Setting total advance with an HEI ignition...
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Joined: Dec 2000
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From: Amsterdam, NY
Setting total advance with an HEI ignition...
Is it necessary to install a weak set of springs in the distributor as I read in one of the tech tips? I originally disconnected the vacuum advance and springs and set the total timing at 36 degrees, it seems fine, no ping plenty of power, but I want to make sure that I set it correctly. Thanks...
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Joined: Feb 1999
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From: Fountain Hills AZ
Re: Setting total advance with an HEI ignition... (wes76)
You should be fine but you can double check by taking a high rpm reading with the springs installed and vacuum disconnected. Some stock set ups don't have full advance until over 4,000 rpm so be sure to check it well past that. If you find that you have more than the 36º, reset it at high rpm.
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Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Setting total advance with an HEI ignition... (wes76)
Wes -
The tech tip you read was probably written by me. Here's the deal....
The HEI centrifugal advance mechanism is limited in its total advance by the geometry and mechanical advantage between the weights and the center cam. With springs of any tension installed, the weights will fling out to a certain point, and then simply run out of mechanical advantage and stop the advance curve. If you remove the springs completely, this limitation does not occur, and you end up with significantly more advance than you would have with a set of light springs installed. Therefore, you end up with a retarded total advance setting and less that peak power.
I found this out during my development of the HEI Curve Kits. On the standard point-style systems, you can successfully remove the springs to set total timing at a very low rpm. I tried this on several HEI units, and kept getting weird timing numbers. After several hours of experimentation on several different cars, I realized that the springs cannot be removed to obtain accurate results. You're really best off installing any set of weak springs during the total timing process - you will get exagerated results if you remove the springs completely on the HEI.
The tech tip you read was probably written by me. Here's the deal....
The HEI centrifugal advance mechanism is limited in its total advance by the geometry and mechanical advantage between the weights and the center cam. With springs of any tension installed, the weights will fling out to a certain point, and then simply run out of mechanical advantage and stop the advance curve. If you remove the springs completely, this limitation does not occur, and you end up with significantly more advance than you would have with a set of light springs installed. Therefore, you end up with a retarded total advance setting and less that peak power.
I found this out during my development of the HEI Curve Kits. On the standard point-style systems, you can successfully remove the springs to set total timing at a very low rpm. I tried this on several HEI units, and kept getting weird timing numbers. After several hours of experimentation on several different cars, I realized that the springs cannot be removed to obtain accurate results. You're really best off installing any set of weak springs during the total timing process - you will get exagerated results if you remove the springs completely on the HEI.
