cam specs dont match when degreed

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PredaFran

PredaFran

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yesterday I went over the cam installation, found TDC with a stop, and degreed the cam to make sure it didnt need any advancing or retarding.
When I checked the intake centerline I kept getting consistent results at around 102.75 give or take 1/4 degree because of the small degree wheel. it was supposed to be 106 on the intake so it was around 3 degrees advanced. before any changes, I wanted to make sure that the measurement was right so I made sure there was no thick lube on the roller lifters and that my dial indicator was clamped down properly. after removing the sprung part on it and bolting it down to get rid of any play. I still got the same results so I decided to check it with the exhaust centerline, to make sure that it advanced 3 degrees, but it measured at 117. the centerline is supposed to be 114, so that exhaust centerline is retarded. Since the intake is advanced compared to the cam card and the exhaust is retarded does it mean the cam was ground incorrectly.
The lsa is still 110 but how is this gonna affect the way the engine runs? 360 magnum 30 over with Edelbrock heads and 30 over sealed power pistons. any advice or criticism on this will be appreciated. thanks in advance FABO!

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how did you degree he cam .050 lift timing or down equal mount from the pointy nose
find out which way grinder wants you to do it
asymetrical cams will check different with each method
are you checki on efde of the lifter or cup ?
 
Wyrmrider said:
how did you degree he cam .050 lift timing or down equal mount from the pointy nose
find out which way grinder wants you to do it
asymetrical cams will check different with each method
are you checki on efde of the lifter or cup ?
Click to expand...
i did the .50 lift down both sides of the lobe. checking on the cup of the lifter. ill email the grinder
 
PredaFran said:
yesterday I went over the cam installation, found TDC with a stop, and degreed the cam to make sure it didnt need any advancing or retarding.
When I checked the intake centerline I kept getting consistent results at around 102.75 give or take 1/4 degree because of the small degree wheel. it was supposed to be 106 on the intake so it was around 3 degrees advanced. before any changes, I wanted to make sure that the measurement was right so I made sure there was no thick lube on the roller lifters and that my dial indicator was clamped down properly. after removing the sprung part on it and bolting it down to get rid of any play. I still got the same results so I decided to check it with the exhaust centerline, to make sure that it advanced 3 degrees, but it measured at 117. the centerline is supposed to be 114, so that exhaust centerline is retarded. Since the intake is advanced compared to the cam card and the exhaust is retarded does it mean the cam was ground incorrectly.
The lsa is still 110 but how is this gonna affect the way the engine runs? 360 magnum 30 over with Edelbrock heads and 30 over sealed power pistons. any advice or criticism on this will be appreciated. thanks in advance FABO!

View attachment 1715489773 View attachment 1715489779
Click to expand...



If it's 3 degrees advanced on the intake them the exhaust has to be 117. So that is correct.

You either need to retard the cam 3 degrees or live with it. No way would I put it in at 103. I'd rather see it at 108 than 103.
 
yellow rose said:
If it's 3 degrees advanced on the intake them the exhaust has to be 117. So that is correct.

You either need to retard the cam 3 degrees or live with it. No way would I put it in at 103. I'd rather see it at 108 than 103.
Click to expand...
Hydraulic roller. Should he have a mechanical roller in there to check it with?
 
that
and he's checking the nose of an asymetrical lobe
which is not lined up with the .050 seat timings for io ic exo exc
 
Wyrmrider said:
that
and he's checking the nose of an asymetrical lobe
which is not lined up with the .050 seat timings for io ic exo exc
Click to expand...

No arguments here, and I`m not an expert by any means, but I have never checked a cam that was what it was supposed to be all the way thru .
 
An easy thing to remember is, the total for the intake/exhaust c/l will always add up to the same number....... no matter where you put it.

Cam card says 106 & 114=220

You got basically 103 & 117, also equals 220.

LSA is int c/l + ex c/l divided by 2.
The LSA is part of how the cam is made and is a fixed figure.

If you don’t have a 9 way timing set, you’ll likely need to get some offset cam keys to get the cam closer to where you want it.

As was already mentioned, on a non-symmetrical lobe...... the open/close timing points won’t agree with the “centerline” method for determining installed position.
The open/close method is technically more correct, but since the lifter is moving less per degree of rotation at that point of the lobe, it’s easier to be off with the measurements.
It’s a mathematical mid-point, not necessarily the middle of the peak of the lobe.
On a symmetrical lobe, the open/close points and c/l would agree with each other.
 
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toolmanmike said:
Hydraulic roller. Should he have a mechanical roller in there to check it with?
Click to expand...

Or just put the indicator on the edge of the lifter body instead of the plunger.

Although, it’s unlikely the spring inside the indicator is enough to compress the lifter at all.
 
