Crank Trigger and Cam Sync Dist
06-02-2008, 06:17 PM
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Crank Trigger and Cam Sync Dist Hey guys, I touched based with Brady briefly about this and wanted to get a general consensus concerning crank and cam signals. I'm running a BBC with BS3 and to use the SEFI function I need to have a cam signal. Two ways to do it are crank trigger with a cam sync dist. or a crank/cam sync dist. (hall effect). I think the best way would be to have a dedicated cam and crank signal seperate and Brady agrees so it confirmed my thought, so I'm going to run a crank trigger and then a cam sync dist. instead of the hall effect.
Next question is about installing the crank trigger and phasing in the cam signal. You have to find TDC and then rotate back the max number of degrees of timing the motor will see. All the literature I've found throw out 45* as the max timing for a motor and then tack on 5*. So to rotate CCW 50* are you guys using a degree wheel or something else? I thought about using the degrees on the ATI dampner I have and wondered if that was acceptable or not. Also is 45* just generally accepted as max timing or is that based on the motor? Most stuff I have read is between 34-36 so I wasn't sure how important it was to get max timing exactly right.
I haven't fully grasped the cam sync yet in placing the magnet and cap thing yet, but I'm reading and will probably have questions later.
Thanks,
Anthony
Next question is about installing the crank trigger and phasing in the cam signal. You have to find TDC and then rotate back the max number of degrees of timing the motor will see. All the literature I've found throw out 45* as the max timing for a motor and then tack on 5*. So to rotate CCW 50* are you guys using a degree wheel or something else? I thought about using the degrees on the ATI dampner I have and wondered if that was acceptable or not. Also is 45* just generally accepted as max timing or is that based on the motor? Most stuff I have read is between 34-36 so I wasn't sure how important it was to get max timing exactly right.
I haven't fully grasped the cam sync yet in placing the magnet and cap thing yet, but I'm reading and will probably have questions later.
Thanks,
Anthony
06-03-2008, 07:04 PM
#3
If you're doing any type of syncing between the crank trigger and cam a degree wheel is the only way to go, going off the balancer isn't going to be accurate enough you need a big wheel to set it up right and you'll never hit 45* of timing. If a motor uses anything over 38 or 39* it's not working right.
On the 406 SBC motor a friend and I run in his nova we made 780 hp with only 28* of timing, the more efficient the combo the less timing you'll need to make good power. A street strip motor shouldn't need over 34-36*
On the 406 SBC motor a friend and I run in his nova we made 780 hp with only 28* of timing, the more efficient the combo the less timing you'll need to make good power. A street strip motor shouldn't need over 34-36*
06-03-2008, 07:20 PM
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06-04-2008, 09:02 AM
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That's what I figured about the timing, but have either of you installed a crank trigger before? I seriously doubt that guys tear the front of the motor apart install a degree wheel to get to the desired degree mark and then put the motor back together and install the trigger. There has to be an easier way, or a trick of some kind.
06-04-2008, 04:30 PM
#7
If you're trying to find an accurate TDC you can just use the big wheel or go off the balancer and use a stop that goes into the spark plug hole, then go forward till you hit the piston and back go back the other way until you hit the piston and divide the two timing degrees, the middle of the two should be the true TDC.
Maybe you meant something else, I'm getting old young and losing my mind so who knows lol.
Maybe you meant something else, I'm getting old young and losing my mind so who knows lol.
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06-04-2008, 04:42 PM
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No that's not what I meant, I can find TDC just fine. I was referring to moving the piston back down in the hole approx. 45* before TDC on the compression stroke so I can align and install the crank trigger pickup and magnet.
Edit: I just thought of something. You may set your initial timing between 34-36, but then you hook up the vacuum hose to the distributor and it can advance the timing based on what load it sees at the manifold. With that said I think that at a high speed light load you can see quite a bite of timing more than what you set it at initially.
Edit: I just thought of something. You may set your initial timing between 34-36, but then you hook up the vacuum hose to the distributor and it can advance the timing based on what load it sees at the manifold. With that said I think that at a high speed light load you can see quite a bite of timing more than what you set it at initially.
Last edited by ulakovic22; 06-04-2008 at 06:12 PM.
06-05-2008, 10:48 PM
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Timing locked out? Locked out of what? To run SEFI you need a cam and crank signal, crank signal from from a flying magnet and cam signal from a modified distributor with a magnet and pick up. BS3 uses the crank reference, cam sensor and firing order to know which cylinder to fire. All the timing is done by BS3. You must be thinking of a HEI distributor and locking out the vacuum or mechanical advance. Not the same thing.
