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Degreeing Cam - Dot to Dot!
https://www.slantsix.org/forum/viewtopic.php?t=16918		 Page 3 of 3
Author:  Doctor Dodge [ Tue Jun 20, 2006 10:45 pm ]
Post subject:  Re: Degreeing Cam - Dot to Dot!
Quote:
So a new cam out of the box will need the cam drive gear drilled for offset cam bushings in order to degree the cam and put exactly on the intake centerline. Right?
Set everything up and check the cam timing, sometimes it ends up where you want it, right out of the box and life is good. Other times, it is to far off and needs to be adjusted,... that is when you have to drill-out the cam gear hole and move the cam in relationship to the top gear. (or get a multi keyway bottom gear that allows adjustment)

Quote:
How are the offset bushings held in? The cam bolt/washer assembly holds in the cam, tightening against what?
bwhitejr
The washer covers the bushing and holds it in place.
Truth is that I stopped using off-set bushings years ago. If the cam timing is off, I work-out which direction and how much I need to move the cam and take the top gear over to the mill and "elongate" the pin hole. (make it into an oval hole) I stick a shim into the empty space left over and trap the shim in there with the cam gear retaining bolt and washer.

Funny how I spent many hours learning how to degree-in a cam but after you have done a few, (and have the tools) it only takes 15 -20 minutes to do one, including making any needed adjustments.
DD
http://www.dutra.org/pictures/engine/pa ... in-set.jpg
Author:  Dart270 [ Wed Jun 21, 2006 6:16 am ]
Post subject: 
I haven't bothered with the bushings either. Last one I did I used a piece of flattened brake hardline as a shim as Doc described. :shock:

Lou
Author:  slantzilla [ Wed Jun 21, 2006 7:46 am ]
Post subject: 
I use the bushings, but have noticed that they do not always move the cam as much as they are stamped. :shock:

I had an MP double roller chain that was stamped 3 teeth retarded on the cam gear. Man, did I have to drill a big slot for that one. :roll:
Author:  AndyZ [ Wed Jun 21, 2006 8:35 am ]
Post subject:  Re: Degreeing Cam - Dot to Dot!
Quote:
So a new cam out of the box will need the cam drive gear drilled for offset cam bushings in order to degree the cam and put exactly on the intake centerline. Right?

How are the offset bushings held in? The cam bolt/washer assembly holds in the cam, tightening against what?

bwhitejr
They use an offset hole in a round slug. The slug fits into the cam gear hole and the of-center hole fits over the cam pin. These "slugs" come in different offsets; 2*, 3* 4* etc. Like the big blocks Mopars if you are familiar with those.
Author:  AnotherSix [ Wed Jun 21, 2006 11:18 am ]
Post subject: 
While you are degreeing the cam you might as well make sure your ignition timing mark is really at TDC. Alot of them are off too. When you are dialing it in and it "seems" to want more or less initial timing and more or less total than it should, it's nice to know where you really are. It's even easier than degreeing the cam and just having a center punch or notch filed in the right place can make such a difference.
Author:  bwhitejr [ Wed Jun 28, 2006 4:55 am ]
Post subject:  Degreeing Cam - Dot to Dot!
Got out my original cam and sprocket gears and did some measuring. The stock cam sprocket is 6" in diameter, has 38 teeth and the pin location relative to the DOT appears to be 133*. The original crank gear is 3" in diameter, has 19 teeth and the keyway relative to the DOT appears to be 45*.

In comparison to the Cloyes double roller crank gear (S339) and the Cloyes cam sprocket (S338). Here are the results Cloyes crank gear has 25 teeth and the keyway to DOT appears to be 45*. The Cloyes cam sprocket is 6.23" in diameter, has 50 teeth and the pin location relative to the DOT appears to be 133* just like the original. So it appears that the Cloyes double roller timing set keeps the same relationship between the crank and the cam.

So any error in cam timing (outside of normal production tolerances)MUST come from the cam grinder who is inaccurately locating the pin relative to the intake cam lobe.

From reading other related posts on this site, should I assume that cam manufacturers are sloppy about pin location?

How could that be in this day of computer controlled manufacture?

bwhitejr
Author:  SlantSixDan [ Wed Jun 28, 2006 7:25 am ]
Post subject:  Re: Degreeing Cam - Dot to Dot!
Quote:
From reading other related posts on this site, should I assume that cam manufacturers are sloppy about pin location? How could that be in this day of computer controlled manufacture?
It is an error to think that computer-controlled engineering, design and/or manufacture is necessarily more precise, accurate or consistent than pre-computer operations. Computers are just tools, like hammers and screwdrivers and wrenches and grease guns and chisels: when they are configured and maintained correctly and used skillfully, thoughtfully and properly, the results are often constructive and good. When they are improperly configured or maintained, used in an ignorant or careless or thoughtless manner, the results are usually destructive and bad and faulty. The computer is only as good as its programmer and operator.

