What you all think, cam basics...

[gettingreasy]

I was over at moparts.com and there is a post about cams and this was mentioned. Some like to use smaller cams(240* @ .050" was given)to maintain cylinder pressures and not to rely mostly on the overlap for scavenging, but more air velocity through the intake tract to improve efficientcy. So what do you horsepower savvy folks think about this? More overlap or more air velocity?
-Jesse

[AHotRod]

It depends on the engine, rod length and stroke (rod/ratio), the cylinder head design, the exhaust system (headers-free flow vs street exhaust), and the "real" compression ratio.
So to answer your question, one would need to know what we are working with, Engine, Trans, rear gear, tires, overall weight of the car, etc.
To assume, is to be incorrect.

[Glen]

street-ab-bility and spunk are unknown numbers without lobe seperation angle.

[Noname38]

[ QUOTE ]
It depends on the engine, rod length and stroke (rod/ratio), the cylinder head design, the exhaust system (are working with, Engine, Trans, rear gear, tires, overall weight of the car, etc.
To assume, is to be incorrect.


[/ QUOTE ]


The man has a point

[gettingreasy]

No, you guys took this the wrong way. What would be best, not on any perticular motor. I was just wondering what some thoughts are on a big overlap for the scavenging versus natural super chargeing of high intake velocity? Just want some opinons or some pros/cons from some engine builders on the theory of this.
-Jesse

[JOECOOL]

The natural scaveging or whatever you want to call it is only effective at high rpm's. Short overlap and higher cyl. pressure at low rpm's will make everything but a full time race motor more driveable ,more torque and a lot more fun. The question you have asked needs a couple of more pages of info,such as weight of vehicle,gearing ,heads, carb, convertor. I tell my friends the best way to pick a cam without all the specs. is to pick the one you would like and then go two or three steps smaller.
In my opinion most performance street cars and a lot of race cars are overcammed.Having a torque curve starting at 3800 rpm is not much good when your cruizing at 2600 rpm.

[C9]

For the street, including a degree of reasonableness -

Little engines = big cams.

Big engines = little cams.

[gettingreasy]

Agin it's not for any particular motor. Just some sound theory would be nice. I'm being VERY general here. If you guys want an example motor take this senario; 440 RB, 10 to 1 compression, with port matched and cleaned heads stock heads with stainless one piece valves and moderatly stiff springs, stock electronic distributer with a performance curve and an ORANGE box control module. Drivetrain; 727 manuel valve body, 2800 stall, Mopar 8 3/4 rear with 3.91's with a locker, and 28" tall tires. This car weighs lets just say 3400 lbs. Now what kind of cam would be best and what kind of intake/carb would give me the best performance. Again this is not a real car(yet) so you can change all the variables, even wieght as long as it still weighs some were near 3000. Thanks and sorry for the confusion.
-Jesse