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GM has offered High Energy Ignition (HEI) systems on vehicles starting with selected '74 models. HEI was standard on '75 and newer vehicles. There is now tremendous aftermarket support for HEI, both for individual components and complete ready-to-run distributors. This guide is intended to help you understand the different kinds of HEI, as well as to help you sort out valid engineering from the silly claims primarily coming from keyword-spamming marketers of junky imported components. If you plan to use an HEI in a GM engine family, please check out my guides to GM Small Block engines , Buick, Olds, Cadillac and Pontiac Big Block engines , and Chevrolet Big Block engines .
Kinds of HEI
First, all HEI systems are a kind of electronic ignition, but not all electronic ignitions are HEI. Electronic "conversion kits" to eliminate distributor contact points or complete distributors which don't use GM HEI-style parts inside are NOT HEI systems. "HEI" is a GM/Delco trade name for their particular kind of electronic ignition keeping in mind that the GM design evolved over the years. More broadly, it is used to describe aftermarket "copies" of the GM design, some of which are designed to be used in engine families that did not have GM/Delco-produced HEIs. For example, there are aftermarket copies of the HEI which have distributor housings designed to fit Ford engines.
GM introduced HEI using a novel, "all-in-one" approach for it's V-8 and V-6 engines. This was an improvement of the earlier "Unit Ignition System" used on a very few Pontiacs starting around '72 or so. (The older Unit ignition looks like a Neanderthal HEI, and has the disadvantage that the spark plug wires are also unitized and not replaceable except as a complete set of eight because they are "tied together" at the distributor cap mount. Good luck finding a set now.) The HEI ignition components (Distributor housing including the centrifugal and vacuum advance units, magnetic pick-up and it's "trigger" the reluctor, the electronic module or amplifier, and the ignition coil) were placed in a single assembly. A single battery-voltage power wire supplied all that was needed to run the system. It is incorrect to call the power wire a "12-volt" supply, because when the starter motor is cranking the engine, the voltage may go as low as 9 volts, and as the alternator charges the battery, voltage may be as high as 15.5 volts. The HEI is designed to survive up to about 17 volts. A trigger wire connection was provided so that the HEI could drive an electrically-operated tach. These "all-in-one" units are called the "coil-in-cap" HEIs. The distributor caps (and the aluminum housing they attached to) were made considerably larger than what was traditional, engineers believed that the high voltage potential these ignitions were capable of mandated greater spacing between spark plug terminals to prevent cross-fire. In the early years, the inline engines--4 and 6 cylinder--generally did not use the "all-in-one" design, they had remote-mounted ignition coils with a coil wire connecting the ignition coil to the distributor. The in-line engines did not use a larger-diameter cap and housing. The electronic control module became more complex as emissions requirements tightened over time, and a major revision to the HEI was done in '87 for Chevrolet trucks using Throttle Body Injection (TBI) so the Chevy TBI V-8 and V-6 engines no longer had the ignition coils in the distributor caps, and the caps were no longer of the larger diameter.
The module is the heart of the HEI system, early modules had four electrical terminals: two large ones, for battery voltage input, (labeled "B") and the ignition coil grounding terminal (labeled "C"). There were two smaller terminals for the pickup coil leads to attach to (labeled "W" for white and "G" for green--the colors of the pickup coil lead wires. More on this later. These four-terminal modules are the most common ones, favored for typical "hot-rod" purposes on non-computer-controlled vehicles.
I have seen photos of a three-terminal HEI module, they're listed as NAPA number TP46. I've never held one in my hand. They're VERY rare-but that doesn't mean they're valuable.
There were three different versions of a five-terminal module, and they aren't interchangeable with one another. In each case, the fifth terminal was used to accept a signal that the module processed in order to retard the timing. All the "5-terminal" modules are used with distributors having conventional centrifugal and vacuum advance mechanisms.
The later Chevrolet TBI seperate-coil distributor, along with distributors for some other engines, use an 8-terminal module. Delco sold a marine distributor kit to upgrade older boat engines to electronic ignition, it was called the Delco Voyager Marine Distributor Ignition System. Kits were available for 2.5 and 3.0 liter 4-poppers (P/N 10457090), 4.3 liter V-6 (10457091), Small block Chevy (10457092) and Big Block Chevy engines (10457093). (the only difference between the small block and big block kits is the ignition coil--because of a different mounting bracket) These marine ignition kits relied on the timing curve built into the module for all spark advance. Sadly, these kits have been discontinued. It would be possible, therefore, to run a race-only engine using the modern 8-pin module and no computer, using the timing curve built into the marine module. Because there is no counterpart to vacuum advance, this would be a very poor choice for a street-driven car or truck.