I notice your cam is from Comp. I'll add your experience to my already-lengthy list of reasons never to buy a cam from them for a slant-6. (highlights of the other items on that list: Improperly-located oil passages, oil passages left undrilled or incompletely drilled, unrealistic lash specs that cause running problems, Chevrolet lobe profiles pawned off as Mopar cams...)
Author:  bwhitejr [ Wed Jun 28, 2006 9:05 am ]
Post subject:  Degreeing Cam - Dot to Dot!
I am not saying that there is anything wrong with the cam. But I was expecting more power than I am getting especially in the lower range. After all this is a truck!

Maybe just a little more advance on the distro will do it.

I guess I am just disturbed by the prospect that the cam could be off timing when out-of-the-box it should be correct. :(

Especially since I gave the machinist the cam card to set it up and when I asked him if he degreed the cam he said yes. "It is set up at 111*". I said the lobe separation is supposed to be 110*, the intake centerline is at 106*. He just shrugged. I have pictures of the cam installed. And it is clearly visible that the cam pin hole is in the stock 1/4" hole being held in by the cam washer.

bwhitejr
Author:  bwhitejr [ Mon Oct 30, 2006 3:52 am ]
Post subject:  Degreeing Cam - Dot to Dot!
OK, I am slow, it takes a while for this to sink in, but when you install a cam in the dot-to-dot alignment you are basically setting it up on the intake lobe which is 110* from the exhaust lobe (assuming lobe separation angle = 110*). So if you want to set up the cam for the suggested install which in this case is 106*, you have to degree the cam and advance it 4*. Either with cam bushings or timing sets that give you 4* advance.

Have I finally got it now, or am I off again. :?

bwhitejr
Author:  Joshie225 [ Mon Oct 30, 2006 11:32 am ]
Post subject: 
Installing the cam and timing set dot-to-dot will, in theory, time the valves the way the cam grinder intended when they made the cam. With your cam the peak intake lift (intake centerline) will happen 106° after TDC. The lobe displacement angle of your cam is 110° so the cam is ground 4° advanced. If the cam, timing set and everything way made accurately the intake centerline should come up at 106° with no changes, offset bushings or other cam timing alterations. If the installed intake centerline is 111° it's 5° retarded from what the cam grinder intended.
Author:  LUCKY13 [ Mon Oct 30, 2006 3:23 pm ]
Post subject: 
As far as the cams being off on the center line even the crank and how it was ground can play a part in this. That is way you pay extra to have a crank indexed when doing stroke or regrinds on the crank. You cant blame the cam being off on the cam grinder all the time, there is to
many veribales that come into play. That is way they have degree wheels to begine with. Even the distance that the crank sets down in the block can effect this, if the block has been align honed or bored you can bet it will throw things out, even if it hasnt been align hones or such it may not have been placed right to begine with.

There is only one way to make it right, and thats degree it. But if you dont have a degree wheel or dont want to go threw the hassle you can expeirment if you are low on bottom end power and try to advance it and bring more bottom end power into play. What degree it is really at doesnt mean much except for having a proper point to work from and setting the cam as designed by the grinder. If you need more bottom, advance it, if it helps your flying, if it hurts it go back and try retarding it alittle. Ofcourse you need to be carfull and watch for valve to piston clearance, but if it was checked and you know you have plenty it shouldnt be a problem. I find that with off the shelf cams I dont ussaully run them on there designed centerline anyway. I set them to work with the combo I am working with. Which is basically if I need morwe bottom end I advance it, if I need more top end I retard it. Or I may be setting the center to gain the piston to valve clearance needed if the cam is ground this way.

Jess
Author:  69a100 [ Tue Oct 31, 2006 8:26 am ]
Post subject:  Cam Degreeing
I didn't read evey post to this topic, but here's my 2 cents. Have a free degree wheel. http://www.tavia.com/free_degree_wheel.html
Author:  CStryker [ Tue Oct 31, 2006 3:30 pm ]
Post subject: 
That's brilliant
Author:  emsvitil [ Tue Oct 31, 2006 3:53 pm ]
Post subject:  Re: Cam Degreeing
Quote:
I didn't read evey post to this topic, but here's my 2 cents. Have a free degree wheel. http://www.tavia.com/free_degree_wheel.html

Prints really good on photopaper..............
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