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Old 01-28-2011, 09:05 AM
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Cam Lobe Centerline, what does it mean?

trying to get my head around the basic cam variables.

believe that I can work my way through all of the cam variables, except cam lobe centerline,, I am not speaking of cam lobe separation angle, which is the average of the intake and exhaust cam lobe centerlines.

I have seen the formula and I have seen how the formula gives a number like 102 degrees or 114 degrees for an intake or exhaust centerline,, and that is my question,, what does the degree number relate to,, I think it should be telling me where maximum valve opening is in relation to piston position,, but I am not getting that connection.

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Old 01-28-2011, 10:19 AM
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Old 01-28-2011, 05:21 PM
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To put it simple, cam lobe centerline is the highest point on a cam lobe. Easy to determine on a cam that's very mild and has a almost pointed lobe, but on a radical long duration cam it appears to be at centerline for a longer period. It is an imaginary line through the center of the cam journal to that higest point.
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Old 01-28-2011, 06:17 PM
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yep I agree that the lobe centerline is the highest part of the cam

my question deals with,, if I have 2 cams ,, both with 106 lobe separation angle,,
cam #1 has the intake and exhaust centers both at 106,, so it has a LSA of 106
Cam #2 has the intake lobe center at 102 and the exhaust lobe center at 110,, again, this cam like the first will have a LSA of 106...

but certainly these are not identical cams,,what performance or efficiency difference would on expect to see as lobe centerlines change?
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Old 01-28-2011, 06:26 PM
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Quote:
Originally Posted by DadTruck
yep I agree that the lobe centerline is the highest part of the cam

my question deals with,, if I have 2 cams ,, both with 106 lobe separation angle,,
cam #1 has the intake and exhaust centers both at 106,, so it has a LSA of 106
Cam #2 has the intake lobe center at 102 and the exhaust lobe center at 110,, again, this cam like the first will have a LSA of 106...

but certainly these are not identical cams,,what performance or efficiency difference would on expect to see as lobe centerlines change?
Both these cams are still identical, the only difference is the dowel pin is 4 different in location, i.e. the 2nd cam is ground 4 advanced.

You could make the 1st cam identical to the second (as installed in the motor) by using a timing set with multiple keyways and installing it on the +4 keyway.

Advancing the cam has the effect of lowering the powerband, and retarding the cam raises the powerband up the rpm scale. Not a huge change, 300-400 rpm or so.
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Old 01-29-2011, 07:30 AM
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thanks

that helps,, I had read of advancing or retarding the cam on installation,, but did not put that together with the cam lob centerlines and lobe separation angle changes.
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