Topic: 1972 CB750K2 (start from scratch) project. Cases back together

[Davez134]

So I'm trying to install my cam today, trying to grasp this degreeing thing. Cam is a Webcam 41. Has marks on it just like stocker...

Installed it with those marks as a reference, set #1 at tdc, valve lash to zero, dial indicator zeroed.


Now I turn crank until valve lift is .050" as specified by timing card, degree wheel shows about 30 degrees before tdc, timing card stated intake should open 11 degrees before tdc.


So, do I need to move slotted sprocket to get to that 11 degree mark at .050"? Or am I doing something wrong?



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[iron_worker]

Does your timing card state the cam lobe center-lines? I believe you generally use the center-lines as your reference point when cam timing.

 To find the cam lobe center line:

-Find true #1 TDC (use piston stop method or an indicator through the spark plug hole)
-Adjust degree wheel for to show 0 degrees at the true #1 TDC
-Rotate the crank and record the crankshaft degrees when the valve opens up .050"
-Continue to rotate the crank until the valve begins to close again and closes to the same .050" point
-Record the crankshaft degrees

Cam lobe center-line = (Measurement #1 + Measurement #2) / 2

Check this value against your cam card to determine if you need to advance or retard your cam. You can make this check based on either the exhaust side or the intake but if you adjust one you will adjust both since we only have one cam for both duties.

IW

[Davez134]

Yeah, it states 107.5. I will do that when I get back home, going to the gym, need a mental break. Thanks!

[Davez134]

Does your timing card state the cam lobe center-lines? I believe you generally use the center-lines as your reference point when cam timing.

 To find the cam lobe center line:

-Find true #1 TDC (use piston stop method or an indicator through the spark plug hole)
-Adjust degree wheel for to show 0 degrees at the true #1 TDC
-Rotate the crank and record the crankshaft degrees when the valve opens up .050"
-Continue to rotate the crank until the valve begins to close again and closes to the same .050" point
-Record the crankshaft degrees

Cam lobe center-line = (Measurement #1 + Measurement #2) / 2

Check this value against your cam card to determine if you need to advance or retard your cam. You can make this check based on either the exhaust side or the intake but if you adjust one you will adjust both since we only have one cam for both duties.

IW

So I did all that, and lobe center shows 111 degrees. Timing card states lobe center as 107.5.

[edwardmorris]

Dave, check this out if you haven't already, might help. I've read it a few times and things are still going over my head (I guess you have to actually do this to make sense of it).

http://forums.sohc4.net/index.php?topic=103818.msg1404323#msg1404323

[Davez134]

Here is my cam card:

Last numbers I just got were (.050" lift)
Intake open: 32 btdc
Intake close: 18 abdc
32+18+180 / 2 = 140
-32 = 108 degree lobe center.

Repeated this 3 times, same numbers. Lobe center is almost spot on for intake, but open/closing numbers are way off.

And exhaust is away off too, without me moving anything, gave me like 124degree lobe center. I must be doing this wrong. For a cam that was advertised as "drop in" things are not adding up. My brain hurts.
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[timbo750]

I am no expert on cam timing but I do understand the maths behind it.

No matter where your cam sprocket is adjusted you will always get the same lobe centre measurement, this is because as you make the adjustment you are increasing one measurement and decreasing the other by the same amount so the formula will always have the same result because it is actually measuring something physical on the cam.

I think what you need to do is look at the centre point between intake opening and intake closing. it is a little confusing though as the true way to look at it is that the figure for opening BTDC is actually a negative number then if change this then the formula should be-
-32 + 18 / 2 = -7

This means that the centre of the cam lobe is 7 degrees BTDC with the current setting.

The Cam card reads that you should have the centre set at 17.5 ATDC using the formula I mentioned.

If I have got this terribly wrong someone please let me know but I am almost certain this is correct.

[Davez134]

I am no expert on cam timing but I do understand the maths behind it.

No matter where your cam sprocket is adjusted you will always get the same lobe centre measurement, this is because as you make the adjustment you are increasing one measurement and decreasing the other by the same amount so the formula will always have the same result because it is actually measuring something physical on the cam.

I think what you need to do is look at the centre point between intake opening and intake closing. it is a little confusing though as the true way to look at it is that the figure for opening BTDC is actually a negative number then if change this then the formula should be-
-32 + 18 / 2 = -7

This means that the centre of the cam lobe is 7 degrees BTDC with the current setting.

The Cam card reads that you should have the centre set at 17.5 ATDC using the formula I mentioned.

If I have got this terribly wrong someone please let me know but I am almost certain this is correct.

I got different lobe center numbers when adjusting sprocket.  There is no way the numbers could be the same. It's frustrating cause I'm good with math, and as I'm reading instructions from webcam online, it makes sense, then everything is off. Must be user error, but I can't figure out what it is

[timbo750]

Dave
ok, I misunderstood what the lobe centre measurement was. But from what I have read it seems that it is the best measurement to get right. it seems so odd that so many people have trouble with this, is cam manufacture a hit and miss procedure? I would not of thought so.

