I am still not getting what ICL is. Does advance make it any more lopey or rougher idle?

I understand how the valve to piston relation is. Advancing makes the valve get open quicker and further at TDC and retarding makes it open later after TDC.

Found this really helpful site, has pictures and everything. http://www.iskycams.com/degreeing.php

So that was a lot to read...Still, what does ICL stand for and does advancing make the car idle rougher?

 

icl=intake center line
advancing or retarding a cam should not make a noticable difference in idle.

 

on a CC306 the ICL is 108. the Exhaust Center Line is 116. add them together and divide by 2 to get the Lobe Seperation Angle and you get 112.

 

Ok, since that is now out of the way. How do you advance the cam? I was reading some articles and what not and it says to adjust the crankshaft gear so the rotation would be slightly off, making it advanced. Right or way off? Is there a specific way the advance has to be turned?

Just so everyone knows, I do not plan on doing this to my car, I just want to know.

EDIT: I think I got it now. Turning the crankshaft and sprocket to the left (counter clockwise) creates advance. Because when the cylinder is coming up, it is not in alignment with the camshaft, and the camshaft already began opening the valves before the crankshaft can get the piston to TDC. So here is another question, how many degrees is one gear slot? So if I rotated the crank sprocket 2 gear teeth counter clockwise, would that be 4* advance? Have there been any problems with stock bottom ends and valve to piston clearance with 4*?

 

Look at ICL like this. On a cam card, you have 4 numbers that have to do with valve opening. You have a Intake open (IVO), a Intake valve close (IVC), a exaust valve open (EVO), and a exaust close (EVC). When you determine your LSA, you get these 4 numbers. Now when you add advance in to the equation, you take those 4 numbers and shift them to open/ close sooner. All of the events move the same number. If you had a 13 IVO, a 51 IVC, a 57 EVO, and a 11 EVO with 0 advance, when you add 4 degrees of advance you would get 9 IVO, a 47 IVC, a 53 EVO, and a 7 EVC. Notice how the diffrence between all the events stayed exactly the same, but now open/close 4 degrees sooner. This is not to say that adding 4 degrees of advance will move your valve events 4 degrees, but it is a simple example.

On the other hand, Throwing your timing off by a tooth or 2 is not the way to advance a camshaft. Advance can be ground into the cam at the factory, then you line it up dot to dot like normal, or you can get an adjustable timing chain which has the nothches in the crank gear for a pre-determind amount of advance or retard that you may want.

 

Ok, I understand what the advance is now. I understood it before you posted, what I am saying or asking now is, is the advance set by the crank sprocket? I know it can be ground into the cam, I do not care about that. Here is what i want to know...

1: How many ways can advance be set or adjusted? So far what I know of is either grinding it into the cam, or rotating the crankshaft one way a bit. (I found an article showing the notches on a crankshaft sprocket)

2: Does advance cause detonation? I would think so, since the valves would be closed before the piston is at TDC. Unless it was ground into the cam.

 

1. Advance can be set by the 2 means you listed. Ground in at the factory, and adjustable sprockets.
2. Advance could cause detonation if your car wasn't tuned properly because you are adding more dynamic compression. The earlier you close the intake valve, the more dynamic compression you add. The detonation itself is caused by the compression though, which is made higher by the camshaft closing sooner. If you don't know what dynamic compression is, I could hit on that if needed.

 

Ya can't move a LT1 cam with the sprockets unless ya want to get the timing and injector firing in the computer re done.