Hot rodding the HEI distributor
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The HEI centrifugal advance is susceptible to wear. Typically the centrifugal advance weights wear their pivot holes into an "oval" or eat a groove into their pivot pins (see green arrows in image below). If an attempt to change the advance curve is made on a distributor that suffers from these problems, the mechanical advance may not work as smoothly as needed. So fix it first or get another HEI to start improvements on; just make sure you are getting the right one for your engine- they were used on ALL makes of GM inline and V6/V8 engines and all look similar. | The HEI centrifugal advance is susceptible to wear. Typically the centrifugal advance weights wear their pivot holes into an "oval" or eat a groove into their pivot pins (see green arrows in image below). If an attempt to change the advance curve is made on a distributor that suffers from these problems, the mechanical advance may not work as smoothly as needed. So fix it first or get another HEI to start improvements on; just make sure you are getting the right one for your engine- they were used on ALL makes of GM inline and V6/V8 engines and all look similar. | ||
| − | Also, the centrifugal advance plate (that rotates on the main distributor shaft as the centrifugal advance moves it), near the top of the distributor shaft sometimes gets gummed up and "sticky," slowing the advance curve and generally preventing the centrifugal advance assembly from working correctly. If your centrifugal advance doesn't "snap" back when you twist the rotor with your hand and let it go then you have this problem. You need to pull the distributor shaft apart and clean everything out, especially up top, before you proceed with upgrades. See the '''[[Hot rodding the HEI distributor#Resources|articles on rebuilding the HEI]]''' below. | + | Also, the centrifugal advance plate (that rotates on the main distributor shaft as the centrifugal advance moves it), near the top of the distributor shaft sometimes gets gummed up and "sticky," slowing the advance curve and generally preventing the centrifugal advance assembly from working correctly. If your centrifugal advance doesn't "snap" back when you twist the rotor with your hand and let it go then you have this problem. You need to pull the distributor shaft apart and clean everything out, especially up top, before you proceed with upgrades. |
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| + | {{Note1}}See the '''[[Hot rodding the HEI distributor#Resources|articles on rebuilding the HEI]]''' below. | ||
===Limiting or locking the mechanical advance mechanism=== | ===Limiting or locking the mechanical advance mechanism=== | ||
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You can run without a vacuum advance but expect your highway mileage to suffer, possibly more. And your plugs can develop carbon deposits within just a few thousand miles. For a race or a weekend street/strip vehicle this is probably no big deal, as long as fresh plugs are installed when needed. For a daily driven street car, using a vacuum advance is always recommended. | You can run without a vacuum advance but expect your highway mileage to suffer, possibly more. And your plugs can develop carbon deposits within just a few thousand miles. For a race or a weekend street/strip vehicle this is probably no big deal, as long as fresh plugs are installed when needed. For a daily driven street car, using a vacuum advance is always recommended. | ||
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| + | {{Note1}} See link for HEI vacuum advance specs under '''[[Hot rodding the HEI distributor#Resources|Resources]]''', below. | ||
===Vacuum advance for the street=== | ===Vacuum advance for the street=== | ||
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*[http://www.rustpuppy.org/ignition2/Ignition%202b.htm GM HEI distributor notes, etc.] | *[http://www.rustpuppy.org/ignition2/Ignition%202b.htm GM HEI distributor notes, etc.] | ||
*[http://www.rustynutscarclub.com/HEI.htm Description of an HEI rebuild] | *[http://www.rustynutscarclub.com/HEI.htm Description of an HEI rebuild] | ||
| − | + | '''''Return to: [[Hot rodding the HEI distributor#Distributor shaft end play adjustment|Distributor shaft end play adjustment]], above''''' | |
| − | + | *[http://www.hotrodders.com/forum/centrifugal-advance-177478.html HEI-type vacuum advance can specs] | |
| + | '''''Return to: [[Hot rodding the HEI distributor#Vacuum advance|Vacuum advance]], above'''''. | ||
| + | *[http://www.corvetteforum.com/techtips/viewsubtopic.php?SubTopicID=115&TopicID=3 GM points-type vacuum advance can specs and info (Lars)] | ||
;Crankshaft Coalition wiki articles<nowiki>:</nowiki> | ;Crankshaft Coalition wiki articles<nowiki>:</nowiki> | ||
*[http://www.crankshaftcoalition.com/wiki/Category:Firing_orders Firing orders] of various engines. | *[http://www.crankshaftcoalition.com/wiki/Category:Firing_orders Firing orders] of various engines. | ||
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