Maybe a silly question but I'm looking for an answer. What does 264 or 272 number means on the camshaft? Also what is the dimension of the stock one in the EVO?

 

The 264 or 272 refers to the lift duration (out of 360 degrees). So a 264 cam is actually exerting a lifting force on the valve for 264 degrees out of 360 degrees complete rotation.

So the bigger the number, the longer the valves stay open.

Note that all 264 (or 272) cams are not alike. In addition to lift duration, lift height is important -- how "wide" the valve is opened. High-lift cams generally give more power.

 

It refers to the degrees of roatation that the valve is open.

Keith

 

How is the lift duration represented?
Also what are the specs of the stock cam?

 

Not sure what you mean by the first question, however, the stock cams have a duration of
256 (intake) and 252 (exhaust). The lift is not specified in the tech reference manual.
This is also a number based on when the valves start to open and when they are shut again.
Some cam mfgs. spec the duration from different points, say, from 5% after opening to 5% before it closes.
So not all cams with the same quoted number are the same.
Also, as it was stated, the lift is important, as well as how fast the valve opens.
For instance, the HKS 264 cams will work fine with your stock valve springs. But the JUN 264 cams won't.
They have faster opening rates, so your valves will "float" at a lower rpm.
( BTW, floating means that they will literally bounce off the valve seats before closing completely, so you need
stronger springs to prevent that.)

Please give me more on what you mean by represented ...

 

Actually high ramp rates mean it will float at high rpm.
The cams are engineered such that the valves won't hit the piston, but this assumes that your valve springs will keep the valve in motion with the cam lobe so that they both are running the same amount of duration, etc. At high rpms, the high ramp rate "closes" faster than the spring can close the valve. When this happens, the valve is not longer in motion with the cam and it can hang open long enough to hit the piston. Even before it hits the piston, it's still slamming onto the valve seat too hard. In some vehicles, very stiff springs will keep the valves from floating but they will still slam the valves shut too hard. That is why ramp rates are important to consider.
Valve float is one primary thing that will normally limit a well balanced motor (like the 4G64) in it's ultimate rpm limit.
A good way to compare the actual performance of a cam, more than total duration, is duration at a specified lift. This will tell you how fast it is actually opening and flowing air, not just coming off the seat. A lazy cam can crack the valve open (off the seat) and sit there for quite a while before making some decent lift. The same thing on the closing side. These cams will be easier to work with on the stock valvetrain (HKS). Cams that are more aggressive will try to open them up fast and close them fast to make the most of the total lift (JUN). These types of cams can have more of the airflow right from the beginning and right up to the last second to take advantage of certain things.

Mark
www.Quantum-Racing.com

 

another question?? What is the advertised lift of the 264 and the 272 cams from hks @.050 lift compared to the works cams....

 

Duration is usually represented at .050 lift.
Your question is kind of confusing. Lift is lift, it is how much the valve is opened. It really has no relative point like the .050 to start. Sorry I don't know the specs off-hand but they are out there on this site in more than one place.

My question to anyone who may know is, do companies like HKS measure thier duration@.050 lift? Just about every US manufacturer uses this as a standard. This starting point is the only way to accurately advertise lift. Otherwise you are going from when the valve first moves and that is much harder to pinpoint for a starting point. I just don't know if everyone uses this standard, particularly Evo cam manufacturers. (Obviously)

 

HKS cams use 10.8 MM lift intake and 10.2 MM lift for exhaust. Stock lift is 10.00 MM intake and 10.00 MM exhaust

 

Yeah it kind of was wasn't it.. I was actually asking for the lift and then the advertised duration @ .050 but I typed that as I was going to bed and messed up...Sorry...

 

Thanks for the reply... Is that for the hks or the works b/c I read peoples comments sometimes that they works has the same duration but more lift...

 

Has anyone passed emissions with either of these cams?

 

I'd also like to know if anyone has passed emissions with either of these cams in California.... plus other Mods you've had done to your Evo

 

It seems like the specs for cams for imports are pretty sketchy in general. I find this very frustrating coming from the American V8 world where you can get advertised duration, duration at .050 lift, duration at .200 lift, lobe separation angle, lobe center angle, degrees of advance ground into the cam, etc. It's also a big problem with assessing valvespring suitability. For example, how much lift is possible with the stock valvesprings before you hit coilbind?

For things like cam swaps, I really like to know all the details to make sure that the parts will work together okay. Just because some shop stuck in a certain cam and the car held together and ran a good time at the strip doesn't mean the valvesprings aren't going to become heavily fatigued in 5K miles or that the set-up isn't on the verge of coilbind.

Also, has anyone flowed Evo heads? How are you supposed to decide what sort of lift is appropriate when you don't know the flow characteristics of the heads?

And how analogous are the results obtained on DSMs to Evos? I've heard that the heads are quite different.

Argh...so many questions, so little available information.