[65WJ]

What does this mean? I heard it again today from my sisters friend who (allegedly) had a 67 corvette with a 3/4 cam. I asked why you running on 6 cylinders? He could not explain what it really is.
So can someone explain what the definition of a 3/4 cam really is.
I would just like to know
I figure it's some kind of chevy talk for ?

thanks

patrick

[Greg Reid]

Been hearing that all my life...I've wondered myself.
The web is a wonderful source of info-

What's a 3/4 Race Cam?

In the early 1950's the most popular original camshaft designers were the legendary Ed Winfield, the father of hotrodding, and Cliff Collins of Harman-Collins. If you look a Huntington's 1951 book you will find the specs for their cams listed. We've also listed some of their cams on our Flathead Performance Cams page. There were lots of cam grinders that copied Winfield and Harman-Collins cams, but these two were the designers and innovators in the early days. It was popular to refer to cams as a 1/2 Race or Semi grind and a Full Race grind. Later, there was a call for an intermediate grind between these two. To fill this demand, Ed Winfield took the intake lobe from his full race cam and the exhaust lobe from his semi cam and called it a 3/4 Race cam (see Flathead Performance Cams). It was literally half way between a full race and 1/2 race cam. Since that time, 3/4 Race has become a generic term for a high performance street cam, i.e. something less than a race cam.

Here's where I found the info- http://www.tildentechnologies.com/Cams/Take_34Race.html

[Pontirag]

I've been doing old cars since the early 70's and heard that term thrown around alot back then but never understood what it meant, often the person using the term new little else about thier car.

[Brent Flynn]

Has 12 out of 16 lobes? hehe

[chipster]

Almost a race cam but not quite...
For the last 35 years or so, when you hear someone talking about a "3/4 race cam," it's just a good indication that they don't know what they are talking about.
Back in the mid seventies though, I remember that J.C. Whitney had "3/4 race" cams in their catalog, along with "full race." Nowadays, I think the acceptable terminology would be "Street-strip."

[rick840]

Kinda like the term " it has an RV cam in it". Does that mean you can only use it off road

Rick

[Pontirag]

Originally Posted by rick840

Kinda like the term " it has an RV cam in it". Does that mean you can only use it off road

Rick

or pull your boat out of the water with your Winnebago 'cause ya got the RV cam

[chiphead]

The last person to (seriously) ask me about a "3/4 cam" was about 70 years old at the time.

Don't you know that the 3/4 cam is best used with the six pack and camel hump heads on a
327 from a corvette with ram's horn manifolds and cherry bombs?

[Jim Scites]

I was told by someone older than me that it meant it was raced 3/4 of the time and 1/4 of the time was street time. I guess he didn't know what he was talking about.

[HaloMedic]

Originally Posted by Greg Reid

Been hearing that all my life...I've wondered myself.
The web is a wonderful source of info-


Here's where I found the info- http://www.tildentechnologies.com/Cams/Take_34Race.html

Greg got it right , this term was used alot in the 70s, days before all the specs terms of today ie lift, Int/Exh duration .

[Overkillphil]

Been hearing it most of my life as well. And it still makes me laugh when I hear it. Often used with other elusive products such as "Elderblock" intakes and "Ranchero" springs.

[Tim Corcoran]

I remember back in the 60's I had a 1/2 race cam in my 62 Oldsmobile, it had a .030 over 394 and man did it sound mean with that cam. In those days the average hot rodder or wanna be hot rodder had no idea about duration, lift, LSA etc. All they know was that they wanted a hot rod and wanted more horse power. So the guy at the speed shop that knew maybe a little more than Joe Blow off the street would recommend a camshaft. The guy would say this is a 1/4 race, half race or 3/4 race cam depending on which direction the wind was blowing. In those days the average hot rodder had no clue about cylinder head flow, torque curve, high stall torque converters and the like. So we had a 1/4 race or a 1/2 or a 3/4 race cam. It was the magic ingredient to make you go faster and sound cool. You hear that guy's engine idling you knew right off "he had a cam in it". We have come a long ways and the average guy knows more about engines and cars in general than back in those days. It's all part of evolution, we can make fun of them but that was a different era.

