2QUIK6

I've seen this before on automotive shows using some tool with degrees on it, but never explained why?
What more is there to do if you raise the #1 piston to TDC, the crack timing chain sprocket should have its "dot" at the 12:00 position, when install the cam and cam sprocket and rotate till the cam sprocket "dot" is at the 6:00 position and slap on the chain??
Thanks


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jcb999

the following url helps explain it some. but, in a nutshell, it's just the process of making sure that the intake valve reaches it max lift at the point (relative to piston location) that the manufacturer intended. And changing it if it does not. It involves using a dial indicator to find where max lift occurs (when you have the cam installed using the dots)

http://www.compcams.com/valvtim1.html

We have now passed through overlap. The exhaust valve has closed just after the piston started down and the intake valve is opening very quickly. This is called the intake stroke (figure 3), where the engine "breathes" and fills itself with another charge of fresh air/fuel mixture. The intake valve reaches its maximum lift at some defined point (usually about 106 degrees) after top dead center. This is called the intake centerline, which refers to where the cam has been installed in the engine in relation to the crankshaft. This is commonly called "degreeing". We will talk about this later also.



[This message has been edited by jcb999 (edited August 08, 2001).]

2QUIK6

Ok, I think I see. Using a degreeing tool is a way to advance the lobe center X number of degrees for different purposes, higher end torque, lower end torque, etc....
But if your crank shaft sprocket has several keyways and they are marked how many degrees it advances, I see no need for the degreeing tool if you use one of the already cutout keyways correct??
And in my case, I want to set it at 0 as normally would be the case, so I really don't need to do that if I follow the steps I listed above, correct?
Thanks

jcb999

well, yes and no. It is not likely that the dot on the crank gear is stamped incorrectly, but, the process of degreeing a NEW cam assumes that you have not confirmed that the manufacturer did not make a mistake during the grinding process and you go through the process of ensuring the cam is gound correctly (according to the cam card). After you have determined it is ground correctly, the you use the degree wheel (or advance/retard keyways on the crank gear), to move the powerband around.

Think of it like you degree a new cam but you change the installed intake centerline on a previously installed cam. You almost certainly need a wheel for the first process but not necessarly the second.

[This message has been edited by jcb999 (edited August 08, 2001).]

AJ_92RS

The main reason that you want to check the specs of a cam is that sometimes the cam is not what the card says it is. Cam companies make mistakes just like we do.

Advancing the IVO in relation to crankshaft position is not degreeing a cam. It is called advancing the cam. Even if you retard the cam from the cam company's specs, the cam is still advanced, but just not as much. For a cam to be truly "retarded", is must be set BTDC, and that would be one funny running engine.

What you are referring to is the Intake Centerline and what it is set at in relation to the position of the crank. An optimum range for street use would be anywhere from 100-112 deg. ATDC. But that also depends on the cam design, LSA, duration, & lift. Just remember that the more you retard the cam, the higher the "usable" RPM range (ie. higher HP). The more you advance it, the lower the "usable" RPM range(more torque).

Hope this helps,
AJ