Can someone please explain the differnence in cams for.. ie.. 264 270 280... what do those numbers mean. I'm not very familiar with cams and how the work... I', more ofa bolt on kinda guy lol.. THanks...

 

those numbers are degrees of duration, in other words the period of time in which the valve will be open. a greater duration will cause the valve to be open longer, which also increases valve overlap (period of time in which intake and exhaust valves are both open) in general terms, the increase in duration and valve overlap will give you better top end power while sacrificing some of the low rpm torque.

 

so for a street car application 272 would be best?

 

264 would be best for street, 272 is OK but lot of people drive with those in the street with no or lil problems.

 

If you want drivability then go for 264, they have the best idle. 272s have a more lumpy idle but can be fixed with tunning and gears.

 

Thats good info.

 

If I can ask a question. What are cam gears exactly and how do they work?

 

cam gears are toothed sprockets connected to the cams so that they can be driven by the crankshaft and increase their rpm in conjunction with the crank. you'll hear terms such as degreeing the cams or adjustable cam gears, this has to do with timing which is another story.


not to sound negative but i think it would be a good idea for you to get a little more of the basics down pat before you start modding your evo.

 

hes like a cam dictionary. lol just basicallly go through the forum, youll find anything you need. i know im learning slow lol.

 

advertised durations are measurements of crankshaft degrees(usually based on 1m lift with jap. cams [.039"]and .050" with american cams[sometimes .020"])duration numbers are given at a certain valve lift so that duration numbers wont be distorted by the lack of lift when the valve is seated
note: although greater lift increases power,we are limited by our port as it can only flow so much and after that horsepower is not increased and valvetrain noise and wear are increased as well as damage to valve guides

 

cam gears are for advancing or retarding the valve openings
advancing the cams baically closes the intake valve earlier and increases compression(dynamic) at lower speeds when airflow isnt pushed by momentum therefor yeilding more torque
retarding the cams closes the intake valve later allowing more airflow to fill the cylinders at higher rpms when air is flowing hard due to momentum,increasing hp at high rpm and decreasing lower end power and creating rough idle because at lower rpm the longer lift is scavenging for air due to the lack of airspeed in wich it was designed/adjusted for