[edwardmorris]

Again, I'm sure you've gone through all of these, but in case you missed it, here's Ron's walkthrough on a K2 with the same cam

http://forums.sohc4.net/index.php?topic=36459.msg1007168#msg1007168

FWIW, apparently this cam should be a drop in, but best to dial it right. No one seems to have got this one to dial in exactly right 

[Davez134]

Again, I'm sure you've gone through all of these, but in case you missed it, here's Ron's walkthrough on a K2 with the same cam

http://forums.sohc4.net/index.php?topic=36459.msg1007168#msg1007168

FWIW, apparently this cam should be a drop in, but best to dial it right. No one seems to have got this one to dial in exactly right 

Thanks, yeah I saw that one and bookmarked it. After reading it, I thought this would be easy. Taking rest of day off and coming back fresh tomorrow

[timbo750]

I read the web cam guide, which I should of done before making my earlier comment. The only thing I can think of (because I don't think anybody else has asked this) is are you doing this with zero valve lash? Or is there a chance that somehow you got the wrong cam in the box.

[Davez134]

Yeah, I am doing this with zero lash. It is marked "web41" scribed into it. None of the numbers I'm getting even match anywhere close to their other profiles. I got back into it tonight. Weird thing is when I check the lobe center on the intake side, I get close to timing card info, but exhaust is way off. I got 108 lobe center on intake, and 123 on exhaust. I figured I would try and get them closer, so I adjusted and got 114 lobe center intake, but exhaust jumped up to 140?? I don't get it. I'm just going to line up timing marks like a stocker.

[Trad]

I'm just going to line up timing marks like a stocker.

Dang, I read through this and my head is starting to hurt now too. haha.  Your above comment is all I'm doing with my webcam when I install it so don't feel so bad. 

[Blackfin5]

Without a slotted adjustable sproket, you can only adjust the lobe CL number by moving the cam sprocket by one tooth either way.  Even then its frustrating because each time you measure with the dial indicator is slightly different and make sure you find exact TDC with a piston stop.

I was suppossed to be 104.5 for both intake and exhaust lobes.  At 104.5 intake I was about 105.25 exhaust.  I finally averaged out both libes to about 104.75.  I say "about" because each measure is slightly different than the last.

[Davez134]

Without a slotted adjustable sproket, you can only adjust the lobe CL number by moving the cam sprocket by one tooth either way.  Even then its frustrating because each time you measure with the dial indicator is slightly different and make sure you find exact TDC with a piston stop.

I was suppossed to be 104.5 for both intake and exhaust lobes.  At 104.5 intake I was about 105.25 exhaust.  I finally averaged out both libes to about 104.75.  I say "about" because each measure is slightly different than the last.

I have an APE adjustable sprocket. I am able to make the adjustments, just can't figure why exhaust is so far off. 

[MRieck]

Without a slotted adjustable sproket, you can only adjust the lobe CL number by moving the cam sprocket by one tooth either way.  Even then its frustrating because each time you measure with the dial indicator is slightly different and make sure you find exact TDC with a piston stop.

I was suppossed to be 104.5 for both intake and exhaust lobes.  At 104.5 intake I was about 105.25 exhaust.  I finally averaged out both libes to about 104.75.  I say "about" because each measure is slightly different than the last.

I have an APE adjustable sprocket. I am able to make the adjustments, just can't figure why exhaust is so far off.

Because it is a Web cam. You will never achieve the LC #'s on the card. First off put the lash you will be running in place. You want to time a cam with the actual lash in place to get a real idea of what will be happening under running conditions. Your opening/closing  #'s will be less but who cares.....they are just #'s.
 Split that cam timing trying to get opening closing #'s the same. Example...intake opening 6 degrees BTDC and exhaust closing 6 degrees ATDC. I used lower #'s because having the lash in place will lower the #'s.

[Davez134]

Without a slotted adjustable sproket, you can only adjust the lobe CL number by moving the cam sprocket by one tooth either way.  Even then its frustrating because each time you measure with the dial indicator is slightly different and make sure you find exact TDC with a piston stop.

I was suppossed to be 104.5 for both intake and exhaust lobes.  At 104.5 intake I was about 105.25 exhaust.  I finally averaged out both libes to about 104.75.  I say "about" because each measure is slightly different than the last.

I have an APE adjustable sprocket. I am able to make the adjustments, just can't figure why exhaust is so far off.

Because it is a Web cam. You will never achieve the LC #'s on the card. First off put the lash you will be running in place. You want to time a cam with the actual lash in place to get a real idea of what will be happening under running conditions. Your opening/closing  #'s will be less but who cares.....they are just #'s.
 Split that cam timing trying to get opening closing #'s the same. Example...intake opening 6 degrees BTDC and exhaust closing 6 degrees ATDC. I used lower #'s because having the lash in place will lower the #'s.

So right now I have intake opening at 23degrees BTDC and exhaust closing at  3 degrees ATDC. So you're saying get those numbers closer ( like 13 degrees, the middle, if possible)? Right now still zero lash, will change that next go around.

[Davez134]

So I've never been one to give up...



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[edwardmorris]

Its still going over my head, but I see two 103.5s in there so I take it  you got it lined up?

PAARTAAYY!

[Davez134]

Yeah! Having a few drinks to celebrate! Cam was way advanced (and I was a little retarded) I actually made a call to webcam, talked with a girl named Faith who straightened me out! Spent over 30 minutes on phone with me. Now I can move on to other things...




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[Nuffsa Fugginnuff]

Subscribed. And, enjoying the ride.

[timbo750]

Dave,  congrats on getting the cam sorted. The lobe centres didn't end up too far from spec. I am actually using a web cam in one of my engines now know exactly what I need to do to set it up right. Thanks for documenting this so well.

[disco]

Well done on sorting out the your cam issues.

btw that's a real neat job you done with the Gordon kit! Looks factory!

[iron_worker]

What did you end up doing to sort it out?

IW