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Old 04-05-2010, 01:46 PM
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Initial timing

In the past, using points ignitions, I found that by positioning the crank at the number one firing position, having ignition on, and rotating the distributor I could determine the opening of the points by looking for spark across the (removed) plug gap, and hence a very accurate inital timing position at which to lockdown my distributor. Never had to adjust more than a degree or two after initial start up. The real advantage was that the engine would never backfire, or even sputter much with this technique. You just needed to be sure you rotated the distributor body opposite the normal rotation of the rotor until the plug fired.

I tried this with my HEI, and got nowhere. Does the HEI require some specific rotational velocity to trigger? Is there a trick to doing this with HEI that I am missing?

Thanks for any suggestions.

Pat M

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Old 04-05-2010, 05:47 PM
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There is no spark going to happen in that air gap, if thats what your asking? No certain rotational speed needed, the magnetic field/pulse triggers the ignition module that triggers the coil, basically.
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Old 04-05-2010, 05:59 PM
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So, are you saying that spark should not be able to jump the plug's air gap when the plug is removed, exposed, and grounded? Seems to me it should. Maybe I wasn't clear, but assuming for the minute that it won't, how can I measure when the coil's primary circuit transitions from energized to de-energized. As I understand, when the coil primary circuit is de-energized, the field should collapse, which is what creates the spark, right? If I can identify this exact point, I can pre-set the timing on the engine before acutally starting it up. I mean, we all know that the distributor doesn't necessarily fire when the rotor is pointed directly to the contact in the distributor cap, so I am trying to find a more sophisticated method of pre-start timing than eye-balling the cap contact's position relative to the rotor. Thanks for any additonal input.

PatM
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Old 04-05-2010, 06:56 PM
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I believe the HEI needs a certain rotational velocity to trigger, like you thought, because it isn't a mechanical breaker point. I have never found the HEI to deliver a spark when the whole housing is turned by hand like can be done with mechanical breaker points.
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Old 04-05-2010, 11:43 PM
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I thought you was talking about seeing some spark in the air gap of the distributor pickup


A/C pulse generators do need some speed to change poles in a certain time, to make voltage. But you should be able to spin distributor fast enough to make it past the strengthening field and weakening field of the air gap(in distributor pick up) to make a signal for the control module. I say spin fast enough, I mean grab the distributor and give it a fast jolt 22.5 or so turn. Seems like it would work, in hypothesis land Also, the ignition module has dwell built into it depending on application. So, I dunno, maybe there is a trick somewhere or some bolt on thingy to achieve preset timing Never tried it myself.

Did they have preset timing at the factory? Or is every car timed once its at operating temp rolling off the assembly line? Probably not the latter, so there probably is a tool to do this. But not sure. Sorry for the lack of info, Good luck
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Old 04-12-2010, 01:05 PM
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Thanks to you both. Turning fast won't help. The idea is to rotate slowly, and when the spark occurs, stop immediately and lock down the distributor. The goal is not to make sure I'm firing the correct plug, but at the correct time. I gather Eric has done this too with points ignitions.

Perhaps if I put an instrument on the coil connections I could figure it out. Does anyone off-hand know the color code of the wires to the pos and neg sides of the HEI coil? If I'm getting votage between ground and the ground wire on the coil and it shuts off at some point, that should be when firing occurs, even if the signal ins't strong enough to fire the plug. Or, will this not work either?

Thanks, PatM
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Old 04-12-2010, 03:10 PM
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I don't think that will work, the magnetic pick-up won't read the reluctor at slow speed, so it won't signal the module to fire the coil. Since there is no mechanical "make or break" like there is with point contacts.
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Old 04-13-2010, 05:28 PM
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Thanks Eric. As I feared.

PAt
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Old 04-14-2010, 09:36 AM
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When installing an HEI distributor I tdc the engine and set the distributor in place in a position that aligns the distributor cap #1 plug wire with the rotor and it always has worked. A small adjustment is needed with engine running. As for standard points there is no need to observe a high tension lead, use a test light at the points. When the points are lifted rotating the distributor the light will light up, thats the same position you were describing.
Bill
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