Rerun at .100" and .300" or .310" lifter lift. If they all agree, then the cam very probably symmetrical and is simply advanced. The numbers near peak lift in particular ought to show different ICL and ECL if the lobe is assymetrical.
 
PRH said:
Or just put the indicator on the edge of the lifter body instead of the plunger.

Although, it’s unlikely the spring inside the indicator is enough to compress the lifter at all.
Click to expand...
I just did a different engine yesterday with the indicator plunger directly on the lifter plunger... the lifter spring was far, far, far stronger than the indicator spring. Easy to that tell with your finger. No contest!
 
PRH said:
An easy thing to remember is, the total for the intake/exhaust c/l will always add up to the same number....... no matter where you put it.

Cam card says 106/114=220

You got basically 103/117, also equals 220.

Lsa is int c/l + ex c/l divided by 2.

If you don’t have a 9 way timing set, you’ll likely need to get some offset cam keys to get the cam closer to where you want it.

As was already mentioned, on a non-symmetrical lobe...... the open/close timing points won’t agree with the “centerline” method for determining installed position.
The open/close method is technically more correct, but since the lifter is moving less per degree of rotation at that point of the lobe, it’s easier to be off with the measurements.
It’s a mathematical mid-point, not necessarily the middle of the peak of the lobe.
On a symmetrical lobe, the open/close points and c/l would agree with each other.
Click to expand...

That is a good point ! I never considered that ....
My Oregon cam came out 1.5* off when I checked all the events . Maybe that is why ?
 
OBTW, OP, the chain is likely gonna stretch a degree or 2 with not too much operating time.... so you may end up pretty close to where you want after some engine operation anyway.
 
I’m not suggesting the cam is reading 3* advanced because of the checking method.

I usually do both, and my experience is that the difference between the two methods is usually closer to 1*.

I would move the cam.
 
Thank you everyone for the responses and information, I really appreciate you guy's taking you time to give me some feedback on this. I contacted Oregon and they said they check em at .100 so I'll run that next and see what it says. I have a clothes double roller that is adjustable so I'll retard it to 108 if needed. My only question and it's because I'm curious if I advance a cam from 106 to 103, wouldn't the exhaust go from 114 to 111?
@yellow rose could you explain why if you got any time. I'm interested in learning something new if possible.
Again thank you all for your feedback and responses to the thread , it's my first engine build and since my machineshop teacher passed away recently I have no one else to help me with this.
 
My only question and it's because I'm curious if I advance a cam from 106 to 103, wouldn't the exhaust go from 114 to 111?
Click to expand...

First off, 103 + 111 don’t equal 220, as 106 + 114 does.
That’s your first clue that you’re missing something obvious.

Rather than tell you, I’m going to let you think about it for a while.

Think about what those numbers are actually referring to/representing.
The 106 and the 114....... what do those numbers mean?

You could also invision the “v” made by the two centerlines on the degree wheel...... and what happens to either one....... when you move the other one.
Think of the V as a wedge thats the exact size/distance of the degrees between the intake & exhaust lobes, and that can be moved fore or aft on the degree wheel........ but the size of it can’t be changed.

Edit:
Well, after visualizing it....... it’s actually not going to be a wedge.
It’s all the area between the two lines that aren’t in the pie shaped wedge.

There is still a V shape made from two c/l’s on the wheel...... but that represents the area that’s not actually between the c/l’s.
It represents what’s left.

For the OP’s cam....... on the wheel....... there is going to be 220* between the 2 c/l’s(LSA x 2).
The wedge that’s left is the remaining 140*.
 
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PredaFran said:
Thank you everyone for the responses and information, I really appreciate you guy's taking you time to give me some feedback on this. I contacted Oregon and they said they check em at .100 so I'll run that next and see what it says. I have a clothes double roller that is adjustable so I'll retard it to 108 if needed. My only question and it's because I'm curious if I advance a cam from 106 to 103, wouldn't the exhaust go from 114 to 111?
@yellow rose could you explain why if you got any time. I'm interested in learning something new if possible.
Again thank you all for your feedback and responses to the thread , it's my first engine build and since my machineshop teacher passed away recently I have no one else to help me with this.
Click to expand...


Think about what you are asking. PRH already gave a good explanation of it, but consider the matter.

The intake and exhaust lobes NEVER change position relative to each other. Sooooo...if your cam is ground on a 110 Lobe Seperation Angle, that means that no matter what you do, the angle between the intake and exhaust lobe on any given cylinder must add up to 110.

Soooo...if you install your cam on a 106 Intake Center Line, the exhaust center line MUST BE 114 (106 plus 114 equals 220 divided in half equals 110).

If you move the Intake Center Line to say...100 then because the lobe position on the cam is fixed, the exhaust center line MUST be 120 because the sum of the intake and exhaust center lines MUST equal 110, which is the Lobe Seperation Angle.

