Thread: How about this cam in a 283?

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The motor is indeed just a pump. Consider that your lungs are one cylinder. You open your mouth and breathe in a lungful of air, then you close your mouth. You have trapped the maximum amount of air. If this air were an explosive mixture, you would get the max amount of push on the piston. Now, let's say that as you were taking a breath, you didn't close your mouth and started to breathe out. You would lose a lot of the air that you just breathed in and once you did close your mouth, you would only have a fraction of the combustible mixture that you might have had if only you had closed your mouth at the right time.

So it is with a cam. You have to know when to close the intake so as not to push the mixture that you just drew into the cylinder back up the intake tract, thus losing some of the bang and also disrupting the vacuum signal to the carburetor.

To answer your question about a blower, I think you'll find that in talking to the blower guys, they'll tell you that you really don't need a hell of a lot of cam to make a blower motor work. Just a little over stock will work real well.

Back to being just an air pump..... the more cfm of air you move through a motor, the more horsepower you can make. In order for a 283 to make as much power as a 350, you have to spin it faster. A 350 turning 6,000 rpm's will take in 607 cfm. To take in the same amount of air and theoretically be capable of making the same power as the 350 at 6,000, the 283 would have to turn 7,400 rpm's. Now, here's where the rub come in.....you can't use a regular street grind cam in the 283 and spin it 7,400. A 9.0:1 283 with the proper cam will make power to about 5,000 rpm's, so you are out of cam and you need to spin it another 2,400 rpm's to make the power that you could with a low-rpm 350. So, you say to yourself, well, I'll just cam the hell out of it and it will rev to 7,400 and make power. BZZZZZT. Wrong answer. The intake closing point is so late on this l-o-o-o-o-ong cam, that you are not capturing enough compression to make a decent bang when the plug fires. In order to make this cam work and make power to 7,400 rpm's, you would have to increase the static compressio ratio to something on the order of 11.5 or better. It's late and I'm not figuring all this stuff out to the letter right now, but I hope you get the idea of what I'm trying to say.

If I have not made this clear, please say so. I have a lot of patience and will keep giving examples over and over until you guys understand this cam thing.

Shawnlee gets it, you other guys can too.......