This summer Clarence has fried a Pertronix module and three HEIs. Currently it isn't running and it's time I got it fixed. There is still driving to do this year. I had to drive a daily to the Color Run in Quincy last weekend and I don't want to have to do that again. Testing the voltage going to the current HEI shows a low of 11.91v and high of 12.05v. In general the readings run pretty close to 12v. This is by testing the hot lead to the distributor and turning the key to "on". This is without the engine running since it isn't running at all. I've heard that low OR high voltage will destroy HEIs. What tolerance is there? i.e., how high or how low would voltage need to be to harm an HEI. b-t-w; first HEI was a brand-new aftermarket unit and the next one was an original GM HEI that was rebuilt; twice. Next question/situation: I'm thinking that I should rebuild one of the several SBC single point type distributors that I have and replace the HEI. I mean everything replaceable; points, cap, rotor, bushings, et al. I don't know if a points distributor needs a ballast resistor. Does it? I have a ballast resistor that reads 2.2 to 2.3 ohms. Is this a good unit? If I use the points distributor should I install one? This one? Is there anything else that I should be looking into that could be keeping this thing from running? Engine is a crate 350 sbc from Summit Racing with about 10K miles on it. The wiring is a harness from Rebel Wiring that was installed about 8K miles ago. Alternator was replaced at the same time as the wiring. I'm so disgusted with Clarence that it has been sitting idle in my shop for about three weeks. That's where the roll-back delivered it to the last time it quit. I really don't even want to go out there and look at it. I've got to do something though. Don't ask why it had Pertronix or HEI. The story is way too long and it doesn't matter anyway. For the last 32 years it had a GM single point distributor; in this engine and the 283 that used to be in it. b-t-w; (again) I've posted about Clarence distributor problems recently. These: Technical - What are you working on? | Page 113 | The H.A.M.B. Technical - What are you working on? | Page 120 | The H.A.M.B. Technical - What are you working on? | Page 127 | The H.A.M.B. This is the culmination of those problems and I'm hoping to solve this problem once and for all. Thanks in advance for any/all help you folks can give me.
Does the HEI draw any significant current with key on? The voltage that reaches the ignition system needs to be checked under load, if the coil current is off I'm assuming the current will be very small, and a poor connection may not be obvious. You can, for example, replace it with a headlight bulb, this puts a descent load on the system. The need for a ballast resistor depends mostly on the coil used. Have the plug wires and plugs been replaced or at least tested? Bad parts on the high voltage side of the system can damage electronics, among other things. Since it sounds like you've gone through a bunch of parts in short time the real issue probably is something that hasn't been changed.
Hey @atch, sorry to hear about your spark or lack thereof. Of course you know not to run solid core wires with these things. I have 4 MSD plugnplay distributors in my rigs at the moment and couldn't be happier. Simple 12v wiring, no step down like my 71 vette had. That was GM TI (transistorized ignition) and it used 12v to start and then ran on 8v or something. It was the forerunner of the HEI and a PITA! Guess that's why it didn't last too long. What is your plug gap? HEI likes em wide, like 40. There must be something that is being overlooked.
@G-son, Are you saying to put a bulb in series with the wires I'm using to test the voltage to the HEI? Or disconnect from the HEI and test the same hot wire through a light bulb? Or something different? Plug wires got replaced when the first HEI was installed, as you would have surmised. As you well know "regular wires" won't fit the HEI cap. I don't know how old the plugs are. @Bandit Billy, I'll have to pull a couple of plugs next time I'm out there and check the gap.
with a points distributor you need a coil with 1.5 ohms resistance (measured between the + and - terminals) and a ballast resister that has 1.5 ohms. do this and your points will last a very long time... Point ignition systems are the most trouble free ignitions out there. no more rollback trucks needed....
@Moriarity, Thanks. I am pretty much leaning towards going back to points. Now it looks like I have the information I need to do just that. Will whatever fouled up the HEI be a hindrance to points? i.e., will the points be as sensitive to voltage problems? That, of course, is assuming voltage fluctuations caused the existing problems.