Coil-in-cap
Although all early HEI distributors seem to look alike--aside from the housing changes needed to fit different engine families--there is a tendency for people to think that all the parts inside are the same, too. This is not the case especially in terms of the ignition coils and the pickup coils. Ignition coils and pickup coils should be considered a "matched set", that is, you need to look at the color codes on each part and match the codes to each other, and to the vehicle/engine family the distributor will be used in. Failure to use the appropriate color codes may result in poor starting and misfiring at low speed. The brand names listed are for the ENGINES, not the CARS--a Chevy-designed engine in a Buick car uses the Chevrolet color codes, not the Buick color codes.
For V-8 engines, there are three color codes for the pickup coils:
It has been claimed by others that the difference in the coils has to do with the direction of distributor rotation--that is NOT correct.
Separate coil
With the ignition coil out of the immediate neighborhood of the pickup coil, there is no need to match magnetic polarity. Separate coils are not color-coded. Pickup coils are still matched to the engine family as long as that engine family had a genuine Delco HEI during it's production life.
Best "hot rodding" tricks
4. Assure that the module you are using is at least as good as the stock GM/Delco units supplied since the later '70's. Very early GM modules had problems, but since they're about thirty years old now, there probably aren't too many survivors. GM soon updated the module and it is now quite reliable for performance use. Many aftermarket modules--especially the ones sold based on low price--are inferior. I'd be suspicious of any module that didn't have a well-respected brand name. Delco; Echlin's quality line; and Standard/Blue Streak should all be just fine. There is an "urban legend" about how the HEI doesn't function properly after 4,000 or 4,500 RPM. Not true, provided you have a Delco or better module.
6. GM considered the original '74--'75 HEI to be a "50,000 volt" device. The higher power that the HEI is capable of was the reason for the wider spacing of the spark plug terminals on the cap. So if the aftermarket discount hot-rod parts seller is telling you how great his "50,000 volt coil" is, you can be pretty much assured that it's not one bit better than what GM installed as standard equipment on eleventy-billion cars and trucks over the years. FACT: You will NOT get any more voltage than what it takes to fire the plug. If the plug fires at 8,000 volts, that is all the coil will produce--even if it's sold as a super-gee-whiz performance-car coil.
7. The thin pickup coil lead wires have had a history of failure due to the motion of the vacuum advance. The problem often starts showing itself as the engine dying, then running, then dying, then running, etc. When the vacuum advance moves the pickup coil to a certain position, the broken conductor inside the insulation of the wire disconnects, and the engine dies. When the engine dies, vacuum is reduced, the vacuum advance relaxes--and the broken wire re-connects and the engine runs again.
If this guide has been helpful, please give me a "Yes" vote with the button below. If you have suggestions for improvement, you can contact me through the "My Messages" feature of eBay, by clicking on my user name, and then on "Contact Member". Thanks, all!
Entire contents copyright (C) 2007, 2008 Camino3X2 Feel free to LINK to this Guide in your auctions.
Kinds of HEI
First, all HEI systems are a kind of electronic ignition, but not all electronic ignitions are HEI. Electronic "conversion kits" to eliminate distributor contact points or complete distributors which don't use GM HEI-style parts inside are NOT HEI systems. "HEI" is a GM/Delco trade name for their particular kind of electronic ignition keeping in mind that the GM design evolved over the years. More broadly, it is used to describe aftermarket "copies" of the GM design, some of which are designed to be used in engine families that did not have GM/Delco-produced HEIs. For example, there are aftermarket copies of the HEI which have distributor housings designed to fit Ford engines.
