Originally Posted by EDXR8
Okay basically, lift is how much the cam opens the valve, the greater that is ttechnically the more flow ther is (Windsor cams usually range from 0.450" to 0.550"). Duration is how long the valve stays open in degrees, normally it is given as duration at 0.050" lift. Anything over about 220 duration @ 0.050" usually reduces idle quality. Lobe seperation angle (LSA) is the seperation of exhaust and inlet centrelines. 110LSA will normally give a rough idle, 112 is better, 114+ is close to stock. There are plenty of other factors but they are the main ones. If you look at the cam specs, most companied give a description of idle and power band as well.
The 2030 and 2031 cams can be run on auto or manual cars as they have good idle (lumpier than stock though) and good low rpm behavior. The 2031 has a slightly better idle so will be slightly better for autos. Power range from memory is around 2000-5500rpm on both cams but you will probably notice that the cam really starts working at around 3000rpm through to redline.
I thought the gross lifts for the cams were more in twenties? For instance stock lifts for various models :
289 in/ex 0.2303/0.368
HP 289 0.2983/0.2983
302 68-75 0.2303/0.2375
302 76-79 0.2373/0.2474
302 80 0.2346/0.2446
Boss 302 0.290/0.290
351W 69-75 0.260/0.278
351W 76 - 80 0.260/0.260
351W HO and cop 0.278/0.283
Net lift after a 1:1.6 rocker ratio is probably what you were talking about?
FordFan86 you should really find a book, but here is a short run down:
Duration is the number of crank degress the valve is open. There are two figures generally quoted: "advertised" and "@0.50". The advertsised is supposed to be the actual valve operating range, while the 0.50" (or @ 50) is a standard that allows comparison between cams. On windsor hydraulic lifters the cam events are generally taken at 0.006"; on engines with valve lash the duration is taken from whatever that lash is. As you increase duration you push the peaking torque up through the rev range.
Lobe seperation angle (LSA) is the angle formed between the centrelines of the exhaust cam and the intake cam. As you increase the LSA you get better idle, better vacuum, a wider power band, less peak power, flatter torque curve. If you close the angle (more overlap) the torque will be peaky and earlier, rougher idle, strong midrange torque, less vacuum, etc
Centrelines help you determine the intake offset in relation to the exhaust. This allows you to work out valve events in relation to piston velocities and position. Advancing the intake in relation to the exhaust makes the power peak earlier.
Overlap is the when the exhaust valve and intake valve are both open. Increasing overlap moves the power band up through the revs and makes the torque curve peaky.
Lift the amount of opening. It is the height of the nose from the base circle of the cam. When people talk lift they generally talk net lift which is at the valve after deducting lash gaps. There is not much point in increasing lift unless you intend running at high revs. Unless you don't mind the probability of changing spring retainers, reworking valve guides, stronger springs and dampeners, increase lobe wear, coil bind, etc because of greater speed and acceleration in valve movement plus steeper ramp and flank angles you will probably also increase duration. If you have a narrow LSA, increased lift risks piston interference.
Howzat for starters?