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Degreeing my cam: are my numbers right? Need help!
https://slantsix.org/forum/viewtopic.php?t=50993		 Page 2 of 3
Author:  sandy in BC [ Mon Feb 04, 2013 9:22 am ]
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Everything you need to know is contained in this thread.

Learn the established terms and methods for degreeing a cam. Your terms and methods dont allow us to tell you anything sensible about your cam.

Look up a stock slant grind for your car. Slantsik posted a link (salute)

Keep measuring your events until you understand how your cam differs (or not) from stock.

Determine that your cam is installed at the correct Intake Centerline.
Author:  slantsik [ Mon Feb 04, 2013 12:05 pm ]
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Read this,
http://classicinlines.com/cam_degree.asp
I gotta get to work!
bye.
Author:  nagosnell [ Mon Feb 04, 2013 12:49 pm ]
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Okay, thank you for the new posts. After work, I will go back over everything in this post, go over all of the links and measure the lobes again. Maybe I can get closer to understanding this.

I know I'm suppose to be learning, but if someone could please review slantsik's link on cam grinds and see if one of the first three specs applies to my '65 Belvedere, I would greatly appreciate it. I'm not sure if all '60’s slants had the same camshaft profile or if there were different cams for trucks and international markets. Like I said, I will take the camshaft back out if I have to but I want to avoid it if necessary.

Thanks for the help and understanding.
Author:  nagosnell [ Mon Feb 04, 2013 5:41 pm ]
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Right. For those of you still desperately bored enough to be following this, here are my new numbers...again. I will say that I found myself improperly reading the degree wheel a few times and I noticed a lot of sloppiness in the way I had my dial indicator set up. I mended these issues, measured, took down my set up, reset it, measured and measured again. I have more confidence in my new measurements. As far as how they matched up with my original measurements, I don't care... I threw them in the trash.

INTAKE
The lobe starts at 148 ATDC.
At .050 after start, it is at 174 BTDC.
At its highest lift, it is.265" at 125 BTDC.
At .050 before end, it is 77 BTDC.
The lobe ends at 31 BTDC.

EXHAUST
The lobe starts at 26 ATDC.
At .050 after start, it is at 76 ATDC.
At its highest lift, it is .265" at 126 ATDC.
At .050 before end, it is 177 ATDC.
The lobe ends at 130 BTDC.

I don't yet know what these numbers mean as I'm going home now. However, I'll attempt to do the math tonight and will hopefully have the correct numbers tomorrow. Please stick around to double check my numbers.
Author:  nagosnell [ Tue Feb 05, 2013 8:09 am ]
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Author:  Joshie225 [ Tue Feb 05, 2013 8:55 am ]
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The intake centerline should be around 106° ATDC give or take a few degrees. Are you sure you're checking the intake lobe (#2 lifter from the front) and rotating the engine clockwise as viewed from the front?
Author:  nagosnell [ Tue Feb 05, 2013 10:16 am ]
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This is completely insane! I don't know what I'm doing wrong. I'm turning the engine clockwise and I'm using the first lobe from the front as an exhaust and the next one as the intake.
Maybe I'm did something incorrect before I started measuring. After I installed my cam, I lined up the timing marks on the camshaft gear with the timing marks on the crankshaft gear. The piston is at TDC when these marks are lined up.
Is it possible that the crankshaft is one revolution off???
Is that a sane question or am I now licking windows?
Author:  nagosnell [ Tue Feb 05, 2013 10:26 am ]
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I am licking windows. The cam spins at twice per one revolution of the crank. So, can the cam be one revolution off from the crank???
Author:  Joshie225 [ Tue Feb 05, 2013 12:24 pm ]
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With the engine at #1 TDC and the timing marks lined up on the sprockets you're usually at #6 firing. So, yes, turn the crank 360° and you'll be on #1 firing.
Author:  sandy in BC [ Tue Feb 05, 2013 12:45 pm ]
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I suspect things will become clearer.....thanks Josh.
Author:  nagosnell [ Tue Feb 05, 2013 7:12 pm ]
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Embarrassingly, I turned the camshaft one Lobe starts at 34 btdc.
At .050 after start, 2 atdc.
Highest point of lobe, .258 @ 55atdc.
At .050 before end, 104 atdc.
Lobe ends at 151atdc. and measured again.

INTAKE
Lobe starts at 34 btdc.
At .050" after start, 2 atdc.
Highest point of lobe, .258" @ 55 atdc.
At .050" before end, 104 atdc.
Lobe ends at 151atdc.

EXHAUST
Lobe starts at 150 btdc.
At .050" after start, 107 btdc.
Highest point of lobe, .262" @ 58 btdc.
At .050 before end, 7 btdc.
Lobe ends at 49 atdc.

I'm a little discouraged by the maximum lift off the lobes as I was getting higher numbers before. Once again, I'll fiddle with the numbers and see if they're where they need to be. Those of you experienced, please feel free to view the numbers and give your input. Once again, thanks to those who have been helpful and patient.
Author:  sandy in BC [ Tue Feb 05, 2013 8:05 pm ]
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You did it!.

Now all you have to do is ensure the intake centerline is correct.
Author:  slantsik [ Tue Feb 05, 2013 11:57 pm ]
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[img]<img%20src="http://farm9.staticflickr.com/8355/8449149339_84a4fba1ca_m.jpg"%20width="240"%20height="188"%20alt="Camshaft_lobes"></a>[/img]

Ok ,got that to work.

