Does the duration give you higher rpms? If so, can someone explain in english how rpms are affected by the different cams?
Ok, so it looks like more overlap lets you rev higher? Why? Not so much negative pressure on the engine with closed valves during the duration of the cam?
If your looking for a stripped down simple explanation for the ins and outs of how cam specs affect engine performance, you really won't find a very good one. The things that happen inside an engine because of the cam can be very complicated. The best and easiest way to pick a cam is to know the engine specs you want and call a few cam manufacturers and see what they recomend. They are usually very helpful.
In a nut shell, by opening the valve higher and for a longer period of time in degrees of rotation it increases cylinder pressure by alowing more air in. And more effectively removes it. My understanding is overlap dictates the shape of the powerband. And where it's at.
Duration and overlap gives you a higher rpm range. Lift alone helps in the bottom end torque. Overlap also affects the idle and vacuum at idle. A wide LSA cam for EFI also gives you a benefit with a carb, in that it increases the idle vacuum, which in turn gives a stronger vacuum signal in the carb circuits. I've learned this in running a carb with Ford's last production hyd roller cam,the F4TE for the 5.0's, it's got a 116* LSA and I rarely have to give it a "pump shot" to prime the engine when starting. JUst a bump of the starter is usually all it takes. Power on this cam is from idle to 6000 rpms.
there's lots of rumors and speculations of what makes it all work, but it takes YEARS of research to figure it all out. Even then, things change and you have to start all over again. There's a LOT more to a cam than just lift, duration, LSA, and overlap. A LOT more! whos gonna be the first do design a variable cam timing system for a pushrod V8?
In the near future there will be electric valves that are infinitely adjustable. Wont need that Vtec crap then
The cam itself is not responsible for an engines acceleration ability.How ever the way and amount it opens the valves contributes to an engines acceleration ability(Im' talking RPM here)Through its contributions to VE(volumetric efficiency)Intake tract runner length,carb size,head port size and length as well as valve size and exhaust configuration all contribute to an engines ability to breathe and accelerate.Bore size and reciprocating mass also contribute to an engines rpm potential.Solid cams as opposed to hydaulic cams allow an engine to have a higher RPM potential due to better controll over valvetrain components.Less deflection in the valvetrain as well as less valve float potential due to the use of stiffer vavesprings.I could go on here but these are most of the high points regarding your question.Hope this helps.
