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degreeing cam [FIXED]
https://slantsix.org/forum/viewtopic.php?t=45885		 Page 1 of 2
Author:  kielbasa [ Sun Aug 07, 2011 11:09 pm ]
Post subject:  degreeing cam [FIXED]
okay, i am in the middle of degreeing my cam, and i have ran into a bump i n the road.
oregon cam grid #125

first i set the motor to TDC with my depth height gauge
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then i turned the motor over until highest point on cam lobe, and set gauge to 0
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this is where the degree wheel sits at max lift, about 78
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turned motor over counter clockwise till guage read .050, degree wheel reads 32
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roll motor back over clockwise, past max lift, and back down to .050. degree wheel reads 57
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cam card reads, that the intake should open at 0 BTDC, and close at 32 ABDC. now i got 1 number right, but what the hell happened with the other? help would greatly be appreciated.

here is the "cam card"
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Author:  CNC-Dude [ Sun Aug 07, 2011 11:43 pm ]
Post subject: 
Your the second person i've seen this week try to degree a cam using the method of starting in the middle of the process instead of the begining ...and end up lost. Try starting with zeroing your indicator with the lobe on the heel of the cam which is the begining. Also, never rotate the crankshaft counterclock wise once you have zeroed your indicator, you can introduce error into your readings from slack in the chain. Always keep it rotating in the direction it rotates when the engine is running(clockwise). When you have found true TDC, starting with the indicator @zero on the lobe, rotate it slowly, and as the indicator nears .050 lift you should see the TDC mark(0) coming up on your degree wheel if its installed straight up. If you get any other reading, this will tell you if its advanced or retarded in its installation. Once you get to checking the LSA, this should also correspond to match your @.050 valve opening data to verify if its straight up or advanced/retarded. Hope this helps.
Author:  kielbasa [ Mon Aug 08, 2011 12:19 am ]
Post subject: 
well i have read several different write ups, and videos, and they all did it this way. my opening number is just so off, i don't understand why
Author:  CNC-Dude [ Mon Aug 08, 2011 9:13 am ]
Post subject: 
Its just a poor method to try and do this as you are seeing. All cam companies use the cam lobe on the heel method as the zero point to begin with and all reference points on your cam card are also referenced from that beginning point, so start there and you will be fine. The method you are using will only let you measure the intake centerline and nothing else will correspond because you are zeroing with the lobe at full lift, instead of starting at zero lift like you should. Start from the beginning as I mentioned and you will see the difference.
Author:  Joshie225 [ Mon Aug 08, 2011 1:52 pm ]
Post subject: 
I don't see where you went some distance down (say .050") from TDC both before and after TDC and then found the mid point to zero your degree wheel.

If you are going using the intake centerline method you should find the peak lift about 106° after TDC if the cam and timing set are all made exactly as designed.

You are not reading the degree wheel correctly. And your 78° reading is actually 102° ATDC. Why the marks count down after 90° I don't get. It's dumb. Your 32° is actually 148° ATDC. So 148 + 57 = 205, 205/2 = 102.5° ATDC intake centerline. Your cam is 3.5° advanced from how it was ground ASSUMING you found TDC correctly.
Author:  kielbasa [ Mon Aug 08, 2011 2:37 pm ]
Post subject: 
okay, i did it the correct way, now i see how lame that first method was. but from what i can tell, there is 1 degree between opening and closing. It seems like its 3 degrees off from opening, and 2 degrees from closing. would i just find a 2 degree bushing and call it good? I really appreciate all the help, especially CNC-Dude, thanks for giving me the correct way.

TDC
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Rolled motor over until i hit the heel of the lobe, and set gauge to 0
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Rolled motor over clockwise to .050, got a degree of 3
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Rolled motor over till tip of cam to see my lift of .277
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Rolled motor over back down to .050 on the opposite side of the lobe. to get a degree of 30
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Here is my cam card again
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Author:  CNC-Dude [ Mon Aug 08, 2011 4:48 pm ]
Post subject: 
Glad it was a little smoother of a method for you to use. Glad to have been able to help you out.
Author:  kielbasa [ Mon Aug 08, 2011 4:58 pm ]
Post subject: 
hey dont go anywhere i still need a little help on why, i am 2 degrees from closing, and 3 from opening.. and should i use a shim. i am not sure, correct me if im wrong, but this would mean my cam is about 3 degrees advanced? do i want it advanced that much, or at all? or should i shim it, and what degree offset bushing do i use. WE ARE ALMOST THERE!
Author:  Dart270 [ Mon Aug 08, 2011 5:37 pm ]
Post subject: 
2 deg advanced will be just about perfect, in my book. If I understand correctly, you are at 104 deg intake centerline. I would leave it alone and not set to 106 intake centerline.

