so your saying that not having 12 volts is frying the module?  this doesnt explain the acute problem though, how could it just start happening. well i ran a wire to a switch and a constant 12 vlt power source, so i will see how this works, im going to try it when i get the new distriutor, cause i burned up all 3!  ill keep you informed, but let me know what you think about this idea. also..should i run different springs(lighter) in the dist with the cam and torque converter i have?  

You might find it less expensive to replace the internal module than the entire distributor.

When you say burned up the distributor, what exactly do you mean?

Is the module smoked?
Is the rotor and or cap smoked?
Is the coil smoked?
Help me out here, is anything else smoked?
Are you sure you're not using Lucas parts?

Have you been reusing parts like the coil or anything else from one to the other.

Electronics don't care for low, high, or shifting voltages. We need to figure out what the line voltage is on this car and specifically what it is where power is going into the distributor.

Does this HEI use the coil in the cap or is it the later version that goes back to an external coil? If the latter, is the coil the correct type/model for the HEI?

I think you said this was an Accel or MSD? Can you correct me and give me model numbers so I can hunt down the correct specs and get back to you? Some after market HEI's and HEI components are sold to replace points directly, they will operate on 12 volts cranking and 9 volts running. If used with 12 volts all the time they'll go up in smoke eventually. Other aftermarket HEIs or HEI components are made to replace OEM HEIs, these will accept the factory 12 volts operating all the time as the voltage source. They don't care to operate on 9 volts and will eventually crap out. So if your mixing types or parts from types you can get into trouble. Too make it more fun HEIs sold to replace point systems can be converted to a full 12 volts with a different coil and module, so you've got to know the part numbers of darn near everything to make sure you've got parts that are matched.

I don't see any value in messing with springs or changing base timing settings, lets get this problem licked before we go off and add more complexity.

I'm in the process of unplugging for the evening, I'll be back on line Friday morning, unless I can successfully wrestle the home link from my wife tonight, she supprorts a global activity and goes intermittantly 24/7 so getting a data link at home isn't easy. It's just so fricking fun to have her talking on her Blue Tooth at 2:30 in the morning from bed, yeah she sleeps with the thing in her ear. Welcome to the future!

Bogie

Bogie  

Most auto parts stores have a machine they plug the module into for testing. It simulates the module running the ignition system. I worked at Autozone while in college, we had one there. It's really simple, only takes a few seconds to test.  

well the rotor and cap seem to look fine, the dist itself seems fine, i think that its frying the module somehow, not sure, i will test the module and see what i come up with, so....when the new dist comes then ill hook it up to the new wires i run and see what i come up with, snds ok doesnt it?  

Before you put the new one in, check the voltage, that way you don't risk frying the distributor.

Sounds like the module's getting too much power, if it was an undervolt like suggested earlier, the module just wouldn't fire, it wouldn't be fried. I've seen some points-to-HEI conversions where they still use a ballast resistor to keep surges and too much power form frying the ignition. Measure your voltage, see where it's at, if too much then you should consider installing a ballast resisitor. The original one might still be mounted on the firewall. If not, you can go to most auto parts stores, they still sell them for about $10.  

same thing happend again...  

Lets go back over configuration. The HEI is whose? The module has a part number, what is it? What is the coil? Is this a coil in cap HEI or seperate coil?

What is the input voltage? Is this different between start and run positions?

What are the plug wires? What are the plugs? What is their gap?

Can you drop back to a points distributor for a test?

Are you running dual batteries on this truck?

What is the B+ line voltage, I'm trying to see if the alternator is putting too much voltage in the circuits?

Bogie  

their jegs powr wires, ac delco plugs, i dont have a points distributor, so i cant readily do that, im going to have to test the voltage going in, where should it be?  and whats the B+ thing.  

"B+" is the term used for electrical system line voltage. Nominally in yours it should be from 12.5 to 14.5 volts. With the engine not running system voltage should be battery voltage which should be close to 12.5 volts. With the engine running fast enough for the alternator to be charging this shouldn't be lower then battery voltage nor higher than 14.5. The lower voltage would show the alternator or regulator is not keeping up to power consumption demand. Higher than 14.5 volts would show that the regulator is not limiting alternator output. This would apply higher than design limit voltages in the system and things that are voltage sensitive will start to fry. This is one of the things I'm concerned about with your situation.

I was hoping you would give me a part number description of what you're using for parts. What I'm trying to figure out is whether or not the parts are electrically compatible.

Some HEI conversion distributors or replacement internal components are designed to use the lower voltages of a point’s distributor; others are designed to accept the nominal 12 volts. There are three different pin outs of HEI modules, I'm trying to see which you've got and is it correct for your situation.

The coil needs to be impedance matched to the module, this kind of potential mismatch is less of a problem with the coil-in-cap configuration assuming that the module is correct. It can be a big issue with remote mounted coil HEIs as the chance for getting an incompatible coil is much higher as there are so many choices. Of course there is always the possibility of a manufacturing error or failure within the coil as well as the mismatch possibilities.

I wanted to know the type/brand of plug wires and plugs to see if there was excessive or insufficient resistance in the wires. A similar want to know about the whether the plugs are resistor type or not. Also what is the gap? All this goes back to how hard the coil has to work.