GM introduced HEI using a novel, "all-in-one" approach for it's V-8 and V-6 engines. This was an improvement of the earlier "Unit Ignition System" used on a very few Pontiacs starting around '72 or so. (The older Unit ignition looks like a Neanderthal HEI, and has the disadvantage that the spark plug wires are also unitized and not replaceable except as a complete set of eight because they are "tied together" at the distributor cap mount. Good luck finding a set now.) The HEI ignition components (Distributor housing including the centrifugal and vacuum advance units, magnetic pick-up and it's "trigger" the reluctor, the electronic module or amplifier, and the ignition coil) were placed in a single assembly. A single battery-voltage power wire supplied all that was needed to run the system. It is incorrect to call the power wire a "12-volt" supply, because when the starter motor is cranking the engine, the voltage may go as low as 9 volts, and as the alternator charges the battery, voltage may be as high as 15.5 volts. The HEI is designed to survive up to about 17 volts. A trigger wire connection was provided so that the HEI could drive an electrically-operated tach. These "all-in-one" units are called the "coil-in-cap" HEIs. The distributor caps (and the aluminum housing they attached to) were made considerably larger than what was traditional, engineers believed that the high voltage potential these ignitions were capable of mandated greater spacing between spark plug terminals to prevent cross-fire. In the early years, the inline engines--4 and 6 cylinder--generally did not use the "all-in-one" design, they had remote-mounted ignition coils with a coil wire connecting the ignition coil to the distributor. The in-line engines did not use a larger-diameter cap and housing. The electronic control module became more complex as emissions requirements tightened over time, and a major revision to the HEI was done in '87 for Chevrolet trucks using Throttle Body Injection (TBI) so the Chevy TBI V-8 and V-6 engines no longer had the ignition coils in the distributor caps, and the caps were no longer of the larger diameter.
The module is the heart of the HEI system, early modules had four electrical terminals: two large ones, for battery voltage input, (labeled "B") and the ignition coil grounding terminal (labeled "C"). There were two smaller terminals for the pickup coil leads to attach to (labeled "W" for white and "G" for green--the colors of the pickup coil lead wires. More on this later. These four-terminal modules are the most common ones, favored for typical "hot-rod" purposes on non-computer-controlled vehicles.
I have seen photos of a three-terminal HEI module, they're listed as NAPA number TP46. I've never held one in my hand. They're VERY rare-but that doesn't mean they're valuable.
There were three different versions of a five-terminal module, and they aren't interchangeable with one another. In each case, the fifth terminal was used to accept a signal that the module processed in order to retard the timing. All the "5-terminal" modules are used with distributors having conventional centrifugal and vacuum advance mechanisms.
1. HEI/EMR Electonic Module Retard uses a wire connected to a switch or to an electronic control package. Under certain conditions, the switch or control package will ground the wire, which triggers the retard feature built into the distributor module.
2. HEI/ESC Electronic Spark Control uses a knock sensor and an electronic controller. The knock sensor sends a voltage signal to the controller, which sends a voltage signal to the distributor module, activating the retard feature within the module.
3. HEI/ESS Electronic Spark Selection uses an outboard electronic decoder which receives voltage signals from three sources: a manifold pressure switch, the distributor pickup coil, and an engine temperature switch. The decoder processes the information and provides a voltage signal to the distributor module to adjust the amount of advance/retard.
When vehicles went to full computer control of ignition timing and fuel mixture beginning in '80 or '81, a seven-terminal module was used. This is termed HEI/EST (Electronic Spark Timing) These distributors did NOT have centrifugal and vacuum advance mechanisms, all timing advance was pre-programmed into the computer, using information from the entire array of engine sensors. Base timing could be adjusted, however. A not-common variant of HEI/EST used an additional in-distributor component called a Hall Effect Switch, providing a better signal to the computer at cranking speed than the ordinary pickup coil and reluctor.2. HEI/ESC Electronic Spark Control uses a knock sensor and an electronic controller. The knock sensor sends a voltage signal to the controller, which sends a voltage signal to the distributor module, activating the retard feature within the module.
3. HEI/ESS Electronic Spark Selection uses an outboard electronic decoder which receives voltage signals from three sources: a manifold pressure switch, the distributor pickup coil, and an engine temperature switch. The decoder processes the information and provides a voltage signal to the distributor module to adjust the amount of advance/retard.
The later Chevrolet TBI seperate-coil distributor, along with distributors for some other engines, use an 8-terminal module. Delco sold a marine distributor kit to upgrade older boat engines to electronic ignition, it was called the Delco Voyager Marine Distributor Ignition System. Kits were available for 2.5 and 3.0 liter 4-poppers (P/N 10457090), 4.3 liter V-6 (10457091), Small block Chevy (10457092) and Big Block Chevy engines (10457093). (the only difference between the small block and big block kits is the ignition coil--because of a different mounting bracket) These marine ignition kits relied on the timing curve built into the module for all spark advance. Sadly, these kits have been discontinued. It would be possible, therefore, to run a race-only engine using the modern 8-pin module and no computer, using the timing curve built into the marine module. Because there is no counterpart to vacuum advance, this would be a very poor choice for a street-driven car or truck.
