Thread: HEI voltage drop ?

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One thing you mite check is the ground strap that hooks to the coil under the cap. I have seen a lot of people with the same problem when it can be as simple as a bad ground.if your hei has been worked on it could be the strap was not even put back on, or the black wire is broken.The engine will still run but will miss at high rpm or under a big load.And if this is the problem, check the leads to the winding on the coil they are probably melted and could short on the field frame.Jeff

I'd go back to where Nitrowarrior was taking you. It sounds like it might be a case of "garbage in, garbage out". If you have a fluctuation in the hot lead voltage then you WILL have a miss on the secondary side.

Voltage fluctuations on electronic motors are worse than on an old fashioned points based system. In both systems when the voltage drops you lose spark immediately (or nearly so). When power resumes it take a bit of time for the electronics version to get it's stuff together again, this stretches the event out and makes it more noticable.

Was the engine miss coincident with the measured voltage dropping down to 1V (or less)?

Where was the ground reference probe (black lead) of the meter placed when you were making these measurements? On the block or at the battery post?

With the probes placed in the location where you saw the voltage fluctuations try wiggling the wires/harness to try and simulate the vibrations experienced when the engine is running?

Cheers, Mark

First, you cannot use a volt meter to check the high voltage side...just like Corvette64 said.

Second, remove your cap and rotor. Look at the rotor closely on both sides near the center. HEI rotors typically fail by arcing thru the plastic near the center and allow a ground to the distributor shaft. The symptom begins as a random miss and eventually grounds the thing entirely. If it is a white rotor, the arc hole is easy to spot, on a black rotor, it is tougher to see.

mike in tucson