Degreeing a cam in the age of CNC?

[TomH]

Given the precision of today's CNC technologies, does it make sense to go through the effort of degreeing a cam? This question pertains to "off-the-shelf" grinds from top tier suppliers like Comp Cams, Lunati, etc.? Unless you are going with a custom grind, has science overtaken art to the point where this can be considered an obsolete practice?

Whaduya think?

[George Snyder]

I am pretty sure that most people, just align the marks when installing and leave it at that.
Some timing chain gears have three marks. 4 degrees advanced, dead on, and 4 degrees retarded. So even if you want to make minor adjustments it's fairly simple.
Bud

[Hotfingrs]

George, you're right most people do just align the marks, when putting in a new cam. I for one would never put in a new cam without degreeing it first to make sure of the specs. Also you need to know that everything in your engine is also on the money, you can't equate new with being dead on accurate. I also plug the engine and cams spec into a couple of different computer programs to see what advancing the cam will do to power and torque. My last cam was installed at 4 degrees advanced, and I just picked up my new engine and this cam is intalled 2 degrees advanced. Depends on what your looking for out of your engine.

[A Snake]

Another way to look at it is that while the cam may be perfect, the rest of the engine may not be.

If it is done right, degreeing the cam assures that all of the variables in valve train geometry as well as crankshaft/camshaft relationships have been accounted for.

Al

[Jmar]

I think if you have the main bearing caps align-honed, the crank has been moved slightly toward the cam. This would change the relationship between the two and may slightly alter the cam timing.

I degreed mine to check and make sure that I had the correct cam and double-checked the piston/valve clearance since I was using higher ratio rockers. I didn't alter the timing although my cam appeared to be 1 degree retarded.

I felt a little smarter knowing that I learnd to degree a cam too!

[ted]

Because of all the manufacturing tolerances in the various spots of an engine to which the camshaft timing is related, it's a pure neccesity to degree in any camshaft being installed.

These variances include:
1) The location of the crankshaft key way.
2) The location of the crankshaft gear key slot.
3) The location of the camshaft dowel pin.
4) The location of the camshaft gear dowel pin hole.
5) The cam to crankshaft center to center distance.
6) The gear set center to center distance.

If any one of these are off, then the camshaft timing will be altered. If per chance, several are off in the same direction, either positive or negative, then the amount of error will be "stacked up" or increased by the sheer addition of the amounts of error. Hence the need to actually check the camshaft phasing versus just lining up the marks.

For those engines that have been alligned honed, timing sets are available in various shorter amounts to compensate for the reduced center to center distances in the block that resulted.

And here's another one. The next time you're degreeing in your camshaft, check every cylinder, not just number one. You may be in for a shock depending upon the cam manufacturer.

[Mr.Fixit]

Must do it, Just last year got a bunch of cams that were 6 degrees off. It happens.

[ccomt]

When degreeing a cam, aren't you just checking the relationship between the cam shaft gear and the lobe for the #1 cylinder intake valve? I don't mean to minimize the importance of that, but does anybody go through the effort to check the timing for every single lobe? Isn't it just as likely that any of the other lobes could be off. To really be accurate and make sure all of the lobes were done properly, I would think you need to check them all to make sure that the cam was ground correctly.

Just my $.02

(Sorry Ted. I see you've already got it covered!)