HEI voltage question

[xirxious]

Does the input wire have a minimum volatge requirement to operate? It checks out fine, but I'm wondering if when the starter ingages, if its dropping the voltage alot? I think the bigger problem is in the carb with no or bad gas, but I thought it should at least thump a couple times even with splashing a little down the carb. I put a timing light on the plug wires, found the ones not sparking and put new wires & plug on it. The distributor/cap/HEI coil is new as well.

[Co-Dog]

If the engine is cranking over pretty good then you should have enough voltage to fire the ignition. That is assuming you don't have other wiring issues causing resistance in the ignition circuit. You should check voltage at the coil while cranking the engine. If you've got at least 6v it should fire, but you shouldn't see less than 9v.

Is this an aftermarket distributor, you may not have a wide enough gap at the plugs.

[philofab]

An HEI should have a 10 guage wire run to it. If it's hooked to stock wiring it may not be getting a full 12 volts. Many cars had ballast resistors or resistor wire running to the stock coil. A GM HEI should run on as low as 9 volts but 12-14.5 is required for good performance.

[JONES PERFORMANCE]

you may need a new coil. hei coils will get weak and not produce enough voltage. i have replaced coils with new ones from pep boys and tested the output of the secondary on a scope and it was worse than the coil i replaced. best place to get a replacement coil for an hei is from the boneyard, the gm coils are the best other than some of the aftermarket ones.

[philofab]

I've never had a problem with a HEI coil unless the ground strap is missing. Then the coil will overhead and destroy itself in short order. However I have had a lot of ignition modules go out in HEIs.