Cam timing adjustment?

XsJosh

XsJosh

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20210327_180306.jpg

So I've been fighting with tuning since I rephased my motor (8 years ago?) At the time I checked the cam timing and found it 2.5 - 3 degrees retarded (if memory serves) thought how bad could it be and put it together. Re-measured last weekend still getting the same 2.5 - 3 degrees retarded. Now to the actual question, I'm thinking I want to advance my cam 3-4 degrees and I just want to run my numbers and logic. To move 4 degrees on the degree wheel on the crank I need to move 2 degrees on the cam? The cam needs to move clockwise in relation to the sprocket? And finally I came up with 2 degrees at the diameter of the flange that the cam presses against should be about 1mm? Sorry to be so long winded and thanks in advance.
 
Not exactly clear to me
Please give more info
Clockwise from what viewpoint ?
Meaning of that
And finally I came up with 2 degrees at the diameter of the flange that the cam presses against should be about 1mm?

I believe the cam rotates with half the rpm of the crank on a 4 stroke
Are we talking of moving the cam one or more cogs with the cam chain and crank fixed
Or are we talking of loose chain wheels

For a stock machine there are markings for the cam and crank position that when chain is riveted
are locking them relative to each other
 
Ok, so looking at the cam from the alternator side as in my picture, yes the cam rotates at half crank rpm that's why I'm thinking to gain 4 degrees timing at the crank I need to advance the cam 2 degrees.
20210330_202422.jpg
My cam is in the freezer for the night and I'm going to heat the sprocket tomorrow evening and drop it back on.
 
To "advance" the cam.... imagine keeping the sprocket stationary. The cam needs to move forward in the direction of rotation. In other words, when the tooth hits vertical, the cam has already "advanced" past that point and is further forward of where the tooth is. Looking from the alternator side, the sprocket stays stationary and the cam rotates "counterclockwise."
XsJosh said:
....why I'm thinking to gain 4 degrees timing at the crank I need to advance the cam 2 degrees.
Click to expand...
Correct.
 
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Keep in mind too.... there's 36 teeth on the cam.... divided by 360° means each tooth on the cam equals 10° of cam rotation. That translates to 20° at the crank. So 5° "engine advance" would be 1/4 of a cam tooth. That all make sense?
 
Its late here so I cant figure it out
If the advance shall be 1/ 5 --1/ 6 of a cam tooth
1 mm ?
How is that done ..?? is there that much play after the Heating and Cooling operation
and can one sight that in ..so it don't get 2 mm
Any fixtures ??
 
Jan_P said:
Its late here so I cant figure it out
If the advance shall be 1/ 5 --1/ 6 of a cam tooth
1 mm ?
How is that done ..?? is there that much play after the Heating and Cooling operation
and can one sight that in ..so it don't get 2 mm
Any fixtures ??
Click to expand...
20210330_215124.jpg

Ok so the 1mm is what I figured using some rough measurements and geometry as being roughly equal to 1 degree at the major diameter of the boss that the cam is pressed up against. For reference the slot in the above picture measures about 3mm.
 
Remember, the cam moves at 1/2 crank speed, so from a 191.5 mm. circumference measurement, 1* of crank rotation=.265 mm. What I've used for years to adjust the 447 cam timing is .008" (.203 mm.) per degree as measured at the corner of the notch (arrived at by measuring the diameter of the camshaft boss to find the circumference; thank you, Pythagoras). To mark the sprocket I lay a feeler gauge along the appropriate side of the notch and snap the spot with an automatic punch. Setting valve timing a little to the retarded side tends to wake things up a bit in the higher rpm range.
 
Still not sure I understand this maybe to difficult could not sleep because a broken rib
The cam has a sprocket with teeth moving the chain one cog gives to much

. there's 36 teeth on the cam.... divided by 360° means each tooth on the cam equals 10° of cam rotation.

At the time I checked the cam timing and found it 2.5 - 3 degrees retarded
Is that measured at cam or crank ??

