Posted By: 426runner
Cam installed centerline question - 11/02/10 09:40 PM
What would be the affect on an engine if the cam was installed at 105 c/l when the card said it was meant for 108 deg c/l? 
Cam installed centerline question
Posted By: 70AARcuda
Re: Cam installed centerline question - 11/02/10 10:09 PM
it will run better...lol
you are 3 degrees advanced...advancing the cam with help the low end performance...increase cylinder pressure by closing the instake valve sooner..
Advancing the camshaft means that you are starting the opening and closing process sooner in the cycle. It generally improves low-speed torque and mid-range power while sacrificing top-end hp. Conversely, retarding the cam detracts from low- and mid-range power in order to help top-end power. Generally, moving a camshaft a couple of degrees will not make dramatic changes to the engine's power curve
you are 3 degrees advanced...advancing the cam with help the low end performance...increase cylinder pressure by closing the instake valve sooner..
Advancing the camshaft means that you are starting the opening and closing process sooner in the cycle. It generally improves low-speed torque and mid-range power while sacrificing top-end hp. Conversely, retarding the cam detracts from low- and mid-range power in order to help top-end power. Generally, moving a camshaft a couple of degrees will not make dramatic changes to the engine's power curve
Posted By: Stanton
Re: Cam installed centerline question - 11/02/10 10:16 PM
Your engine will be retarded !
The intake valve opens later and closes later. Since it closes ABDC that's a hair less compression the motor will make. Likewise the exhaust valve will open sooner, releasing combustion pressure sooner. All this equates to a loss of power.
The intake valve opens later and closes later. Since it closes ABDC that's a hair less compression the motor will make. Likewise the exhaust valve will open sooner, releasing combustion pressure sooner. All this equates to a loss of power.
Posted By: goldmember
Re: Cam installed centerline question - 11/02/10 10:31 PM
Quote:Is this a joke? Retarded?
Your engine will be retarded !
The intake valve opens later and closes later. Since it closes ABDC that's a hair less compression the motor will make. Likewise the exhaust valve will open sooner, releasing combustion pressure sooner. All this equates to a loss of power.
Posted By: Sport440
Re: Cam installed centerline question - 11/03/10 01:00 AM
Quote:
Your engine will be retarded !
The intake valve opens later and closes later. Since it closes ABDC that's a hair less compression the motor will make. Likewise the exhaust valve will open sooner, releasing combustion pressure sooner. All this equates to a loss of power.
You have it backwards. If the intake valve reaches peak lift earlier at 105* ATDC vs 108* ATDC
Then it is indeed advanced and not retarded.
For the OP, if thats where your at. Thats not a bad ICL area. IMO 101* to 106* for alot of engine combos is a good general ICL. mike
Posted By: 602heavy
Re: Cam installed centerline question - 11/03/10 01:32 AM
Quote:
Your engine will be ADVANCED.
The intake valve opens earlier and in turn will close earlier. Since it closes ABDC that's a hair more compression the motor will make. Likewise the exhaust valve will open sooner, releasing combustion pressure sooner. All this equates to a loss of power.
This is what you meant to say?
On a serious note.......i agree , ex valve opening earlier could net a loss in power dependant on compression ratio.
Posted By: RapidRobert
Re: Cam installed centerline question - 11/03/10 01:54 AM
yes it's confusing as a smaller # ie 105 vs 108 means sooner (advanced) as 5 o'clock is sooner than 8 o'clock. the intake valve reaches peak lift at 105 deg past TDC compression (which is sooner) than if it reached it at 108 deg past TDC compression (& therefore closes sooner). As said it shifts the power band lower & reduces the valve to piston of either the intake or ex valve (I forget which one). Cams I've advanced (street) which you'd be doing (to 105) have always benefitted from it (more torque)
Posted By: 602heavy
Re: Cam installed centerline question - 11/03/10 02:02 AM
Quote:
yes it's confusing as a smaller # ie 105 vs 108 means sooner (advanced) as 5 o'clock is sooner than 8 o'clock. the intake valve reaches peak lift at 105 deg past TDC INDUCTION stroke (which is sooner) than if it reached it at 108 deg past TDC INDUCTION stroke (& therefore closes sooner). As said it shifts the power band lower & reduces the valve to piston of either the intake or ex valve (I forget which one). Cams I've advanced (street) which you'd be doing (to 105) have always benefitted from it (more torque)
Posted By: dgc333
Re: Cam installed centerline question - 11/03/10 12:55 PM
Another thing to keep in mind is many cams are ground with advance built into them, that is when installed dot to dot. So if that cam recomended 108 centerline is combined with a 112 degree lobe sepration angle then there is 4 degrees of advance already in the cam. When people refer to installing the cam straight up it means that to your cam the centerline would be 112 (straight up is not dot to dot as many folks assume). The confusing thing here is centerline is expressed in crank degrees and lobe seperation is expressed in cam degrees. The crank turns twice for each revolution of the cam so to convert lobe sepration to crank degrees double it and divided by two for the straight up centerline or straight up centerline = lobe seperation angle.
If you install it at a 105 then you will be 7 degrees advanced (as a comparision one tooth off on the cam sproket is 9 degrees on a 40 tooth cam sprocket). The typical rule of thumb is if you need to advance/retard the cam by more than 5 degrees you selected the wrong cam.
