Sorry if this has me come as being a total newb, but I have no idea what in the world Cam's do or how they help the EVO and why it's such a popular mod on the EVO's.

Could someone please breakdown what they do, and how the different ones matter or help and by that I mean the 272, 264, or 280's. I honestly don't know anything about them and would like to learn. I've searched but haven't found a thread this basic at all. I keep seeing info about the lift, lobe and whether or not the valve springs and etc need to be upgraded, but none makes sense yet. Help would be much appreciated.

Thanks.

 

Just got to search harder . But here, instead of flaming, this thread has alot of good info.

https://www.evolutionm.net/forums/showthread.php?t=240508

 

Sorry, I was just searching in the Newb/FAQ forums...I appreciate it though

 

hoped that link helped

 

Going through it now, still haven't ran across anything that talks about lift/lope/and dialing in numbers with your cams...something about running them +2/+2 and etc...

 

If you don't know what valves are and how they work in your engine you will need to visit the site "How stuff works" before reading this article. This article will presented to the BEST of my knowledge and will likely have some errors in it so bare with me :P


What cams Do:
They lift valves which in turn let air through the intake into your combustion camber or another set of valves will let exhaust gases out. These valves are the intake and exhaust valves respectively and are run by two separate cams.


Cam basics

Duration:
Cams have a tear shape which allows them to lift and close the valves for a set duration. It is important to note that cams spin at HALF the speed of the motor. This simply means that any amount of duration you give a camshaft is effectively doubled.

This picture will help me illustrate some basic principles:


As you can see by this picture the cam has a lobe of 108 degrees. But because the cams spins at half the speed of the engine its effective duration is 216 degrees. This is a pretty mild lobe for most cars. 272 cams would mean the duration is 136 degrees on the actual cam. thats closer to the cam profile below.

Lift:
The lift of the cam is shown in this picture


This lift would be multiplied by rocker arms if we used any. The evo motor as i know it just uses taplets which directly correlate with the lobe height. Obviously increasing the lift can increase the flow of air but only to a certain point.

 

Ok that somewhat makes sense...Now then what about all this business of dialing in on cams? About running them 0/0 or +2/+2 and etc?

Again, I really appreciate the help!

 

That basically means your changing the timing of the cams. That moves when the cam lifts the valves in respect to the engines movement with the piston. the +2/-2 would be like +2 timing on the intake cam and -2 degrees on the exhaust or visa versa..

This is used to "move around" the power band of the cam to a desired location. Buschur has showed that the stock timing of the cam is pretty good and you can read plenty of articles on this. There is much debate on whats needed and whats not.

Suffice to say a few extra bhp can be had at the top end with some minor tweaks. OR if you have very aggressive cams you can tune the lopey idle of the cam down a bit.

 

Can the stock gears be tuned or do aftermarket ones need to be purchased for this added luxury of being to tune the cams?

 

Adjustable cam gears are required yes.

Sometimes the screws loosen up and fall off so be sure to locktite them.

 

But again, this added adjustment via Cam's isn't always necessary is it?

 

More often than not no it isn't.

As graphs have shown me at least the timing adjustments on the cams sacrifice the total benefit of the cams profile for a smaller area (usually peak horsepower). Personally the broader the power band the better IMHO.

 

That's probably what I woudl want too...


So broader power means quicker spool up and much more torque but at a loss of top end correct?

And slower spool up less tq but at a gain of top end correct? (264/264 cams?)

And these in between ones 272/272 cams?

These are the two scenarios when it comes to cams? (280/280 cams?)

 

Search for buschurs testing on cams and you'll see what i mean. You need to do some reading and decide whats best for you.

 

any others want to chime in?