[thumper78]

I'm becoming very frustrated with this.

I'm trying to degree in a cam. Found TDC with a piston stop and a dial mounted to the crank snout. Adjusted the pointer to be at TDC. Checked TDC again, everything checks out.

Dial indicator is set on deck using one of the head bolt holes and a 1/2" bolt. Every joint is a solid adjustment with a lock bolt, not those wimpy clamp bolts that you see on the adjustable linkages for holding indicators to a magnetic base. My measurement is taken off a lifter that I modified with a pressed in extension to reach the indicator. The lifter is essentially a solid rod now. This way, I'm able to get a straight motion into the indicator. I seriously doubt that this indicator is moving.

I then set the crank and sprocket gear straight up. Used the measure .050" down on both ramps method to determine the intake centerline. Set indicator to 0 at top of lobe, rotate crank CCW beyond .100 on the intake opening ramp, come back up CW to .050 and record the degree reading. Then rotate over the top of the lobe CW and down to .050. Record this number. Add the 2 numbers together and divide by 2. Simple enough.

Came up with 108* . Not bad, but 2 * off from cam card. Comp Cam wants 106*. I figure I can get it better with the other keyways in the crank gear.

So I set it at advanced position (-4*). Now the centerline is 100* I thought that moving the crank gear 4* moved the cam 2*, not 8* Or is it the other way around.

Tried the other position (retard, +4*), and the centerline is now at 116*.

I even tried moving the chain a tooth both ways on the cam sprocket. I still couldn't get it to come up at 106*

Can the keyways be that far off?

Or is my thinking of cam gear to crank gear relationship that far off?

BTW, I tried this a few months ago with the same results. I guess that if it smells like s**t, looks like s**t, , then it must be s**t.

Think I'm going to get some offset cam keys and do this the old fashion way.

Any insight from the sages out there.

[lust4speed]

Removed in the interest of not confusing anyone. I had it dead-backwards. I'll go over and sit in the corner now...

[6t7gto]

from the comp cam site:
Keep in mind that to advance the cam, you must lower the intake centerline.
For example, if our cam has a lobe separation of 110 degrees, the
cam is “straight up” when the intake centerline is 110 degrees. Moving
the centerline to 106 degrees advances the can 4 degrees. If we change
the centerline to 112 degrees, this would be 2 degrees retarded.

from thumper's post:
Came up with 108* . Not bad, but 2 * off from cam card. Comp Cam wants 106*.

therefore your cam is retarded.
i would check and double check.
make sure the dial indicator is straight with the lifter.
my cam called for 106*. i came up with 107*.
moved the crank sprocket 2* and i got 104*. WTF???
checked and double checked.
went back to straight up and got 107* again.
put crank sprocket at 2* advanced, again, and finally came up with 105.5*.
left it there and car is running just fine.
i think my indicator wasn't close enough to being inline with the lifter travel.

david

[Motor Daddy]

Are you using the appropriate crank gear timing mark for the corresponding keyway? If it's a 3 keyway timing set, there are three keyways and three timing marks on the crank gear.

And yes, a ICL of 108 is 2 degrees retarded from a 106 ICL. When you are speaking in crank degrees (as you are when the cam is installed), and you are checking ICL, using the +4 keyway and timing mark on the timing set advances the cam 4 CRANK DEGREES on top of what is already ground in the cam. If the cam had 4 degrees advance ground in, and you use the +4 keyway and mark, the cam is actually 8 degrees advanced from "straight up". Since a 106 ICL means 106 crank degrees AFTER TDC, advancing the cam in relation to the crank means the ICL occurs closer to TDC, which means less degrees AFTER TDC, which means a smaller number. Is that confusing enough for ya?

[lust4speed]

Okay, did some reading while sitting in the corner. Crane cams has an intersting take on setting up a cam and it seems to make sense:

"If your cam card does not show the opening and closing at .050” lift (All Crane and cam Dynamics cam cards do!) thenyou must use the intake centerline method to degree your cam.We believe that degreeing the cam using the opening and closing at .050” lift is much more accurate. The problem with the centerline method is it has you finding the theoretical centerline of the intake and/or exhaust lobe. It makes the assumption that the lobe you are checking is symmetrical, with its opening side being the exact same shape as the closing side of the lobe. Most modern cam lobes are asymmetrical, with the opening side of the lobe being much more aggressive and the closing side being more gentle. Therefore when you attempt to locate the middle
(or centerline) of the asymmetrical lobe there is an automatic error. It could be as little as 2° or as much as 6° depending on the actual lobe design. Since the opening and closing at .050” lift method is not affected by the lobe design, we believe it is more accurate to degree this way."

Seems like a very good idea to set the cam to where you want the intake opening at .050" to be and then just check the centerline to see how close it is.

[thumper78]

OK MD

You mean I'm not supposed to use the Triangle mark when I have the crank gear installed on the keyway with the square next to it!!
Anyways, under all that double talk, I think you answered what my real question was. Are you a lawyer in the real world?

As I understand it now, if I use either of the 4* degree slots, then my cam ICL should move 4* also.

Not 2* and definately not 8*

And 6t7, I only checked my readings maybe a dozen times. But it always came up the same. One needs to stop somewhere, and reevaluate things. I'd wager that my indicator mount is pretty solid and my indicator travels in a nice straight line with the lifter and the extension, as I stated in my original post.

And LFS, I saw your first post before you edited it, and I agree that 108* should be close enough. I was just playing around with the different keyways and was bothered by coming up with an 8* difference in either direction when I changed the crank sprocket. If it was 10* in one direction and 6* in the other, then I would agree that I have an issue with my indicator setup as suggested by 6t7. I just find it odd that both errors are off the same amount in each direction. And I got the same results when I first tried this over a month ago. So this discrepency makes me question my straight up result.

Guess I should check the accuracy of the keyways. I'll update my findings at a future date.