Ok. I've gone all over the net trying to understand how cams work and I haven't had luck. I've seen the video on howstuffworks.com and it hasn't clicked for me yet. I've seen terms like:
Intake opens/closes
Exhaust opens/closes
Intake centerline
Exhaust centerline
Duration
Lobe separation
Lift intake/exhaust
Overlap
Operating range (Also seen this as RPM)ex 1500-6500rpms
Redline- ex 6500
RR
Gross Lift
LSA

Can anyone tell me what these terms mean and what they actually determine? I'm sure this is a pain in the *** question but I'm reaching the final step of my build and my tuner tells me that I'm going to have to cam it if I'm going to reach 600+rwhp so I need to know what cam is going to be best for me and I need to educate myself so I can make an informed decision. I've seen some sites say that to get the right cam that I need to know the weight of my car, rear gears, tranny gears, lifter type, heads, usage, etc. I'd really appreciate if someone could help me out as I seriously need the help.

 

Look at these.

 

I would consult with your tuner about if. If he is any good he should be able to get you the right cams. Bear in mind changing cams will require almost an entirely new valvetrain and all those parts must be taken into consideration as well.

 

Entirely right.

Schoolboy: I saw all 5 of these videos and they were very informative! Thank you very much! The only questions I still have is what makes blower cams different from NA cams and how do I know what I'm giving up since I can't have it all?

Ex. am I loosing mpg but getting more low end torque? Perhaps I'm loosing a steady idle for a longer duration of operating range? etc.

 

First, once you start looking at performance cams things like MPG should go out the window. A lot of people don't realize that once you modify your engine like this it is no longer going to run, act, or feel like stock. But that's what you want isn't it?

Anyway the main differences between things like blower cams and NA cams are the valve overlap and lsa. With a N/A cam you want more overlap to aid in scavenging. Which is when the outgoing exhaust gas helps to pull in the intake charge. With a blower cam you want very little overlap since the intake air is pressurized leaving the exhaust valve open simply blows boost out the back end.

LSA, or your lobe separation angle which is basically the amount of time in between both valves maximum lift , can affect your engine's dynamic compression if it's too small. That in turn will build more cylinder pressure which can cause detonation in a boosted engine since the pressurized intake charge is already raising it. However in N/A engines you want less LSA so that you can build cylinder pressure.

 

Thanks for this great question and information guys. This is a good topic for a tech sticky; "Everything you wanted to know about cams, but were afraid to ask." This has really expanded the vague concept I had of how a cam works to a better understanding.

 

How would I know what I'm giving up thought? I know that no cam can do it all so how do I know what I'm getting and what I'm loosing when compared to the stock cam that the car comes with? If you need a cam for reference I would use the CMS 2.5 blower cams since those are the ones that I like the most right now.

 

bump!

 

With any kind of stage 2 and above cam you are (usually) giving up your idle, it's certainly going to need to be re-tuned and adjusted. You are giving up some reliability and longevity since bigger cams put more stress on the parts. The cam specs should tell you it's intended operating range so it probably won't come alive until the minimum RPM listed.

You are also going to need valve reliefs in the pistons for a cam that big.

 

My block is completely forged so that should handle the stress right? What happens before the cam comes alive? Does the car run like crap? What are valve reliefs? What do they do?