JUN Releases Camshafts for the 1NZ-FE

[sleey0]

Garm so rods and pistons is really like the meat and potatoes if u want to increas the engines capabilities?

[severous01]

Originally Posted by sleey0

Garm so rods and pistons is really like the meat and potatoes if u want to increas the engines capabilities?

if you think about it like this... you'll understand:

the pistons and crank are the legs and arms....the workers and get stuff done. the intake and exhaust is the mouth and butt...taking in and letting it all out. and then the brains behind all the operation...how much air is taken in, how much air is let out...is the cam.

Valve Lift- Well this is the easy one, The distance that the lobe of the cam lifts the tappet multiplied by the rocker arm ratio determines the valve lift. Everyone knows this one!

Duration- The time in which the valve is off the seat during tappet lift, measured in CRANKSHAFT degrees. As there has to be some point in which you begin to measure the lift of a cam there are usually two figures given on a spec card. The Advertised Duration and the Duration at some arbitrarily chosen point (Usually .050" lift) Some manufacturers use a different amount of lift and this can cause confusion Most Cam manufacturers use the .050" figure, but it is wise to be sure when comparing different grinds. When checking a cam you should always check it at the tappet rather than the valve because of minor variations due to lash, and rocker arm ratio.

Centerline- The Centerline of a Cam is the actual position or phasing of the cam in relation to the Crankshaft. To wit: The position of the center line of the #1 INTAKE Lobe of the cam in relation to the position of the #1 Piston measured in Crankshaft degrees of rotation AFTER TDC. This is the figure that is used when we talk about 'Degreeing " a cam.

Lobe Separation - This is the PHYSICAL configuration of the cam in relation to the actual spacing of the intake and exhaust lobes from each other. Lobe separation is ground into the camshaft. You CANNOT change it (Unless you reground the cam). You CAN change the Centerline by degreeing. These two terms are often confused with each other.

Base Circle - This is the lowest part of the cam lobe also referred to sometimes as the "Heel" of the cam. This is the fully closed position of the valve. This is also where you should make your valve adjustments. If you adjust your valve lash at any other point on the cam, you will have problems. We will discuss the proper way to adjust your valves later on.

Some stroker motors require the use of a "Reduced Base Circle cam" in order to clear the rods. These cams are ground with a smaller base diameter and require some specialized components such as longer pushrods.

Symmetrical - A cam that is Symmetrical has both sides of the cam lobe exactly the same. In other words, the intake ramp of the cam lobe that accelerates the lifter to actuate the valve has the same shape as the portion of the ramp on the downside of the lobe that lowers the lifter. These designs are very easy on the valvetrain as it is a smooth transition from open to closed.

Asymmetrical - An Asymmetrical cam has opening and closing ramps that are unlike and unequal. This profiles usually found on high performance cams and offers a high velocity opening and a lower velocity closing ramp in order to snap the valve open quickly and then set it back down more gently.

Dual Pattern - Again, a grind that is usually found in a high performance cam. The Intake lobe configuration is different from the exhaust lobe. Usually the exhaust lobe is ground with slightly more duration that the intake lobe. Small block Chevy engines really like more duration on the exhaust in most cases. A single pattern cam (Both lobes giving the same amount of duration) work well in street engines.

Cam Walk - A phenomenon that occurs with Roller cams due to slight inaccuracies in the lifter bore spacing. Most Roller cams use a cam button to control the tendency of the cam to unscrew itself from the block. Bushing the lifter bores can control this problem but is very expensive. A cam button will work quite well in 90% of cases.