This is a discussion on Cam Spectrum within the General Help forums, part of the LSx Technical Help Section category; Here is a decent visual of camshaft geometries and how they relate to mild-extreme. Often I see cam questions here ...
12-05-2005, 03:43 AM #1
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Here is a decent visual of camshaft geometries and how they relate to mild-extreme. Often I see cam questions here and this may be a good visual when choosing the best cam for you....
And from ol Konrad hinself.....good write up....educationj is good...it eliminates internet experts
Duration really plays a big factor in how the cam will drive and idle. The bigger the duration, the longer the valves stay open, and generally the 'lopier' and worse driving the cam will be. The numbers you'll usually see are the duration in degrees that the valve is open MORE than 0.050" of an inch. Cam cards will also list duration at 0 lift, and that will be a number like 270-290'ish. Cams that have the same duration for intake and exhaust are symmetrical, cams with more intake than exhaust are called "reverse split", and cams with more exhaust than intake are sometimes referred to as "traditional split".
LSA (Lobe Separation Angle):
Lobe Separation Angle, usually referred to as "LSA", is the angle of separation between the exhaust peak and intake peak. The lower the angle, the more the lobes will overlap, and that means more lope, gas smell, and drivability issues...however, the lower LSA can also mean more power and you get it sooner in the RPM range to boot. Duration and LSA are 2 very important items in clueing you into how a cam will idle and drive, although there is a LOT more to a cam than this.
Cam lift, in my opinion, is less of a complicated matter on these motors. There's not much of a reason to run less than 0.550" of valve lift, so anything between 0.550 and 0.600" is probably going to be fine. If you have ported heads, it may be best to lean towards cams with 0.570" lift and up as most ported heads will just keep flowing more and more as that valve lift increases. Note that a cam card will show lobe lift, which is the actual lift of the cam lobe. Once you take lobe lift and multiply it by the ratio of the rocker arm (stock is 1.7), you get valve lift.
The Lobe profile of a cam basically is the curve at which a valve is opened and closed. Some lobes are very EXTREME and will snap a valve open very quickly and then slam it shut, while others are "softer" and slowly open and close valves. The more extreme the lobe, the noisier your valvetrain will be and the harder it is on your valve springs...however, a more extreme lobe will generally idle better than a less extreme lobe with the same duration at 50 thousandths. If your cam has very aggressive lobes and your cam lift is up there, I'd suggest you try to lighten your valvetrain by getting titanium retainers if possible.
Choosing the cam for you:
For cars that need to stay stock sounding and driving, but still want a kick in the pants for horsepower, something between a 214 and 220'ish duration would probably be best. For the majority of the cars out there, anything in the 221-227 range is probably a better selection, and for the guys that want all they can get 228+ duration cam shafts are generally the minimum. As a novice all you can do is ask around, listen to cars, look at track/dyno results, and make your best guess. As long as you pick a cam close to what might fit you (i.e. mild, average, or extreme given the criteria above) you really can't go wrong. It's not a life or death decision here. A few degrees here and there isn't something to get your panties in a wad about....
Last edited by Sarge; 12-05-2005 at 03:47 AM.
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