Grounding minus coil termial for no start?

[ZEKE68]

Is it safe for the HEI ignition module to ground the minus terminal to prevent an engine start? Would this prevent a start? Someone threw it out the other day in the thread about a hidden switch to prevent starting. I guess that would be the tach terminal on the HEI.

[clay68c10]

It would probably work, but may hurt either the coil or module. I would just switch the positive side.

[TruDom]

why wouldn't you just put the switch in the 12v ignition wire? open switch = no power for ignition coil.

[LH Lead-Foot]

It will work without damage to ignition module, but is not common practice. Controlling B+ to the HEI is best practices. Note; If you measure the current to the HEI coil, you will find it is pretty high as the coils primary is 1.2 ohms. Use a toggle switch and a relay to handle that current. Note the resistance of high voltage coils sold by speed shops. The lower the resistance, the higher the current, but higher the output voltage.

MATH; 14 volt DC divided by 1.2 ohms = 11.6 amps. (E over I X R) Ohms solving circle.

Old trick, Anti-Theft using starter;
If equipped with cruise control, the set switch goes to ground on many GM vehicle produced before 1986. Fused B+ to relay to handle 20 amps or more, can be energized by "Set" button on coil side of relay. Ignition switch purple wire goes to started for crank, so interrupted by relay contacts.

Operation; Key in right hand, while left hand finger on set button and held on during cranking, will complete circuit to starter's solenoid. Turn key to crank normally, release cruise set switch, cruise operates normally while driving.

Important; check your cruise control's set switch for normal operation with key on and some and newer vehicle provide B+ signal instead.

[ZEKE68]

I am not that smart, but if I wanted to steal a vehicle that had a distributor, and I had no key, and I could open the hood, I would just run a wire from the battery positive to the coil positive, and jumper the starter with a screw driver. I just thought that if someone like me tried that and it didn't start because the negative was grounded that it may confuse them enough to give up. A wire from the battery would bypass all of that positive side stuff.

[kwmech]

I've done it since 1976 in a van I bought brand new. NO problems ever from grounding an HEI

[clay68c10]

Originally Posted by kwmech

I've done it since 1976 in a van I bought brand new. NO problems ever from grounding an HEI

Good to know!

[TruDom]

Originally Posted by ZEKE68

I am not that smart, but if I wanted to steal a vehicle that had a distributor, and I had no key, and I could open the hood, I would just run a wire from the battery positive to the coil positive, and jumper the starter with a screw driver. I just thought that if someone like me tried that and it didn't start because the negative was grounded that it may confuse them enough to give up. A wire from the battery would bypass all of that positive side stuff.

makes sense then. let us know how it works out.