Sandy said
Quote:
Now all you have to do is ensure the intake centerline is correct.
This is what you would do "normally"
Normally you would have a cam card which would tell you at how many degrees ATDC you need to put the inlet lobe centre line(the #1 line above)
Moving the inlet lobe centerline either side of the cam card spec,is advancing or retarding the cam.(cams can be ground with the advance or retard already in!!)

Now as you dont have a card we need to degree the cam another way.
You need to find the angles of the intake and exhaust lobes center lines (#1 & #1 above).
to do this you find piston TDC.
This is TDC as the intake valve is starting to open,exhaust closing.Not compression TDC(valves both closed)

Then you measure from TDC with the degree wheel.

The most accurate way is with the 0.050" method.

The second way is where you measure maximum lobe lift.

Looks like you did both which is good.
Your results make sense now.(duration seems too short,see next post)

You add the angles to give the Lobe Seperation Angle(LSA) (#10 )

You will notice in the pic TDC is exactly where the lobes intersect.
This would be a cam with 0* retard or advance.
This is also where the intake and exhaust valves are slightly open. (intake opening ,exhaust closing).

See the line going from TDC to BDC.
This is the line most important to you.(cause no cam card)
To find this line you need to half LSA (#10 )(LSA/2)

Once you halve LSA you have that line (TDC to BDC).

But where is that line in relation to TDC on your engine?
Well if you look at your degree wheel ,find your intake lobe center line number and count towards TDC the LSA/2 number.
If you end up exactly on TDC then your cam is at 0* adv/ret.
If you end up say 4* to the "Left of TDC then your cam is 4* retarded.
Right of TDC is advanced.

One other way to look at it is , if you imagine the picture above overlaid on your degree wheel ,the #1 lines and TDC-BDC lines are what you need to degree your cam.
You have measured the lines #1 .

Lets work your numbers.
we will use the highest point of lobe method here .

Intake lobe centerline = 55*ATDC
Exhaust lobe Centerline = 58* BTDC
Lobe Seperation Angle 55*+58* = LSA 113*
LSA/2 =113*/2 =56.5*
so now we have our three lines
Intake lobe centerline ,Exhaust lobe centreline, and the line to use as our "pointer" (not sure what its actually called ,camshaft cenerline maybe?)
Now we can see on our degree wheel if we count the LSA/2 degrees from our Inlet lobe centreline (55*ATDC) we end up 1.5 *right of TDC!! or 1.5* before TDC or a 1.5* advanced camshaft!!

You can also work from the exhaust lobe centerline towards TDC.
So 58* BTDC count 56.5* toward TDC ,we end up at 1.5* BTDC.
Same result.

You may also subtract the LSA/2 degrees from the Lobe centerline angles using 0 as TDC but be careful.
If subtracting from Inlet centreline ,a negative result indicates advance,a positive number represents retard.

As you can see the more accurate your lobe cennterline measurements the more accurate you will be.
By the way there is the "other "TDC and that is when the valves are both closed ,on compression.
remember the camshaft spins at half the crankshaft speed.
1.5 degrees advance is ok.
I personally would put it at 4* but I like to tinker.

Hope this has helped .
Good luck.
Brendan.
Author:  slantsik [ Wed Feb 06, 2013 2:50 am ]
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Lets do the same with you 0.050" numbers. :shock:

Quote:
INTAKE
Lobe starts at 34 btdc.
At .050" after start, 2 atdc.
Highest point of lobe, .258" @ 55 atdc.
At .050" before end, 104 atdc.
Lobe ends at 151atdc.
Start of opening 2*ATDC - closing 104*
The difference is 102* this is also your Intake duration @ 0.050"
So we halve the duration Degrees to find the lobe centerline.= 51*
Hmmm...... 4* different from the highest point of lobe method!!(55*)
......................................................................................................
Quote:
EXHAUST
Lobe starts at 150 btdc.
At .050" after start, 107 btdc.
Highest point of lobe, .262" @ 58 btdc.
At .050 before end, 7 btdc.
Lobe ends at 49 atdc.
Start opening 107*BTDC closing 7*BTDC
Difference is 100*this is your exhaust duration @0.050"
half to get centerline = 50*
Hmmmm. Highest point of lobe method shows 58*!!
........................................................................................................
If we use these numbers like in the above post.
51* and 50* = 101* LSA !!
LSA/2 = 50.5
51* - 50.5 =0.5 =0.5 * retarded!!!
A different result to 1.5* advanced!!
So you can probably say you are around 0* or TDC maybe a little advanced.
If you are confident the cam is in good condition , and you are in a hurry ,just get the engine back together.
But......

These cam numbers dont look right to me.Though they may be for a stock cam.(compare to the chart i linked earlier.) they just dont seem like long enough duration figures. (Super economy cam maybe?)
On my degree wheel it shows where the areas of valve opening and closing take place.Like this.

<img src="http://farm9.staticflickr.com/8216/8450474506_e0149c7934_m.jpg" width="236" height="240" alt="degreewheel9dg">

(Hint :use Ctrl button & "+ "button to make everything bigger )

As you can see the events at the points you describe ,kind of match with the events on the wheel shown here. Using your valve start figures.

Your inlet starts opening in the right area. 34*BTDC
your inlet valve is closing waay before BDC??? 151*ATDC

your ex opens after BDC ??? 150*BTDC and closes ATDC 49*which looks ok


Does anyone recognize this cam!?

So if your wheel does not have similar markings try printing one out like this ^and take it with you for reference.
OR
Just trust the dots!!!!
:shock: :twisted:
Brendan.
Author:  nagosnell [ Wed Feb 06, 2013 7:07 am ]
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