Lou
Author:  olafla [ Mon Aug 08, 2011 5:40 pm ]
Post subject: 
Great pics, kielbasa.
There is a need for an illustrated, step by step, detailed description of how to degree a cam in the FAQ. May I suggest to you - and to the moderators, that you go over the steps from start to finish, after you get feedback on all your questions? I hope you can get some pics of the steps needed to modify the cam advance as well. You could then make a summary here in this thread, for members to comment on - just to avoid missing out on details, and use the info to make a new locked thread on 'How to degree a cam' for the FAQ, with all steps and pics included?

Olaf.
Author:  kielbasa [ Mon Aug 08, 2011 6:06 pm ]
Post subject: 
i tried the centerline way a few more times, i came up with 147.5 and 57.5 which comes out to 102.5 centerline, which would be 3.5 degrees advanced

and the other way, i get 3 degrees on open, and 2 on close... wow something is a little off, but either way im just about 3 degrees advanced which would be a good thing? keep in mind that this is a full daily driver, basically stock engine.
Author:  kielbasa [ Mon Aug 08, 2011 6:12 pm ]
Post subject: 
and thank you very much olafla, but im still having some issues and confusing, i don't think im the one to do all that, but i guess im doing it basically right, maybe this cam is just goofy. (THANKS JOSH! :wink:) Juuust kidding. but the mods are more then welcome to use my pictures if they want. or if they want or need more, let me know, but before i start buttoning everything up. just let me know
Quote:
Great pics, kielbasa.
There is a need for an illustrated, step by step, detailed description of how to degree a cam in the FAQ. May I suggest to you - and to the moderators, that you go over the steps from start to finish, after you get feedback on all your questions? I hope you can get some pics of the steps needed to modify the cam advance as well. You could then make a summary here in this thread, for members to comment on - just to avoid missing out on details, and use the info to make a new locked thread on 'How to degree a cam' for the FAQ, with all steps and pics included?

Olaf.
Author:  CNC-Dude [ Mon Aug 08, 2011 6:30 pm ]
Post subject: 
Maybe since you have a little discrepency you should recheck a few things just to satisfy that you are on the right track. I would double check your true TDC by using a different method than you used originally....just to have a double assurance it is what it is. Maybe try the positive stop method since it eliminates any piston dwell that isn't noticeable by using the dial indicator method and see if it varies from your original TDC reference pont. If its the same, then at least you elimated any error and had another method to double check and confirm your findings. I also would leave it advanced. It will be more advantageous since it is a street driver. I also like seeing guys use nice quality tools...nice Starrett stuff 8)
Author:  Joshie225 [ Mon Aug 08, 2011 6:38 pm ]
Post subject: 
102.5° intake centerline is a little on the advanced side. It will run there quite well and be peppy off idle, but might run out of steam a couple hundred RPM sooner than if installed at 106°. If you have a 2° bushing and can get it to 104.5° I think that would be just about perfect.

I 2nd CNC-Dude's recommendation of double checking TDC. You must measure some distance down from TDC (.100" works) on the rising and falling side and the degree measurement on the wheel must be the same. If it's not then your TDC is off.
Author:  kielbasa [ Mon Aug 08, 2011 8:36 pm ]
Post subject: 
Okay, I got a different degree wheel (larger comp cams one) I centered it perfectly on the end of the crank. made a new thinner pointer. I am Absoultely Positive that I have TDC set correctly. I did not take pictures, because my camera phone sucks taking dark pictures. I will try to use the old ladys camera later if I get the chance.

Anyways these were the numbers that i came up with.
3° @ .050 OPEN BTDC. 30.5° @ .050 CLOSE ABDC
Cam Card states 0° BTDC 32° ABDC

Also did the Centerline Method.
58° @ .050 from Peak Lift
148.5° @ .050 from Peak Lift

148.5+58=206.5, 206.5÷2=103.25°
Cam Card States 106°
106-103.25=2.75° of Advance

This leads to a question, of course by now im sure we are all confused why im getting different amounts of degrees between opening and closing(if you have the answer why, please shine your knowledge).
But with the Centerline Method, even if my TDC was a degree or 2 off, or any amount as a mater of fact, i would always get the same # of Degrees at the very end. Please correct me if am wrong, but am I gauranteed to have 2.75° of advance? And is that too little, too much, or just right for advancement?
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