What does centerline mean?

[charger1970]

What does the centerline on a camshaft do for the performance of an engine?

[383-man]

It means the point of maxium lift on the intake lobe in relation to crank degrees. Its usually checked on the #1 cyl and it has an effect on performance as to when the valves open and closes in relation to crankshaft posistion! Ron

[charger1970]

So does that mean more HP or Tourqe or what?

[383-man]

Yes and no as it depends on the setup as to where the cam timing works best ! It can mean more hp and torque but it may be set more for bottom end or top end as it moves the powerband to different rpm ranges so it depends on your complete setup as to where it works best! One cam may work better at a different setting in a heavy car with alot of gear and convertor then where it may work in a light car with less gear! Ron

[Jims451]

Do you mean Centerline as related to the cams lobe seperation angle, or centerline as related to the cams installed position relative to crankshaft rotation?
I know these two are often confused because the numbers look simular and are related in a inderect way, but they mean completly different things and are even measured differently.

First, Lobe seperation angle is measured in camshaft degrees, not crankshaft degrees, and it is the angle between the center of the exhaust lobe and the center of the intake lobe on the cam.
The Lobe Seperation Angle or LSA for short, directly affects the amount of overlap a cam has and inderectly affects the shape of the torque curve.

To "centerline" a cam as related to degreeing in the cam means to install the cam so the valve events are syncronized with the crankshaft position.
The reason the LSA number is simular to the installed centerline number is simple math related to the fact that the crankshaft turns twice for every one revolution of the cam.
Or if you installed a cam on the same centerline as the cams LSA, then the cam would be half way between the exhaust and intake lobes (center of overlap) when the piston is at TDC.
Since centerlining a cam to crank position is usually done only on one cam lobe at a time, the standard method of degreeing a cam is to find the center of the intake lobe and verify that it is located at the LSA number (assuming it is installed straight up.)
Remember that since this measurement is taken in crankshaft degrees it will be twice the value of the degrees at the cam. An example would be a cam with a 108 LSA. The Center of overlap is half that number or 54 degrees. To Cenerline the cam so the center point occurs at TDC, the crankshaft has to be at 54 degreex x 2 (or 108 degrees) when the intake lobe is centered under the lifter.

The LSA is ground into the cam and it can not be changed, but you can change the installed position of the cam be advancing or retarding the cam in relation to crankshaft position. This just changes the valve events a few degrees which can move the power curve up or down the RPM range by a few hundred RPM. If you think you need to move the RPM range more than a few hundred RPM, then you really need a different duration camshaft.

[charger1970]

I was looking at a stock cam for a 383. The lift is 450 and the duration is 268 and the centerline is 115. It seems that the higher the lift the cam has the lower the centerline is. I thought that 115 centerline on a stock 383 cam meant that it would produce a lot of tourqe.