Coil-in-cap
Although all early HEI distributors seem to look alike--aside from the housing changes needed to fit different engine families--there is a tendency for people to think that all the parts inside are the same, too. This is not the case especially in terms of the ignition coils and the pickup coils. Ignition coils and pickup coils should be considered a "matched set", that is, you need to look at the color codes on each part and match the codes to each other, and to the vehicle/engine family the distributor will be used in. Failure to use the appropriate color codes may result in poor starting and misfiring at low speed. The brand names listed are for the ENGINES, not the CARS--a Chevy-designed engine in a Buick car uses the Chevrolet color codes, not the Buick color codes.
For V-8 engines, there are three color codes for the pickup coils:
Yellow tyrap (early) or Yellow plastic connector (later) on the wires. Used on Chevrolet; Cadillac; and Olds engines in Toronado
Blue tyrap (early) or Black plastic connector (later) on the wires. Used on Buick; and all Olds engines except those in Toronados. The lead wires are slightly longer than those used on the "yellow" pickup coil.
Clear or NO tyrap (early), Clear or NO plastic connector (later) on the wires This is identical to the Blue/Black color code, except the wires are even longer to fit a Pontiac distributor.
Sorry, I have NO CONTROL over the size of the photo.
Note the first two coils have green/white wires, the third has white/green wires. Wire lengths are from longest to shortest.
The connectors are, in order, Clear (Pontiac), Black (Buick/Olds), Yellow (Chevy/Cadillac)
The yellow connector is right-side-up, both the other two must be flipped over (wires crossed) to connect to the module. Crossing the wires preserves the electrical polarity while allowing reversed magnetic polarity.
There are two color codes for the in-cap ignition coils:Blue tyrap (early) or Black plastic connector (later) on the wires. Used on Buick; and all Olds engines except those in Toronados. The lead wires are slightly longer than those used on the "yellow" pickup coil.
Clear or NO tyrap (early), Clear or NO plastic connector (later) on the wires This is identical to the Blue/Black color code, except the wires are even longer to fit a Pontiac distributor.
Sorry, I have NO CONTROL over the size of the photo.
Note the first two coils have green/white wires, the third has white/green wires. Wire lengths are from longest to shortest.
The connectors are, in order, Clear (Pontiac), Black (Buick/Olds), Yellow (Chevy/Cadillac)
The yellow connector is right-side-up, both the other two must be flipped over (wires crossed) to connect to the module. Crossing the wires preserves the electrical polarity while allowing reversed magnetic polarity.
Red and Yellow wires Used on vehicles that use the Yellow coded pickup coil.
Red and White wires Used on vehicles that use the Blue/Black, or Clear pickup coils
As a rule of thumb: If the engine has the starter motor on the right (passenger's side), it uses the yellow code parts. If it has the starter motor on the left, it uses the other set. Since Olds Toronados are the only Olds engines with the starter on the right, they use different coils from the other Olds engines. BUICK IS AN EXCEPTION, for reasons I do not know. I have confirmed the color codes and their applications for V-8
engines listed above in Delco Service Bulletin 1.2D-27 dated 12-1-75. Red and White wires Used on vehicles that use the Blue/Black, or Clear pickup coils
It has been claimed by others that the difference in the coils has to do with the direction of distributor rotation--that is NOT correct.
SPECIAL IMPORTANT NOTE #1
These coils may have different color codes, but NONE OF THEM is a HIGH PERFORMANCE/BETTER/FASTER/MORE POWERFUL version of another. You don't get stronger sparks with a yellow-coded set than the others. The ONLY difference is that when you pass an electric current through them, they produce a magnetic field in opposite directions. Note that for the Blue/Black and the Clear color coded pickup coils, the lead wires and the plastic connector (if used) are arranged in such a way that the wires must be crossed in order to connect them to the module. The Yellow-coded pickup coil wires plug in without crossing. This maintains proper ELECTRICAL polarity, while allowing reversed MAGNETIC polarity. And magnetic polarity is only important at low engine speeds, (especially cranking) because of electrical interference from the starter or perhaps the alternator--If the interference is "just right", the module gets a false trigger signal. Using the correct magnetic polarity pickup coil can eliminate the interference, and the correct magnetic polarity ignition coil is needed to match the pickup coil. You "can" mis-match the parts, but don't complain if the engine takes longer to crank or misfires during cranking.