I'd like to see 2 voltage tests, 1 being line voltage, what I referred to as B+ with the engine turning about 3000 RPM to insure the alternator is producing what ever it’s producing. The other is the voltage on the wire going into the distributor. Not being able to see your set up, if you swapped from points to HEI you had to move a wire that used to supply voltage to the coil to the distributor. With points the hot B+ went to the + terminal of the coil, a wire came from the - terminal of the coil to the distributor where it connected to the points terminal and the points supplied a switch to ground with a capacitor on the side to soak up and smooth the voltage that causes arcing across the points. Points have fairly big arcing problems with 12 volts so what the factory did was to use two power sources for points. For a strong spark while cranking they ran a wire at a battery voltage during cranking, actually B+ voltage drops to about 10.8 volts during cranking since the starter is such a huge amperage sink. Then for running, when you release the key switch from start position to run the connection for B+ voltage is disconnected and a new connection thru a resistive wire or a resistor is made that supplies about 6 to 9 volts to the coil. When you installed the HEI you probably rerouted the old + coil wire to supply voltage to the HEI. When the factory went to HEI, they did away with the different voltages for start and run as burning points was no longer an issue. They went to a simple 12 volt system for HEI. But the aftermarket has supplied distributors meant for point’s replacement that will operate either on the original points wiring or with other models that operate with a full 12 volts. There are modules and coils unique to each out there. I'm trying thru part numbers to figure out which you've got.

I talked about coil failure or manufacturing errors. Electrical systems are highly interdependent; a problem in one place may show up as a failure someplace else. So these things can be tricky to figure out exactly what component is causing the problem. Sometimes this can be several components that have slightly off operating parameters where any one isn't a problem, but all together there is. So thinking about the coil as a major force in the system, if it's out of whack someplace the problems this causes can comeback to smoke the module because the module is the physically weaker of the two parts. So it keeps looking like the module is at fault when the actual problem resides with the coil.

The fact that you can put in a new module and it runs fine for a while is telling me that something in this system isn't right. Whether that's too much or too little input voltage. Whether it's a module whose contacts aren't correct for how the system is wired. Perhaps there's an impedance problem with the coil, or some other issue inside it due to a failure or manufacturing error. Possibly the plug wires and or the plugs have too much or too little resistance even the plug gap being too wide can cause the coil to work too hard. Or whether it's a series of these problems not being quite right enough that gang up over time to smoke the module.

Whatever is going on, the problem seems to have a time element going from functioning fine for a short while then taking out the module. So it's an effect that probably causes the module to heat up with time till it becomes so hot it fails.

A test using a points distributor really is intended to see if the engine will run for a while and if this is an electrical problem on the car side of the wiring will it eventually take out the points or coil. So the points give you some run time to check out the chassis electrical system.

Anyway, what little long distance diognostics I can do, require part number specific information and some test data to help me. I wonder what it would cost to Fed Ex the thing to Seattle where I could look at it, hummm?

Bogie  

Hi guys, I just joined up to get in this discussion...I've been watching this forum for awhile and decided it was time to join as there is a wealth of info here! Anyways, I'm wrasslin with the identical problem with my 355 in a 1984 GMC 4x4.

Here's the situation: I was drivin down the road about 2 yrs ago and there was a sudden electical surge and the truck died. I figured the regulator on the alternator packed it in so I replaced the alternator and also had to replace the module (stock hei) to get 'er runnin again. A couple of months later the module packed 'er in again, so I replaced it again. Well, a couple of months later the module fried again. This time I replaced the entire dizzy with a Mallory hei. SHe ran fine for probably 6-7 months and the module fried again, so I replaced it and it ran fine for another 6months.

Now, a couple of weeks ago, the module went again so I replaced it started it up and it lasted about 5-10 minutes. Replaced it again and same thing only lasted about 5 minutes. So, it went from blowing modules every few months to blowing them in 5 minutes.

What in the *** is going on here...it seems like the regulator may have been shot since the get go with this alternator and now its completely shot. Whaddya think?

Biglong: have you sorted out your problem yet?

Chev  

Back to you guys, also make sure all connections between battery and vehicle are tight and clean. That includes ground straps.

Pull the battery and take it to a shop that can put a load test on it, I'm searching for an intermittent internal short that may be making the alternator surge the line voltage. This often goes undiagnosed till you test the battery with a load. You can do the same thing, well close to the same thing as you can't duplicate the starter load, but by running all lights and accessories you can load the electrical system to see how the voltages react. The alternator needs to hold the line voltage between 12.5 and 15 volts. This should be steady as loads are switched on or off. Voltage less than 12.5 can't keep the battery charged. Voltage above 15, actually about 14.8, will start to fry things. Having an amps reading is also useful during this test.

Bogie  

yeah i did it was a bad ground for the coil on the dist.  

Have you set the 1 piston at top dead center and checked were the rotor is pointing if it is pointing to the number one plug or if your time chain has jumped and is troughing your timing off. Also like everyone else have you checked to make sure you are getting spark. I think I would check the position of the of 1 at tdc and check to see were the rotor is pointing and go from there.  

i am not dumb, i did check that, that was not the problem i just said i figured it out.  

Dumb enough to keep buying 3 or 4 (I lost count) completely new distributors and frying the module, which can be replaced. Distributors themselves dont get fried, the electrical components do, just in case you did'nt know.