Cam timing
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Instructor
Joined: Dec 2005
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From: SoCal California
Cam timing
I was wondering when a cam manufacturer states that a cam has 4* of advanced timing built into the cam, does that mean if you set your initial timing mark @ 2* btdc, you are actually setting the timing at 6* btdc?
Burning Brakes
Joined: Jun 2006
Posts: 1,096
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From: Baltimore MD
Originally Posted by Achilles
I was wondering when a cam manufacturer states that a cam has 4* of advanced timing built into the cam, does that mean if you set your initial timing mark @ 2* btdc, you are actually setting the timing at 6* btdc?
The reference to timing regarding a camshaft is exactly that...CAM TIMING. To remain simple, that means how soon or late the valves open. I beleive "technically" that cam manufacturers, like Comp Cams, state that their cams are ground 4 degress advanced. They make no mention of "TIMING"...
IGNITION TIMING has ZERO to do with camshaft timing...in other words, cam timing has no effect on ignition timing at all...
If your car calls for 6* base ignition timing, then that is what it is set at regardless of how the cam timing is set up.
Advancing cam timing usually helps bottom end, while retarding it usually adds top end...cam timing is changed by using a multi-keyway timing gear...
Last edited by rel3rd; Nov 21, 2006 at 08:02 PM.
Thread Starter
Instructor
Joined: Dec 2005
Posts: 141
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From: SoCal California
So basically, without getting too deep into a state of confussion, when installing a cam that has 4* built into it the timing marks on the crank & cam sprockets are still set straight up as normal.
Burning Brakes
Joined: Jun 2006
Posts: 1,096
Likes: 28
From: Baltimore MD
Originally Posted by Achilles
So basically, without getting too deep into a state of confussion, when installing a cam that has 4* built into it the timing marks on the crank & cam sprockets are still set straight up as normal.
...and when you get to the setting of the ignition timing part of the job, you'd set it the same as you would with your stock camshaft...one has no effect on the other...period.
Safety Car
Joined: Apr 2005
Posts: 3,624
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From: Dale City VA
It does not have anything to do with the distributor timing.
It means the camshaft intake centerline is ground 4*advanced from the lobe seperation. So if you have a camshaft that has an advertised L/S of 110* and you put the timing chain dot to dot (straight up) the intake centerline should measure 106* and the exhaust centerline should measure 114*,
Like wise if you had a camshaft ground with 0* advance it would measure 110* intake centerline and 110* exhaust centerline.
Cam grinders have been grinding in a preset amout of intake centerline advance for decades. Makes it easier for engine builders to install the cam at the best location for peak performance. How much advance (if any) depends on the intended application.
Will
It means the camshaft intake centerline is ground 4*advanced from the lobe seperation. So if you have a camshaft that has an advertised L/S of 110* and you put the timing chain dot to dot (straight up) the intake centerline should measure 106* and the exhaust centerline should measure 114*,
Like wise if you had a camshaft ground with 0* advance it would measure 110* intake centerline and 110* exhaust centerline.
Cam grinders have been grinding in a preset amout of intake centerline advance for decades. Makes it easier for engine builders to install the cam at the best location for peak performance. How much advance (if any) depends on the intended application.
Will
