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Old 02-28-2013, 07:34 PM
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What size cam is a 3/4 cam

Hello fellow hot rodders, this is my first post on here. I've got a 350 4 bolt bored 40 over that me and my dad built 15 yrs ago. My dad said it has a 3/4 cam but I know that's old hot rodders talk. What size is a 3/4 cam and what would be a good set of heads to go with the cam?

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Old 02-28-2013, 08:10 PM
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Last 3/4 cam I saw had just rolled off the table!

Seriously there is no way to give a spec. It was a much miss used term way back when. Probably a RV cam or just a bit hotter in modern terms.
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Old 02-28-2013, 08:12 PM
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old term to me. means a street cam not all out race.
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Old 02-28-2013, 08:17 PM
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Thanks, I'm just gonna use my digital calipers and see what it is. Any suggestions on some heads?
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Old 02-28-2013, 08:36 PM
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maybe is a V-6 cam?lol. 3/4 race, rv-cam(todays version) just none sense names given by people that do not understand anything about cams
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Old 02-28-2013, 08:43 PM
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I think "3/4 race" was the laymans way to identify a cam that you could brag about but not actaully race with

It gave you a 25% cushion to come up with an excuse if you lost a race as compared to running a full race cam, you had no out.

I think crane still labels some of their cams this way

(not saying your dad was trying to BS anyone, I am generalizing

Last edited by Custom10; 02-28-2013 at 08:52 PM.
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Old 02-28-2013, 09:03 PM
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3/4 cam meant the open duration was 75% of 360 deg. Like 270 deg.

A real inexact way of determining cam grind. A 268 cam would be a 3/4 cam example.
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Old 02-28-2013, 09:29 PM
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Well its a term a lot older then me!!!
In Detroit as a boy my Dad and his hot rod buddies in the early 50s used to take old stock cams down and have them reground and called it a 3/4 grind it was street slang there was a 3/8 reground cam and 3/4 reground cam! The 3/4 cam was the amount of material it looked like was left after regrinding heal and lobe! After grinding they looked like about 3/4s of the original cam lobe left creating a higher lift and creating a quicker opening and closing.

My dad and friends always said "man it looks like only 3/4s of the old lobes are left!"

The 3/8 cam when you got it back looked like there was bout 3/8 taken off the heal creating higher lift only!

Just street names no real measurements for the usual cam regrinders work done!

That's the way it was told to me in the 50s by guys that are long gone and my Dad that passed a few years ago What it means elsewhere I cant say but at the tracks in the 60s the old guys running Ford flat heads said the same thing! 3/8ths and 3/4er regrinds.

But now its been adopted to a term pertaining to new cams and I don't know why The old street slang term for a regrind meant a "BAD A$#" cam. Maybe that's why the terms adopted in this day and age! I thought 3/8 and 3/4 cams faded away years ago!

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Old 02-28-2013, 09:45 PM
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thats before my time.The first time I heard 3/4 race it was said by a street worm wannabe and I never ever took it seriously. I remember when regrinding stock cams was a standard thing. Up here,Shadbolt cams still exists and they regrind a lot of cams
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Old 02-28-2013, 09:54 PM
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I didn't know anyone even used the term 3/4 cam anymore? Unless reminiscing of the by gone age when our fathers were young! 1 0r 2 old grinders are still in Detroit too Vinnie and a couple of black smiths that still do straight axle straightening and caster camber! Now that's a dieing trade black smith

Jester
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Old 02-28-2013, 10:03 PM
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PJ. I remember pitting for a roundyround car ,I think they were all black smiths because they all have big hammers for everything,lol...

also I have a friend in Clinton BC.He actually gets a black smith to make shoes for his horses.I think you mentioned being around horses before?
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Old 02-28-2013, 10:13 PM
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Yep we raised horses a horse black smith is called a "Farrier" its a little more specialized then a journeyman Black Smith. They make big money shoeing and trimming horses some even do teeth pulling and floating, But they get busted up pretty good too!!! broken arms, feet, bit, kicked, stomped,Etc!

Jester
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Old 03-01-2013, 10:45 AM
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I found on the end of the cam (a179r) stamped on it and and the #'s 210 written above it?
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Old 03-01-2013, 11:17 AM
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KC-179R Speed Pro cam kit (151/L79) cam specs.
@.050 I=222 E=222
@.006 I=290 E=290
Valve lift I=.447 E=.447
LC = 114
Overlap = 78 deg.
151 cam /aka L79 grind , lift .447/.447 duration 291/degrees.

Jester
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Old 03-01-2013, 11:35 AM
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This is good...

At a press conference in 1956, when Zora Arkus Duntov was answering questions about the new "283 horse 283", the question about the cam came up. His response was "It's about 3/4 of the way to a "full race" cam." IIRC, he was speaking of the venerable "Duntov 30-30". It "stuck".

We "heard" the term a lot, but as non-Chevy people, we never paid much attention to it. "We" had McKellar cams... (McKellar #10 was the "real deal" 421SD cam) I too, haven't heard the term used in MANY years.

Jim
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