3/4 race cam

[73-charger-383]

k........i've got a problem.  I'm looking to trade my old 68 chevy pickup for a 74 dodge pickup.  The pickup has a 72' 440, with 906 heads, edlebrock intake (not sure what one), a new weber 750 cfm carb, headers and a 3/4 race cam.  What would the duration of the cam be??  I've seen them advertised alot with circle track racers around here, but i've never understood just what they were.  Is there a specific thing that makes them 3/4 race, or is it just a generalization that it's not quite an all out race camshaft.  --also, anyone have a guess on horsepower on it for me??  stock bore, no head work, just carb, cam, intake, and headers........i'm just thinking about maybe transplanting it into my 73.

[Silver R/T]

id post this in general tech

[chrisII]

as i understand it it is a throw back term used by cam grinders before they really knew what they were doing, how to properly mesure a cam. and aslo in that time period there customers had no clue what duration , lobe seperation ect meant.when i hear people throw out the term today i instantly think "ok this guys talkin out his azz"  it probably idles poorly but makes more hp than stock, if all else is working properly. if it was me i would pull it out and install a new cam for what i want the engine to do. it would be time and money well spent.

[Charger_Fan]

Whenever someone tells me that, I reply with..."So, it's a cam that lets you get 3/4 of the way down the track, before it falls on it's face, right"?.   And they're standing there going...

I have no idea where that term came from, I assume from some time back in the 30's or something...same thing with using "shellac" on gaskets for a sealer & toilet paper rolls for oil filters. Just plain nuts.

[Old Moparz]

Yeah, I've nodded my head as if I knew what the hell a 3/4 cam was when someone mentioned it.     

This looks handy:

http://www.100megsfree4.com/dictionary/car-dict.htm

three-quarter cam:
A type of camshaft for race car engines which increases lift of valve, speed of valve opening and closing, length of time valve is held open, etc. Also called full cam, race cam, or semi-race cam, depending upon design.

[rare69]

general term for bigger cam. thats about it.

[deputycrawford]

I've never raced 3/4 of a race. I usually finish the race. I usually ask if its a 6 cylinder cam if its only 3/4 of a cam for a V8. That usually gets the person to walk away and blow smoke up someone elses behind. 

[is_it_EVER_done?]

I was able to ask Ed Iskenderian this exact question in the 60's. The term came about form the late 40's early 50's lakes racers in Southern California (Ed "Isky", Chet Herbert, Vic Edelbrock, and other speed pioneers). Since valve lift has an absolute limit in a flat head engine, a cam ground for maximum lift for lakes racing was called a "race cam" (makes sense).

These worked quite well on the dry lakes, but were a bit much on the street, so toned down versions were made for street use which were roughly 3/4 of the absolute limits of lift, ramp rate, spring pressure, etc. that the lakes racers were using. -- These "3/4 race" cams became the first ever production aftermarket cams, and the term/description was logical and descriptive for the time. However, anybody that uses the term today, has absolutely no automotive knowledge whatsoever, and anything that has been done to your engine, is pretty much guaranteed to be wrong.

I would toss the "3/4 race" cam thats in your 440, and buy something that you know what it is. That way you can match it to the lower compression of a 72 engine and degree it in properly. This will provide you with much more power and performance than some unknown cam; with no specs; slapped in without regard for the proper "degreed" centerline; and is guaranteed to be too radical for the engine specs.

Hopfully the rest of the engine is stock and hasn't been treated to similar improvements.

[Chryco Psycho]

 
definatly the terms was born with the flat head engines in the 50s  , 1/4 race & 1/2 race cams were also available

[69fuchs]

I pulled a cam out of a 1962 poly 318--it had a 58 2X4 intake on it, a mallory dual point dist, and edelbrock finned alum valve covers.  The cam had 3/4 stamped on the end, nothing else.  We measured it in some v blocks with a dial indicator, did the math for the rocker arm ratio, and came up with a .470 lift cam.  Not very radical, but not stock either--.400 was stock on these poly engines.

I believe that the term was used in generic way to describe how big your cam was back then, and since I have a cam that has 3/4 on the end, I would say that the term was created OR adopted by the cam manufacturers at some point.

[firefighter3931]

Ya, i used to run 3/4 race cams in everything....weed whackers, lawnmowers and especially snowblowers ! 

Ron

[Charger_Fan]

You know...I've been waiting 25 years for someone to tell me what "3/4 race" meant! That makes perfect sense & is about what I was assuming it meant. Thanks Man, now I can die a happy man.

So...now what about "shellac" on gaskets? Did they really use wood varnish before there was gasket sealer?

[chrisII]

So...now what about "shellac" on gaskets? Did they really use wood varnish before there was gasket sealer?

   i think it would prolly work..i have used spray paint on head gaskets for years. on the blue fel pro ones you can re ruse them several times in low comp applications without ruining them. simply paint the gasket with a spray bomb , and bolt the head on with the gasket still wet. never had one blow. the paint fills in any flaws and seals the gasket, but peals easly when you take things back apart.

[Ghoste]

A local speed shop used to have a cam that they had cut 1/4 of the lobes off and mounted it on a plaque that said 3/4 race cam.