So let's say you decide you want to install the cam with a 114 Intake Center line. Why you would do that, I can't say, but we are doing math so...why not.

If the Intake Center line is now 114, because the lobe position is fixed, the exhaust center line MUST BE 106, because the sum of the two must equal 110.

So think about this until you get your head around it.

Go to mgispeedware.com and put all your cam numbers into the program and then change your intake center line and see what happens.

You can see graphically what you do when you move the intake center line around.
 
People often get hung up on the “advance” or “retard” thing, and how it relates to the numbers.

If you remember what the c/l numbers are referring to, it should keep you straight.
It can sometimes be easier to think of it in terms of direction.
You are moving the cam clockwise or counter-clockwise relative to the crank.
Whichever direction you move one lobe...... the other goes with it.

Look at the(typical) degree wheel....... if you moved the cam from an int c/l of 106...... clockwise 3*, the new c/l is 103.

If the ex c/l was 114 when the intake c/l 106, and you moved the cam 3* clockwise.......if you look on the exhaust side of the tdc mark of the wheel........what is 3* clockwise on the degree wheel from 114?(it’s 117).
 
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did the grinder make the master or is it a copy?
If the grinder made a copy master does he have any idea about the design of the original?
or how he original was degreed?
If you had a after ground print you could see if the point was exactly in the center of the lobe- between the timing points
what was the original?
 
yellow rose said:
Think about what you are asking. PRH already gave a good explanation of it, but consider the matter.

The intake and exhaust lobes NEVER change position relative to each other. Sooooo...if your cam is ground on a 110 Lobe Seperation Angle, that means that no matter what you do, the angle between the intake and exhaust lobe on any given cylinder must add up to 110.

Soooo...if you install your cam on a 106 Intake Center Line, the exhaust center line MUST BE 114 (106 plus 114 equals 220 divided in half equals 110).

If you move the Intake Center Line to say...100 then because the lobe position on the cam is fixed, the exhaust center line MUST be 120 because the sum of the intake and exhaust center lines MUST equal 110, which is the Lobe Seperation Angle.

So let's say you decide you want to install the cam with a 114 Intake Center line. Why you would do that, I can't say, but we are doing math so...why not.

If the Intake Center line is now 114, because the lobe position is fixed, the exhaust center line MUST BE 106, because the sum of the two must equal 110.

So think about this until you get your head around it.

Go to mgispeedware.com and put all your cam numbers into the program and then change your intake center line and see what happens.

You can see graphically what you do when you move the intake center line around.
Click to expand...

PRH said:
People often get hung up on the “advance” or “retard” thing, and how it relates to the numbers.

If you remember what the c/l numbers are referring to, it should keep you straight.
It can sometimes be easier to think of it in terms of direction.
You are moving the cam clockwise or counter-clockwise relative to the crank.
Whichever direction you move one lobe...... the other goes with it.

Look at the(typical) degree wheel....... if you moved the cam from an int c/l of 106...... clockwise 3*, the new c/l is 103.

If the ex c/l was 114 when the intake c/l 106, and you moved the cam 3* clockwise.......if you look on the exhaust side of the tdc mark of the wheel........what is 3* clockwise on the degree wheel from 114?(it’s 117).
Click to expand...

Yellow rose and PRH, I went over what you said and checked the website YR mentioned. I went through some of my notes and took a look at the degreeing wheel and it all makes sense now. Thank you for the help to make things click. I went over everything and I managed to get everything degreed exactly at 106 CL on the intake. So thank you for your help understanding how everything worked together helped me do everything the proper way and now I feel confident in the work I did.
Wyrmrider said:
did the grinder make the master or is it a copy?
If the grinder made a copy master does he have any idea about the design of the original?
or how he original was degreed?
If you had a after ground print you could see if the point was exactly in the center of the lobe- between the timing points
what was the original?
Click to expand...

It's the master from the grinder and they checked everything for me so I was pretty sure it was an Error on my end, just wanted to get some insight from people that have been building engines for longer than I have been alive.
 
PredaFran said:
Yellow rose and PRH, I went over what you said and checked the website YR mentioned. I went through some of my notes and took a look at the degreeing wheel and it all makes sense now. Thank you for the help to make things click. I went over everything and I managed to get everything degreed exactly at 106 CL on the intake. So thank you for your help understanding how everything worked together helped me do everything the proper way and now I feel confident in the work I did.


It's the master from the grinder and they checked everything for me so I was pretty sure it was an Error on my end, just wanted to get some insight from people that have been building engines for longer than I have been alive.
Click to expand...



LOL...unless you are 12 years old none of us are THAT old!!!

Glad it's making sense to you.
 
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