3/4 cam????
Thread Starter
Racer
Joined: Apr 2007
Posts: 275
Likes: 1
From: Lafayette/marquez La/tx
3/4 cam????
I was at the auto parts store the other day. Some people gathered around my corvette. It has a slight choppy idle. One of the guys ask if I had a 3/4 cam in it. I really didn't know what to say as I don't know what a 3/4 cam is. I am kinda semi-old and I have heard this term a few times but never understood what it meant. I also have heard it refered to as 3/4 race cam. Does it mean a .750 lift cam? Does it mean 1/4 of my cam is missing?? Fill me in.
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Really means nothing but there is a history to it. I used to hear it all the time when I was a kid. IIRC someone stated it was related to track and street use, 3/4 track time and 1/4 street time meaning it was more of a race cam than a street cam. 
However I have heard some other explanations...........???
However I have heard some other explanations...........???
Racer
Joined: Jan 2007
Posts: 427
Likes: 1
I knew it to be a race cam in a flat head Ford. You really had a tiger by the tail if you ran three dueces, Edelbrock heads, acorn nuts to hold them down, beehive oil filter on the firewall.
This was just before 'John Milner' had the fastest car in the valley.
Dano,
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Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
In the 60s within block and a half distance from our house a 28 ford two door sedan flat head with a small four barrel. A 32 ford vicky two door chopped 3 1/2" in front 3 " in back, flat head two strombergs. a 55
chevy 265 headers, cam, a 65 mustang hilborn injected 289, a 63
split window fuelie vette. The guy in the 63 vette fell asleep ( so he
said) ran it off a hill totaled it, bought a 67 coupe hit a center devider with it totaled it out.
chevy 265 headers, cam, a 65 mustang hilborn injected 289, a 63
split window fuelie vette. The guy in the 63 vette fell asleep ( so he
said) ran it off a hill totaled it, bought a 67 coupe hit a center devider with it totaled it out.
Pro
Joined: Apr 2005
Posts: 591
Likes: 7
From: Batavia IL
jeeze how old was the guy that asked you that, lol. if someone asked me that about my car, I would have looked at them funny and just said "no its a cammotion solid roller with such and such lift and and such and such duration.
Melting Slicks
Joined: Sep 2004
Posts: 2,412
Likes: 3
Hahaha, a little bit of knowledge is dangerous. I love it when I hear guys asking whether or not motors have cams in them, as if it's an aftermarket option.
Duuude that sounds siiick. I'll bet he has a cam in it.
Duuude that sounds siiick. I'll bet he has a cam in it.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
In the beginning stock cams like for flat head Fords were reground for a hotter profile & 3/4 (race) was used as generic term for more than stock but not a (full) race cam. Obsolete for a long time.
When I was a kid I read everything on cars in several lib. in several towns including hopping up flat head Ford V8s & I don't recall ever seeing a def.
Anyway before my time, have rarely heard it, but when used, they haven't a clue.
By the muscle car era it was no longer in use by knowledgeable guys.
Advertised duration was used. Since some think a bigger no. is always better & the cam cos. wanting to sell cams & have the customer happy & knowing that bigger is not always better for everyone, the Advertised duration kept getting bigger. For example a 290 Advertised duration cam might have less under the curve than another brand's 260. So this had got out of hand & was not good for reputable cam cos.
Harvey Crane of Crane Cams, seeing all of this, promoted the idea of measuring duration at .050 as a means of comparison.
When I was a kid I read everything on cars in several lib. in several towns including hopping up flat head Ford V8s & I don't recall ever seeing a def.
Anyway before my time, have rarely heard it, but when used, they haven't a clue.
By the muscle car era it was no longer in use by knowledgeable guys.
Advertised duration was used. Since some think a bigger no. is always better & the cam cos. wanting to sell cams & have the customer happy & knowing that bigger is not always better for everyone, the Advertised duration kept getting bigger. For example a 290 Advertised duration cam might have less under the curve than another brand's 260. So this had got out of hand & was not good for reputable cam cos.
Harvey Crane of Crane Cams, seeing all of this, promoted the idea of measuring duration at .050 as a means of comparison.
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
When I was in high school there was all this talk about ¾ cams or full race cams. I knew there was more to it than that but really did not understand it but no one else did either. I have not heard that term ¾ cam in thirty years …… man I am I getting old by the way my first car was 53 Ford with a “Flat head”. 
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
in the 60's a popular supplier was jc whitney, don't even know if they're still in business. they listed cams in several performance groups stock, 3/4 race and full race (track). you'd just locate your engine and order the cam that you wanted. i don't remember if they even listed the specs.
now this was a long time ago, when i was young and foolish and the internet was just a twinkle in al gore's eye, and the only people that really had access to real knowledge about cams kept it to themselves. you just would buy a pig in a poke and run it.
i stuck a 3/4 cam in a 69 firebird (my first new car) and surprised a few-if i might brag-z28s!
we even used to swap carbs to see "how it felt". really had no idea what we were doing, just a bunch of kids having fun.
now this was a long time ago, when i was young and foolish and the internet was just a twinkle in al gore's eye, and the only people that really had access to real knowledge about cams kept it to themselves. you just would buy a pig in a poke and run it.
i stuck a 3/4 cam in a 69 firebird (my first new car) and surprised a few-if i might brag-z28s!
we even used to swap carbs to see "how it felt". really had no idea what we were doing, just a bunch of kids having fun.
