Hot rodding the HEI distributor
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This will be covering the 4-pin HEI module. There were also 5- and 7-pin modules used on computer-controlled applications, however they do not generally lend themselves to non-computer-controlled high performance applications. | This will be covering the 4-pin HEI module. There were also 5- and 7-pin modules used on computer-controlled applications, however they do not generally lend themselves to non-computer-controlled high performance applications. | ||
| − | The module is the electronic controller that takes the place of breaker points. It is located under the distributor cap secured by a pair of screws. One of these screws also acts as a ground path. The module will have four wires going into it (two per side). The module senses the magnetic pickup signal from the magnetic pickup assembly and uses this signal to know when to trigger the coil. The module also controls how much "dwell" the coil receives between firings. | + | The module is the electronic controller that takes the place of breaker points. It is located under the distributor cap secured by a pair of screws. One of these screws also acts as a ground path. The module will have four wires going into it (two per side). The module senses the magnetic pickup signal from the magnetic pickup assembly and uses this signal to know when to trigger the coil. The module also controls how much "dwell" the coil receives between firings. A Delco module is a good choice for street/performance applications and is preferred over an auto parts store non-GM/Delco replacement, possibly unless it's a performance replacement. |
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| + | There have been reports of various quirks associated with some aftermarket modules, so research them beforehand. | ||
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| + | From "yeti" @ yellowbullet.com: | ||
| + | <blockquote> | ||
| + | The HEI modules vary the dwell to eliminate the need for a ballast resistor. This prevents the coil from overheating at low engine speed when a fixed dwell system would leave the coil turned on so long as to over-saturate it and cause excess heat.<br><br> | ||
| + | The actual “Genuine GM” module controls the dwell by monitoring the signal from the pickup with an R/C circuit. Many aftermarket modules accomplish dwell control by measuring the amperage to the coil and cut the dwell to limit it to a preset amount. “High performance” modules have a higher amperage cut-off point to “optimize high RPM performance”. This can result in a situation where if a vehicle has low voltage or high resistance in the primary wiring to the coil, the module will increase the dwell time to the maximum, which approaches 45º and allows no time for the spark to burn. (Sort of an electronic version of "the rubbing block is worn out and the points are closed up”.)<br><br> | ||
| + | Old points vehicles had approximately 30° of points closed time, which made 15° available for the spark to burn. The coil can't discharge when the “points” are closed, mechanical or electronic, because when they are closed it is grounded. | ||
| + | </blockquote> | ||
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| + | ====Module part numbers==== | ||
| + | Some part numbers for a stock-type "990" series module: | ||
| + | *ACDelco D-1906/GM p/n 10482820 (used in the GM ZZ4 crate engine) | ||
| + | *Standard Ignition/Bluestreak p/n LX-301 | ||
| + | *Borg Warner CBE4 | ||
| + | *Echlin TP-45 | ||
| + | *Standard LX-301 | ||
[[File:HEI modules1.jpg|frame|left|If looking for an HEI, choose one that has the 4-pin module seen at upper right, above. The other modules all require an ECM to function correctly.]] <br style="clear:both"/> | [[File:HEI modules1.jpg|frame|left|If looking for an HEI, choose one that has the 4-pin module seen at upper right, above. The other modules all require an ECM to function correctly.]] <br style="clear:both"/> | ||
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