3/4 Race?

[jeepguy1948]

Can anybody tell me what “3/4 Race” & “Full Race” camshafts are? And where the terms come from? Is there a 5/8ths race cam? How about a 7/8ths race cam? Stock would be what, 0 race?

 

[mfirth]

3/4 & full race are just"slang" or randum terms. To me, 3/4 race would indicate a street/strip grind for more than stock performance and full race would be for an engine built solely for competition. Some "full race" cams are not practicle for every day driving.
My .02 cents ane hopefully not nonsense .......

 

[Bored&Stroked]

These were terms that really came to be in the 50's - to generally describe the characteristics of a cam's design.

Folks didn't understand technical camshaft characteristics (lift, durations, lobe separation, timing events, ramp acceleration, jerk, etc.), so these slang terms came to be part of the common performance lingo.

The camshaft companies, the magazines, the local speed shops, groups of guys in garages - all used the terms so the common man could "select a cam" for his new engine or act like he/she knew what they were talking about.

Some of it was purely bragging rights - as obviously a "Full Race" cam must mean that your engine is bigger, better faster than the guy who ONLY has a 3/4 race cam. Truth be told, the terms are practically meaningless if you understand camshaft characteristics and how they relate to the overall engine package.

Even today, many of us so-called "Hotrodders" have no clue about camshaft design and how to contrast/compare different lobe profiles or basic designs (flat tappet, radius, roller, etc) . . . so these "terms" will continue to be around.

From a cam selection perspective, these terms mean very little in that there is a WIDE RANGE of camshafts that might be called one of the other - yet operate completely differently.

Lastly, companies like Iskenderian who were up front and center during the "camshaft wars" did a lot of advertising to the common man - so being able to answer the question of "what cam are you running" became part of the common hotrod/racer lingo . . . and it is still here today.

I've heard plenty of guys say "it has a 3/4 cam in it" - but when asked what the characteristics are, have no idea other than maybe the profile name.

 

[51504bat]

How about an "RV" cam?

 

[tubman]

Now that's an interesting concept - an RV with a flathead.

Actually, 25 years ago I bought an old Class "A" Winnebago with a Ford 300 six. The engine was kinda tired, so we rebuilt it and added an Erson "RV" cam that I got from "Dale Wilch Sales". As I understand it, they are designed to produce even more torque down low than a stock cam. Thus it would seem to be a poor choice for any type of "Hot Rod" car. That old 300 really had the grunt though. I used it to pull my vintage race car all over Minnesota and Iowa.

 

[Ol' Ron]

Agin B&S has it. Sometimes trying to explain something is impossible. I learned allot about cams when I was racing. We all had the same rules to follow, so all the cars should be the same, except the learning curve. Sometimes making a mistake is the best teacher. Today I look at the lift and duration, but this can be deceiving. I ran a 400jr for years and the track and engine seemed to like it, after 8years or so the flathead was being retired in favor of more modern engines (SBC???) A good friend of mine said hewas going to build a new engine for the following year and said he had a cam frrom Sig Errson that was much better than the 400jr and he had worked for Isky, so knew something about cams. I bought it, looked at the numbers and wasn't impressed. Lift and duration were about the same.
Half way through the season, we had a rain date so Norman and I changed the cam1hr/45 min one 6 pac, and she started up. I was not impressed with the sound either.
However at the track it was a different story. When the driver came in from the warmups. He told the chassis man (Bob Counio) it's loose!!!
The cam made a big difference , I have no idea why??

 

[jeepguy1948]

Thanks All!

 

[Pete]

Nowdays cam definitions.

RV = stock with a fancy name.

3/4 = stock with a different name.

Full race = OEM core with slightly modified timing for "lopey
drive-in idle".

Super race = OEM core reground for stop light racing.

Super duper all out go fast race = A steel billet race cam designed for top fuel drags, Bonneville or 1/2 mile dirt sprint car racing.

 

[millersgarage]

3/4 cam is from a V6

 

[B-O-B]

Sometime around 1950 I did a lot of street racing I had a 48 Ford convertible & Harmon Collins was advertising a 3/4 race cam. Their words not mine. I rebuilt my 24 stud engine & put one of their cams in,carbs,milled heads,headers. It ran OK but I should have chosen a better cam for street racing. I didn't lose very many races but I think it may have been because of my speed shifting. I hardly ever used the clutch & the column shifter was bent to about the 12:30 position . Just burp the throttle & jam it in 2nd. I felt sorry for whoever bought that car. Then came the 50 chevy vert with the jimmy. Another time. Another story.

 

[Pete]

Sometime around 1950 I did a lot of street racing I had a 48 Ford convertible & Harmon Collins was advertising a 3/4 race cam. Their words not mine. I rebuilt my 24 stud engine & put one of their cams in,carbs,milled heads,headers. It ran OK but I should have chosen a better cam for street racing. I didn't lose very many races but I think it may have been because of my speed shifting. I hardly ever used the clutch & the column shifter was bent to about the 12:30 position . Just burp the throttle & jam it in 2nd. I felt sorry for whoever bought that car. Then came the 50 chevy vert with the jimmy. Another time. Another story.

Up here "button" shifting was popular. A kill button on the gear shift knob. You kept the gas on the floor and just "burped" the button.
An old trick borrowed from motorcycle racing.
It sounded just like a Lenco shifting.

 

[petehoovie]

Sometime around 1950 I did a lot of street racing I had a 48 Ford convertible & Harmon Collins was advertising a 3/4 race cam. Their words not mine. I rebuilt my 24 stud engine & put one of their cams in,carbs,milled heads,headers. It ran OK but I should have chosen a better cam for street racing. I didn't lose very many races but I think it may have been because of my speed shifting. I hardly ever used the clutch & the column shifter was bent to about the 12:30 position . Just burp the throttle & jam it in 2nd. I felt sorry for whoever bought that car. Then came the 50 chevy vert with the jimmy. Another time. Another story.