HEI ignition

Depends on how it was wired. This was GM's first attempt at electronic ignition. It was a nice system, but it was designed to be repaired by replacing the entire distributor. Mechanics of that era had a hard time understanding alternators and electronic ignition systems, (both Chrysler innovations). Today we realize these were real simple once they were understood. GM likes to build their cars with large assemblies. They go together quickly on the assembly line, but owners have to buy the whole unit to get the one part they need.

That is an advantage in your case because the entire modification involves dropping in the distributor and connecting one 12 volt feed wire. The entire ignition system, except for the spark plugs and wires, is built into the assembly. Where you might run into trouble is the points system had a ballast resistor in series with the ignition coil. That must be eliminated if you use that wire to feed the HEI distributor. To add to the confusion, that resistor could be a resistor wire hidden in the wiring harness.

The way to tell if you have a resistor in the harness is to disconnect that twelve volt feed wire from the distributor, turn the ignition switch on, then measure the voltage on that wire. You will find full battery voltage. For this sad story, we will say that is 12.6 volts. Now also connect a test light alongside the voltmeter and see what the meter reads. If there is a resistor in the harness, the current flow going to the test light will cause some voltage to be dropped across it, so what you see with the meter will drop a little. That might only be a few tenths of a volt. To be really sure, use some small jumper wires to connect a head light bulb to that wire. Those draw about five amps. That much current will cause a very large voltage drop across a resistor wire and the bulb will not be very bright.

If the voltage stays the same when you connect the test light or the head light bulb, there is no resistor that needs to be removed.

The first version of this system had the normal mechanical and vacuum advance built in like all other distributors had at that time. There was some confusion as to where the vacuum advance hose was supposed to be connected at the carburetor. Most systems put that hose on a port above the throttle blade. That way vacuum advance builds up at higher road speeds when the throttle is open and the blade goes above the port. Vacuum advance provides better fuel mileage by igniting the mixture sooner. Since it takes some time for the gas to burn, it needs to start that burn sooner at higher engine speeds. This system has no vacuum during cranking which makes for easier cranking. Timing is set with the vacuum hose disconnected at the distributor, and plugged.

There were some systems that put the vacuum hose below the throttle blade, or even on a tap screwed into the intake manifold. There still is no vacuum during cranking, so the engine should spin easily, but that vacuum showed up as soon as the engine started running. The thinking was base timing was with vacuum applied, and that is how it is adjusted, then that vacuum advance was lost during acceleration to reduce spark knock. From what I can remember, it seems to me this system was responsible for a lot of real slow, hard cranking when the engine was hot. You would need to find a vacuum hose routing diagram for a car this distributor came from to know for sure how to connect the hose.

Other than checking for full system voltage feeding the distributor, and correct vacuum hose routing, this is just a different way of generating the spark. Stumbles, hesitation, and low power are diagnosed the same way you would with any other engine.

"Acceleration problems" does not say what problem you are having. If you have a Quadrajet carburetor, check for proper operation of the accelerator pump. If you do not have a vacuum advance unit on the distributor, you have one meant to be used with an engine computer. That distributor still generates the timing signal, and its internal module still fires the ignition coil, but that timing signal is seriously-advanced. The computer calculates the mount of delay it wants before telling the module to fire the coil. That is how it adjusts spark timing.

Yup. There is nothing unusual about current flow in that circuit. A 14 gauge wire is sufficient, but often they were 12 gauge because there are other things on the same circuit. Those can include the electric automatic choke heater and anything else that turns on with the ignition switch.

Timing is an issue of the engine's needs, not the distributor. Ignition timing is set the same as for a points distributor. The only difference in systems is how the ignition coil is triggered, not when.

Coil, possibly, but not the ignition coil. Well, I have to think about this a minute. There were enough cases many years ago of a cracked crankshaft position sensor that it became somewhat well-discussed. Due to engine vibration, it would generate extra pulses that the computer interpreted as the time to fire the wrong ignition coil. That caused backfiring.

I was thinking of your pickup coil, but that design really can't crack. A better suspect might be a worn bushing the shaft rides on. Chrysler had trouble with that in their Dakota distributors in the early to mid 90s. The clue was when watching the spark firing with a timing light, the marks were jumping all over the place. You'd feel that as surging and unstable idle speed.

Don't overlook carbon-tracking inside the distributor cap. With such a high potential spark voltage, it can be easy to get a cross-fire to the wrong spark plug wire.

You have to consider fuel problems too. If you're right where the secondaries on a four-barrel, or the power piston on a two-barrel are just starting to open up, a little debris in there will affect performance.

An area of concern that I can't really help with has to do with the curve of the mechanical advance weights in the distributor. Those were eliminated on newer version, then all the timing advance was done by the Engine Computer. I can't even remember how to get down to those weights, but they should be checked for binding or a broken or stretched return spring. I seem to recall those were easily visible when the rotor is popped off. You might be able to duplicate this in the garage, then watch the timing with a timing light. If it advances smoothly and doesn't bounce around, fuel would be a better suspect.

If you have an EGR valve, those must not open at low engine speeds to avoid rough running. Pop the vacuum hose off it and plug it, then see if the problem still occurs. You can also loosen it and slide in a thin piece of metal shim to block it, then drive it that way to see if there's any change.

Don't overlook a plugged fuel filter. If you have a sintered metal filter that looks like a gold porous rock where the line goes into the carburetor, that's a good suspect. Some used a paper element. Either one can plug easily, then volume can't keep up and the level drops in the float bowl. Even a float level that's too low will cause surging and poor performance, but that doesn't change on its own.