Disconnect and replace with the bulb. That way you are sure you are pulling a significant current through the circuit. If it can't maintain a good voltage to the load you know it's bad. And if that's the case you can measure the circuit piece by piece, you'll find the voltage drop where the problem is - i.e. if you have 12V att he battery but only 10V at the load the missing 2V will be across the problem, for example between the load and the ground if it's a poor ground. A good idea to examine or replace those plugs. Not knowing how old they are or what they may have been through I'd prefer to replace them. I wasn't sure what type of wires fit the HEI or your old distributor. There are so many variations of ignition parts, and american V8s aren't very common here, so I can't keep up with what is or has been available for them - or how parts can be modified to work in the wrong place. Electronics are relatively sensitive to several problems and may get damaged because of them, points are not. The problems may of course still cause weaker spark, misfires and such, but actually damaging something is less likely.
One last question, do you have a ground from the engine to the frame? Where does the battery ground attach to?
HEI is big, bulky, and ugly but generally reliable. Three common causes of cap, rotor, or module failure are a missing coil ground (the one in the top of the cap from the coil screw to the harness), bad plug wires with excessive resistance (can burn the rotor under the coil contact), and a lack of heat sink compound under the module. Any one of these can leave you on the side of the road. Movement of the pickup by the vacuum advance over time can cause intermittent failure by breaking the conductor inside the wires. This can manifest as popping or shutdown while driving but may restart after stopping. It can also show as starting up when you hit the key but dieing as the engine settles to an idle. There is another problem that can cause performance issues but usually won't kill the spark and that is mechanical advance wear/sticking.
Perhaps, Mark. I am thinking he has something else CAUSING the problem that may well cause the points to crap out too. A couple have mentioned grounds. They, or lack of them, cause a LOT of electrical problems. Ben
HEI's also need a 14 gauge wire to power them along with heat transfer grease under the modules. Find an original GM 990 module. I pulled a HEI out of truck in a salvage yard 22 years ago, cleaned it up and put into my 250 Chevy, its still running the same factory module that GM installed in 1976. I also still carry the same back up module that I bought new back in '81 that I haven't needed yet.
It does also strike me as odd that it would take out an hei and a petronix/ coil. I would take a look at your voltage regulator. I previously was running an externally regulated alternator and had the regulator go on the Fritz and it wiped out all sorts of stuff. Bought a new one and it was bad out of the box. If you are running a single wire maybe there is a bench test for the regulator in it?
I’ve had a HEI from DUI in my vintage engine land speed race car for over 25 years and could not be happier. Our 56 Ford Y-block has had a Pertronix for 10 years using a stock ballast resistor with out failure. Electronics has its place along with those who don’t want them.
I have had large-body GM HEI distributors in a LOT of cars over a LOT of years and presently have one in my daily. Quite a few years ago I took advantage of "Free Parts Day" at one of our local wreckers and loaded up on factory HEI distributors (pay a set entry fee and anything you can carry out is yours) so I now always carry a complete spare in my trunk at all times as a just-in-case as they are so easy to swap IF there is an issue. I can't believe it would be hard for anyone, anywhere to source a used, factory GM made HEI rather than purchasing some Chinese junk. Other than the wife's G-body (previously owned) getting a complete distributor swap to eliminate an odd stumble, I have found these "ugly" units to be unbelievably reliable. I should clarify, I never bothered to even look for the source of the stumble ... swap in a complete other distributor, problem solved, life goes on. For all I know, it could have been a crusty cap or rotor or something simple. One thing I have noticed is some people saying "make sure you insulate the module with dielectric compound". My understanding is that the product used is not actually dielectric compound but a heat-sink grease used to isolate engine heat from the component. Could using the wrong product help "cook" the module? I'd bet yes. I have no experience with replacement modules or aftermarket HEI's or Pertronix products but, as stated, have a tremendous amount of on-road experience with GM HEI's and I gotta say, I absolutely love 'em for their reliability. The fact that you are blowing through several different styles of distributors in short order suggests to me that the distributors themselves are not the problem. Sure, there is such a thing as bad luck but this is ridiculous. As someone else stated ... do you have sufficient (and clean) grounds? Are you positive your alternator isn't over-charging? Does your new wiring harness include a resistor wire that shouldn't be used with an HEI? These things will run on 12 volts with a single wire coming directly from your battery ... it just doesn't get any simpler.
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