These coils may have different color codes, but NONE OF THEM is a HIGH PERFORMANCE/BETTER/FASTER/MORE POWERFUL version of another. You don't get stronger sparks with a yellow-coded set than the others. The ONLY difference is that when you pass an electric current through them, they produce a magnetic field in opposite directions. Note that for the Blue/Black and the Clear color coded pickup coils, the lead wires and the plastic connector (if used) are arranged in such a way that the wires must be crossed in order to connect them to the module. The Yellow-coded pickup coil wires plug in without crossing. This maintains proper ELECTRICAL polarity, while allowing reversed MAGNETIC polarity. And magnetic polarity is only important at low engine speeds, (especially cranking) because of electrical interference from the starter or perhaps the alternator--If the interference is "just right", the module gets a false trigger signal. Using the correct magnetic polarity pickup coil can eliminate the interference, and the correct magnetic polarity ignition coil is needed to match the pickup coil. You "can" mis-match the parts, but don't complain if the engine takes longer to crank or misfires during cranking.
SPECIAL IMPORTANT NOTE #2
Most parts books list the wrong coils for Olds engines installed in Toronados. Same for people selling "complete" Olds distributors--they don't specify which coils are used; and therefore they're going to be wrong for either Toronados--or--all other Olds applications. MSD, a respected brand, does not sell a red/white HEI in-cap coil as of 14 January '08, only the red/yellow versions. I find this disappointing. For engine families that do not have genuine Delco HEI parts support, I suppose the best you can do is to assure the pickup coil matches the ignition coil--either both coils should be "yellow" codes, or both should NOT be yellow codes, either way. (and perhaps select parts based on which side of the engine the starter is mounted on.)
Most parts books list the wrong coils for Olds engines installed in Toronados. Same for people selling "complete" Olds distributors--they don't specify which coils are used; and therefore they're going to be wrong for either Toronados--or--all other Olds applications. MSD, a respected brand, does not sell a red/white HEI in-cap coil as of 14 January '08, only the red/yellow versions. I find this disappointing. For engine families that do not have genuine Delco HEI parts support, I suppose the best you can do is to assure the pickup coil matches the ignition coil--either both coils should be "yellow" codes, or both should NOT be yellow codes, either way. (and perhaps select parts based on which side of the engine the starter is mounted on.)
Separate coil
With the ignition coil out of the immediate neighborhood of the pickup coil, there is no need to match magnetic polarity. Separate coils are not color-coded. Pickup coils are still matched to the engine family as long as that engine family had a genuine Delco HEI during it's production life.
Best "hot rodding" tricks
1. Replace the high-resistance carbon button under the in-cap coil with a low resistance button from MSD, Crane, Accel, or other sources. (I generally use the Crane button, based only on price.) The stock high-resistance buttons can get so hot that they melt the distributor cap.
2. If you don't want to deal with color coded ignition coils, an "in-cap" ignition coil can be easily replaced with an external ignition coil of your choice, a coil wire to suit, and a readily-available external-coil kit sold by MSD and others.
3. Adjust the centrifugal and vacuum advance curves to best suit your engine. There are adjustable vacuum advance units sold by Crane and others, or just buy a non-adjustable GM or aftermarket vacuum advance that is a good match for your application. Advance cans are sold with a multitude of different part numbers, relating to total advance and the stiffness of the internal spring that determines how fast the vacuum advance operates. Kits are sold having springs, weights, and a center plate to adjust the centrifugal advance. In general, the weights in these kits are too light, and should be immediately thrown into the nearest recycle bin. The springs, and "perhaps" the center plate can be used to good effect. Keep in mind that GM supplied weights of different shapes and sizes, and that the center plate has as much effect as the weights and springs in determining the advance curve--but I do not know of any source still selling an assortment of center plates. Grab 'em from the salvage yard, or fabricate them yourself. (good luck!)
2. If you don't want to deal with color coded ignition coils, an "in-cap" ignition coil can be easily replaced with an external ignition coil of your choice, a coil wire to suit, and a readily-available external-coil kit sold by MSD and others.
