen two or three times a day.

"There it is," I'd say, "three quarters of a cam!" Then we would wait for the customer to laugh and all follow suit.

Once I ordered a bunch of generic small block Chevy cams and had the box labelled "Full Race" on the more aggressive grinds and "3/4 Race" on the street versions. From that day on when a customer asked for a "full race" or a "3/4 Race" cam I had it in stock!

Have you ever bought or sold a "3/4" Race cam? Let me know in your comments.