Advancing the cam will tend to improve low/mid range power and retarding it will improve high end power.
If you install it at a 105 then you will be 7 degrees advanced (as a comparision one tooth off on the cam sproket is 9 degrees on a 40 tooth cam sprocket). The typical rule of thumb is if you need to advance/retard the cam by more than 5 degrees you selected the wrong cam.
Advancing the cam will tend to improve low/mid range power and retarding it will improve high end power.
Posted By: GomangoCuda
Re: Cam installed centerline question - 11/03/10 06:49 PM
Quote:
double it and divided by two
How long has it been since you had a basic math class?
Posted By: chache876
Re: Cam installed centerline question - 11/03/10 07:13 PM
Heres a somewhat related question about cam timing...
If I have an adjustable timing chain with multiple keyways on the crankshaft gear, and they are marked 0, +1, +2, +3, -1, -2, -3, etc...
Lets say I have a lobe separation angle of 106*
If I set the timing gear so that it is in the +2 slot, does that mean I am advancing the camshaft 2 degrees so that its now 104* or does that mean that I am adding 2 degrees to the 106* number? 106+2=108?
If I have an adjustable timing chain with multiple keyways on the crankshaft gear, and they are marked 0, +1, +2, +3, -1, -2, -3, etc...
Lets say I have a lobe separation angle of 106*
If I set the timing gear so that it is in the +2 slot, does that mean I am advancing the camshaft 2 degrees so that its now 104* or does that mean that I am adding 2 degrees to the 106* number? 106+2=108?
Posted By: 602heavy
Re: Cam installed centerline question - 11/03/10 07:40 PM
Quote:
Heres a somewhat related question about cam timing...
If I have an adjustable timing chain with multiple keyways on the crankshaft gear, and they are marked 0, +1, +2, +3, -1, -2, -3, etc...
Lets say I have a lobe separation angle of 106*
If I set the timing gear so that it is in the +2 slot, does that mean I am advancing the camshaft 2 degrees so that its now 104* or does that mean that I am adding 2 degrees to the 106* number? 106+2=108?
+ advance
- retard
'lining up the dots' is a no no , the only accurate way would be to use a degree wheel , some of those crank/cam gears are not always accurate.
Posted By: dgc333
Re: Cam installed centerline question - 11/04/10 07:24 PM
Quote:
Quote:
double it and divided by two
I know exactly what I said, in my 30+ years as an engineer I have found that sometimes it helps to make things clear to state the obvious. I could have just said; "straight up centerline = lobe seperation angle" but I wonder how many more folks will remember why that is true because I added the silly little math expression.
Posted By: RapidRobert
Re: Cam installed centerline question - 11/04/10 09:27 PM
Quote:I'm w you here as cam theory is (sort of) Greek to me & I need it (the obvious) spelled out so I can grasp it.
I have found that sometimes it helps to make things clear to state the obvious.
Posted By: 383man
Re: Cam installed centerline question - 11/04/10 10:51 PM
Quote:
Heres a somewhat related question about cam timing...
If I have an adjustable timing chain with multiple keyways on the crankshaft gear, and they are marked 0, +1, +2, +3, -1, -2, -3, etc...
Lets say I have a lobe separation angle of 106*
If I set the timing gear so that it is in the +2 slot, does that mean I am advancing the camshaft 2 degrees so that its now 104* or does that mean that I am adding 2 degrees to the 106* number? 106+2=108?
Lobe seperation angle is not the installed centerline. Lobe sep angle is ground into the cam and cannot be changed. The installed centerline is where the cam grinder reccomends to put the intake centerline for best performannce. Ron
Posted By: 426runner
Re: Cam installed centerline question - 11/11/10 02:27 PM
Another related question... It is always recomended to check the installation of the cam for the proper centerline as called for by the manufacturer. Most all write-ups or videos that show the process end up with the CL coming out correct. Mine didn't. My installation calculated out to 105 instead of 108 like the card said it should. Why would this happen? What factors could contribute to the cam not being as the manufacturer says it should be out of the box? And yes, there were 2 of us there during the degreeing process and we did it over and over and came up with the same 105 every time. 
Posted By: RobX4406
Re: Cam installed centerline question - 11/11/10 06:33 PM
Quote:
Another related question... It is always recomended to check the installation of the cam for the proper centerline as called for by the manufacturer. Most all write-ups or videos that show the process end up with the CL coming out correct. Mine didn't. My installation calculated out to 105 instead of 108 like the card said it should. Why would this happen? What factors could contribute to the cam not being as the manufacturer says it should be out of the box? And yes, there were 2 of us there during the degreeing process and we did it over and over and came up with the same 105 every time.
Timing chain set variances, cam being ground slightly off, could be a couple issues to change the installed centerline.
Posted By: Dodgem
Re: Cam installed centerline question - 11/11/10 06:52 PM
It's called the stacking effect. the key way on the crank may be of a bit. the key way in the bottom gear may be off a bit, the dowel hole in the top gear may be off a bit and the dowel placement in the cam may be off a bit as these things are less than perfect.
sometimes it stacks up to 10 or more degree's off.
I would leave your cam where it is you will like it with a tad more advance!