[Bill Hanlon]

This goes back at least to Ed Winfield flathead Ford cams in the 1950s. They offered "full race", "semi" (aka "half race") and eventually "3/4 race" cams for Ford/Mercury flathead V8s.

A stock '50 Ford V8 flatty cam had 239 degree intake duration, 241 degree exhaust duration and .307 lift on both intake and exhaust.
The Winfield "full race" cam had 260 degree duration on the intake and exhaust lobes with .305 lift.
The Winfield "half race" cam had 252 degree duration on the intake and exhaust lobes with .295 lift.
The Winfield "3/4 race" cam had 260 degree duration and .305 lift on the intake and 252 degree duration and .295 lift on the exhaust lobes.

So the 3/4 race cam had "full race" intake and "semi" or "half race" exhaust lobes.

[psw]

In 1983, I bought a '66 GTO from an older guy who was moving cross-country. He was towing it behind his late 70's Caddy, when the Caddy's tranny went out in my home town, prompting him to sell the GTO in order to get money to fix the Caddy. That is when I first heard the term: "Son, it's got a high-compression 400 and a 3/4 race cam. It'll really scoot!" I was 15 and had no idea what he meant, but it sure was the fastest car I had ever been in at the time. Blew the doors off the typical late 70's Cameros that were thought of as fast in my high school at the time...and it was far more lopey than anything I had heard at the time. Now mind you, I did come from a racing or hot rodding family, and had never even been to a drag strip yet.

After that certain people would hear the car and say something about it having a 3/4 race cam. It was certainly a fairly common way to describe a lopey camshaft appearing in a street car back then, and back them, not many cars had lopey cams, at least not around my parts (Houston suburbs). The funny thing is, to this day, I still do not know what kind of cam that was and what it's actual specs were...

[blueghoast]

Heres one for ya; Got a 32 three window coupe
with a 327 202 heads 3/4 cam and juice brakes.
Fast as hell and'll stop on a dime. LOL
Got that one from my brother inlaw when I was a kid.
Still cracks me up, And he did have some fast cars
back in the day.

GT.

[rexs73gto]

I hear this all the time also. It has a cam in it , just like tim said. I has to have a cam in it to make it run. No Cam No Run.

[zeebo]

Originally Posted by chiphead

The last person to (seriously) ask me about a "3/4 cam" was about 70 years old at the time.

Don't you know that the 3/4 cam is best used with the six pack and camel hump heads on a
327 from a corvette with ram's horn manifolds and cherry bombs?

hee hee hee! yeah, but six pack is what mopar called their triple carb setup..i forgot what chevy called theirs...??

dont forget the 4.11 gears and posi!!

[Jim Hand]

The original Crane Company listed a 3/4 race cam in their 1992 inverntory. I was invited to attend a Crane presentation on cam selection in 1992, and among the handouts was a floppy disc with the complete Crane listings. And also received a certificate for attending. I had the Pontiac cam listing printed out, and will post the 3/4 race cam specs, along with the floppy and my "diploma" as a cam selection "expert"!

The cam specs are:
226 intake and 236 exhaust on a 106 lobe separation, and with the intake centered at 101 with the exhaust at 111. This would be a foul idling cam on any stock Pontiac and especially on the 389/400 series. It would also have a shorter operational RPM range then most Pontiac "performance" cams.

The information in above posts about the origination of the term "3/4 race" is what I have heard/read over the years.

Jim Hand

[nkowi]

Originally Posted by Jim Hand

The information in above posts about the origination of the term "3/4 race" is what I have heard/read over the years.

Jim Hand

Ya, but what the hell do you know?

[badlefthand]

Surprising what we learn from the new generation about how it was in 50s ,60s and 70s,and what the hotrodders knew in the day.Wonder how they gained so much knowledge.