The Stovebolt Site Forums The Shop Area Engine Shop 3/4 Racing Cam in 283 CID Engine - Questions

1. Precisely what does a 3/4 racing cam do?
2. Whatis the effect?
3. What are the consequences of havig it? (Idle smoothness, milage, lookouts, gotchya's, etc.)

Back in the day when people used to warm over a 283 the basic mods were a slight bore (.060?) to get a 301, add a big 4-barrel or 3 twos and throw in a 3/4 cam and solid lifters. The cam will give you more HP and lope up the idle a bit, just enough to sound good.

The term "3/4 cam" can mean many different things, but simply put it's a cam that improves performance but is still suitable for street use. Racer Brown, Clay Smith Cams and Isky were players at the time but one of the favorites when I was a kid was the one from Corvette engine, the legendary "Duntov" because it was very streetable and available at your local Chevy dealer's parts window.

That cam was named after Zora Arkus-Duntov perhaps THE most significant individual in the history of Chevrolet product development. He developed the cam and fuel injection for the first V8 Corvettes, but his spirit and determination immortalized him.

If you're doing this to your '59, you will indeed be true to the car's history.

Google Duntov, it's an interesting story.

Had a 283 in my 56 coupe during high school and ran exactly what Czechman said. I ran a Duntov cam(correct about Arkus) with a nice Rochester and if I remember correctly we bored it to .120 to get the 301. Back then most folks said it couldn't be done but let me tell you......it was a "haint" back then. I didn't sweat anybody in my class and most of the time had to run "over my head" to get someone to race or at least spot them a car lengh or two.....of coarse I didn't run around town tellng everyone what it was bored to ect....OOOh, the good old days!

The term 3/4 cam was kind of a carry over from the old Ford flathead performance days but as Woody says it can mean any performance cam. Look in any performance catalogue, Jegs, Speedway, Summit, etc, and you will not see any reference to 3/4, full race, etc. What is important to know for your application is who built it, advance duration, lift, RPM range, and type of lifters. Also necessary is compression ratio/intake/carburetion/exhaust and ignition system used. If someone installed a performance cam without taking into account the other factors it is not going to make much difference or run very well.
Fred

What it won't do is add as much performance as a set of good heads will add. Cams can provide the lope sound many desire just for the sake of it or they can provide added torque as specific RPM ranges. A lot of money has been spent on cams when it could have been put to better use on the heads and exhaust.

A lot has happened in 50 years of high performance modifications and today the options are well researched and seemingly endless but if he wants to build an engine that is true to his truck's era, and will garner some misty eyed old fellows like me, he couldn't do better than build one more "301".

Sure, there's a lot more that can be done, but in it's day a warmed over 301 was a strong runner and you didn't have to break the bank to make it happen.

It wouldn't be a sin to throw in a set of headers and some "cut-outs" just for the fun of it. I used gas tank filler necks for my cut-outs. I couldn't afford those fancy cable-operated ones that you could buy from JC Whitney.

Well, I see we're all geezers here. Czechman hit the nail on the head. Bought my '59 sight unseen, figured I'd have to rebuild the engine. Wrong. 180-184 psi per cyl, quadraject carb,HEI, different manifold intake, and quad-pipe dual exhaust headers, hydrolic lifters, the whole nine yards. Bet it doesn't even have 1,000 miles on it. I'm leaving it as is, except replacing the four pipe headers with the original ramshorn exhaust header (but keeping the dual exhaust because my shopmate keeps harassing me about balancing the "breath in/breath out" needs of the engine. He's kind of a screwball, but often right. Thanks for the responses - tremendously interesting. Gregg.

I had one too in my original 57' fuelie back in the day but you are mistaken on the bore required to get a 301..it takes a 4" bore and that is .125 where I went to school. I know of several 283's that had walls too thin to punch out that far and would run very hot. Best be careful if it's a 57' block. Later model's had thicker walls I've heard. Mine had 12.5/1 Jahns and would only run on Sunoco 260 w/o retarding the timing and then it ran terrible.

the earliest 283 blocks [57/8] can be bored .120 IF they don't have any corrosion in the water jacket, otherwise they can run too hot - the heavier 59 to 62 blocks can safely be bored to 4", but the 63-67 blocks shouldn't be bored more than 0.60, back to thinner walls

Bill

It depends on what you want,,if only a lopey idle then get a hyd cam,,if you have an auto trans and install just a cam and no other your power will not be what you want as a big cam and standard auto do not work well,,if you have a stick that is good but low end torque will lag,,if you want to go fast more cu inches is the way,,,383 or 350...doc

Don't trash a good 283 block by boring it .125" oversize- - - - - use a 350 block with a set of adapter-type main bearings to run the 283 crankshaft. There's a set of thick wall mains available to use the small-journal crank in a 350 block, just like the ones that adapt a 350 crank to a 400 block. With a set of 6" long H-beam connecting rods, that little 301 will turn 8,000 RPM all day and never miss a lick! It's even possible to get a few more cubic inches than 301 (306 to be exact) with a .030" overbore in the 350 block. The short-stroke crankshaft is the secret to the super-high RPM.

King's Crankshaft in North Carolina will build a 3" stroke super-lightweight crankshaft, 38 pounds instead of the standard 55-lb. weight, and provide the rods and pistons to match. I think the last time I priced that rotating assembly, it cost approximately $5,000.00. It would make some serious RPM in a round track engine, though!
Jerry

53moneypit: your right. It was .125 but hey, its been 44years ago!! I never had a problem with it running hot and that engine lasted almost 2 years...UNTIL my brothers slipped it off to Shady Sied Dragway one day while I was in the hospital. They did run it hot and it cracked #3 cylinder almost the entire length of the bore. For its time it was a hoss. The only problem I had was the rocker studs would work up a little and require re-adjusting ( I had never heard of putting pins in them or screw in studs.....but hey, I was just a kid and didn't know all the other stuff I later learned but it don't mean I didn't enjoy every minute of it.
Nice comments Hotrod Lincoln.