Hot rodding the HEI distributor
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This article deals primarily with older-style non-computer controlled [[HEI distributor]]s. This is because there is so much performance left in them vs. stock AND since many people have ditched the computer in their 3rd gen cars and gone with a totally non-computer controlled engine. Please note: All carbureted V8 F-bodies since 1981 came from the factory stock with a computer controlled, internal coil HEI distributor. Most Fuel Injected 3rd gen V8s use a modified version of the HEI known as a “divorced coil HEI” (these have the small cap with an integrated magnetic trigger - usually found on GM TBI engines). | This article deals primarily with older-style non-computer controlled [[HEI distributor]]s. This is because there is so much performance left in them vs. stock AND since many people have ditched the computer in their 3rd gen cars and gone with a totally non-computer controlled engine. Please note: All carbureted V8 F-bodies since 1981 came from the factory stock with a computer controlled, internal coil HEI distributor. Most Fuel Injected 3rd gen V8s use a modified version of the HEI known as a “divorced coil HEI” (these have the small cap with an integrated magnetic trigger - usually found on GM TBI engines). | ||
| − | A word first about those internal coil computer controlled HEI distributors: Computer controlled versions work basically the same as the old non-computer versions except that they don't have any mechanical advance mechanisms inside them -- the ECM determines the advance curve electronically. Other than buying an aftermarket performance chip for the ECM or buying the proper hardware & software to burn a new chip, there is NO WAY to change the advance curve of a computer-controlled HEI distributor- timing is controlled ENTIRELY by the ECM’s programming! The only change you can make in the advance curve, is to manually advance the base timing (usually worth a little HP by itself). Check your GM service manual for the correct way to set the base timing for your particular engine/year. If you have a computer controlled distributor in your car right now you can’t do much to increase performance other than to make sure it is correctly communicating with your car’s ECM and upgrade the coil to a better unit. This is not a bad thing -- it leaves funds available for parts that WILL make the car faster! | + | A word first about those internal coil computer controlled HEI distributors: Computer controlled versions work basically the same as the old non-computer versions except that they don't have any mechanical advance mechanisms inside them -- the ECM determines the advance curve electronically. Other than buying an aftermarket performance chip for the ECM, or buying the proper hardware & software to tune and burn a new chip, there is NO WAY to change the advance curve of a computer-controlled HEI distributor- timing is controlled ENTIRELY by the ECM’s programming! The only other change you can make in the advance curve, is to manually advance the base timing (usually worth a little HP by itself). Check your GM service manual for the correct way to set the base timing for your particular engine/year. If you have a computer controlled distributor in your car right now you can’t do much to increase performance other than to make sure it is correctly communicating with your car’s ECM and upgrade the coil to a better unit. This is not a bad thing -- it leaves funds available for parts that WILL make the car faster! |
DON’T USE A COMPUTER CONTROLLED DISTRIBUTOR IF YOU HAVE DITCHED THE ECM OR ARE RUNNING WITHOUT ONE!!!! You will get NO ignition timing advance AT ALL from the computer-controlled distributor, plus lousy performance and lousy mileage. If you have disconnected the 4-wire ECM connector going in the side of the distributor or the wiring between the ECM and the distributor is damaged you will, again, get no advance (and a check engine light) Yes, you can remove a non-computer controlled HEI and drop an old-style mechanical advance distributor in its place -- it will physically bolt right in. But it will cause the ECM to throw a code because the ECM looks to make sure the computer-controlled portion of the distributor is out there every time you start the engine. Once you begin to take things out of the ECM’s control you pretty much have to go all the way with it -- replace both the computer-controlled distributor, the computer controlled carb (Qjet) and deactivate the check engine light. | DON’T USE A COMPUTER CONTROLLED DISTRIBUTOR IF YOU HAVE DITCHED THE ECM OR ARE RUNNING WITHOUT ONE!!!! You will get NO ignition timing advance AT ALL from the computer-controlled distributor, plus lousy performance and lousy mileage. If you have disconnected the 4-wire ECM connector going in the side of the distributor or the wiring between the ECM and the distributor is damaged you will, again, get no advance (and a check engine light) Yes, you can remove a non-computer controlled HEI and drop an old-style mechanical advance distributor in its place -- it will physically bolt right in. But it will cause the ECM to throw a code because the ECM looks to make sure the computer-controlled portion of the distributor is out there every time you start the engine. Once you begin to take things out of the ECM’s control you pretty much have to go all the way with it -- replace both the computer-controlled distributor, the computer controlled carb (Qjet) and deactivate the check engine light. | ||
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