3. Adjust the centrifugal and vacuum advance curves to best suit your engine. There are adjustable vacuum advance units sold by Crane and others, or just buy a non-adjustable GM or aftermarket vacuum advance that is a good match for your application. Advance cans are sold with a multitude of different part numbers, relating to total advance and the stiffness of the internal spring that determines how fast the vacuum advance operates. Kits are sold having springs, weights, and a center plate to adjust the centrifugal advance. In general, the weights in these kits are too light, and should be immediately thrown into the nearest recycle bin. The springs, and "perhaps" the center plate can be used to good effect. Keep in mind that GM supplied weights of different shapes and sizes, and that the center plate has as much effect as the weights and springs in determining the advance curve--but I do not know of any source still selling an assortment of center plates. Grab 'em from the salvage yard, or fabricate them yourself. (good luck!)
SPECIAL IMPORTANT NOTE #3
I have seen excessive "hidden" centrifugal advance when the center plate is installed "wrong". That is, you may think you have a normal, proper centrifugal advance, and that it stops advancing at or around 2500--3000 rpm. But if you rev higher, it will begin advancing again at 4000-4500 rpm. That "hidden" advance--perhaps an additional 5--10 degrees--at best will reduce performance and perhaps cause ping--at worst it will destroy your engine. I have seen this on EVERY GM center plate I've checked when the weights are acting on the gently rounded part of the center plate. If you flip the center plate upside down, so the weights act on the dogleg curve part, the advance will positively stop at a given RPM dependant on the weights and the shape of the center plate. The numbers stamped into the center plate may face up or face down. Either way "can" be correct, depending on the direction of rotation of the distributor.
I have seen excessive "hidden" centrifugal advance when the center plate is installed "wrong". That is, you may think you have a normal, proper centrifugal advance, and that it stops advancing at or around 2500--3000 rpm. But if you rev higher, it will begin advancing again at 4000-4500 rpm. That "hidden" advance--perhaps an additional 5--10 degrees--at best will reduce performance and perhaps cause ping--at worst it will destroy your engine. I have seen this on EVERY GM center plate I've checked when the weights are acting on the gently rounded part of the center plate. If you flip the center plate upside down, so the weights act on the dogleg curve part, the advance will positively stop at a given RPM dependant on the weights and the shape of the center plate. The numbers stamped into the center plate may face up or face down. Either way "can" be correct, depending on the direction of rotation of the distributor.
4. Assure that the module you are using is at least as good as the stock GM/Delco units supplied since the later '70's. Very early GM modules had problems, but since they're about thirty years old now, there probably aren't too many survivors. GM soon updated the module and it is now quite reliable for performance use. Many aftermarket modules--especially the ones sold based on low price--are inferior. I'd be suspicious of any module that didn't have a well-respected brand name. Delco; Echlin's quality line; and Standard/Blue Streak should all be just fine. There is an "urban legend" about how the HEI doesn't function properly after 4,000 or 4,500 RPM. Not true, provided you have a Delco or better module.
5. HEI distributors are not that tough to rebuild. The worst part would be installing new bushings, if they were needed.
I would rather have a rebuilt (or even a "good used") DELCO HEI than a brand-new Communist-China derived knockoff copy,
provided that Delco made a housing to fit the intended engine.
6. GM considered the original '74--'75 HEI to be a "50,000 volt" device. The higher power that the HEI is capable of was the reason for the wider spacing of the spark plug terminals on the cap. So if the aftermarket discount hot-rod parts seller is telling you how great his "50,000 volt coil" is, you can be pretty much assured that it's not one bit better than what GM installed as standard equipment on eleventy-billion cars and trucks over the years. FACT: You will NOT get any more voltage than what it takes to fire the plug. If the plug fires at 8,000 volts, that is all the coil will produce--even if it's sold as a super-gee-whiz performance-car coil.
7. The thin pickup coil lead wires have had a history of failure due to the motion of the vacuum advance. The problem often starts showing itself as the engine dying, then running, then dying, then running, etc. When the vacuum advance moves the pickup coil to a certain position, the broken conductor inside the insulation of the wire disconnects, and the engine dies. When the engine dies, vacuum is reduced, the vacuum advance relaxes--and the broken wire re-connects and the engine runs again.
If this guide has been helpful, please give me a "Yes" vote with the button below. If you have suggestions for improvement, you can contact me through the "My Messages" feature of eBay, by clicking on my user name, and then on "Contact Member". Thanks, all!
Entire contents copyright (C) 2007, 2008 Camino3X2 Feel free to LINK to this Guide in your auctions.
Guide created: 10/07/06 (updated 07/22/08)
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