So the goal was --
want to advance my cam 3-4 degrees

The cam is now separated from the sprocket and had the line center in the slot. Before
If the adjustment is concerning the 3-4 degrees on the cam .I dont think the Crank gets involved.
If the Circumference is 191.5 there at the junction between sprocket and cam ..
1 degree will be 191.5/ 360 mm/ degree .. 0.532 mm ( Strictly speaking av curved length )
If one want 3 degrees 3 x 0.532 mm = 1.6 mm

So from the state before ..line center notch ??? one moves it 1.6 mm to the correct direction and gets the 3 degrees adjustment
Between the sprocket and Cam lobes.

Thinking ?? what direction if the camlobes shall advance .other equal --
Machine rotating when running seen from the left side is it clockwise ??
If advance means hitting the valves sooner the cam rotatates clockwise relative the Sprocket so the line on the marking
moves to the left 1.6 mm ( ? Notch on cam and Line on Sprocket ? )
Might be wrong here a sketch perhaps
 
Jan_P I had to press the cam sprocket off and on when I rephased, and to complicate things even further I'm running a 256 cam in a 447 motor. The engine runs CCW viewed from the alternator side, therefore the cam must be rotated CCW in relation to the sprocket, my target right now is 1mm assuming 1 degree on the cam = .53mm therefore 1mm should be just under 2 degrees of cam and between 3-4 degrees at the crank. Set up the way it has been, I have very little low end torque, very low vacuum numbers and a lot of trouble tuning (especially idle) but it does really wake up in the higher revs.
20210331_052655.jpg
 
Grizld1, I agree with everything you've said so far, I even had come up with the same .oo8" the first time I did the math (I'm not sure how). Up to this point I've been doing very dirty measurements (using a plastic scale) tonight I plan on measuring with my good calipers from work and going over the math 1 last time while my sprocket warms on the stove top...
 
I'd use a scriber for marking it. Maybe a paint dot first, then scribe in the paint.
(Or maybe the paint will burn off when heating the sprocket?)

A super expensive solution is the adjustable cam sprocket Web Camshafts sell. 295 dollars. The shrink/press fit sprocket hub can be fitted randomly. The sprocket is slotted to allow at least 10 degrees adjustment at cam, since it is 36 teeth.
 
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XsJosh said:
Jan_P I had to press the cam sprocket off and on when I rephased, and to complicate things even further I'm running a 256 cam in a 447 motor. The engine runs CCW viewed from the alternator side, therefore the cam must be rotated CCW in relation to the sprocket, my target right now is 1mm assuming 1 degree on the cam = .53mm therefore 1mm should be just under 2 degrees of cam and between 3-4 degrees at the crank. Set up the way it has been, I have very little low end torque, very low vacuum numbers and a lot of trouble tuning (especially idle) but it does really wake up in the higher revs.View attachment 188113
Click to expand...

Thank you Sir for the Patient answer and well informed input as always from mr Grizid and others
I shall read and watch ..later tonight .. Here is a lot going on that I don't know about at this point in time
But it seems a little clearer if the yellow markings are where the line is after and arrow rotation.
As well as the 3-4 on the crank
Perhaps difficult performing the actual work do it right First thought getting it seated perpendicular to the cam center line so it wont wobble
and at the right angle with warm part.
 
IMG_20210331_184304.jpg

Before during and after, I was really surprised how easily it slipped together and how much time I had to get it just right. We won't talk about the first try...
 
Last edited:
20210331_184558.jpg finally some real world measurements... metric btw
So 54 x 3.14 = 169.56
169.56 ÷ 360 = .471 so 1 degree is .471mm
.471 x 2 = .942 so to advance my cam timing
2 degrees I needed to move just under 1mm CCW.
To help myself visualize this I measured the notch in the cam 3.2mm blew up a picture on my phone until it was approximately 32mm then set my calipers to .95mm and help it to the screen. I feel that I got fairly close. I may check with the degree wheel after dinner.
 
Difficult
Is the cam in 2 halves spit at the middle ?
Stock ??
I have not seen that if i remember right on 2 or 3 cams for 1980
in # 3 there is a picture separated and one can see half moon shaped holes
Are those for locating ..and it is not in right place at the picture
And the Allen bolts holds it together ??

What prevents the now adjusted sprocket to rotate on the axle
Shrink fit ?
And are the Allen bolts locked in some way ?
 

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