HEI Ignition Control Module Grounding Alert Accel 59107

methylgroup

I have a 1981 El Camino with a '74 sbc 400. It has the Crane Blue Racer hydraulic cam, Crane roller rockers, Edelbrock 650 cfm carb, Super T10 4 speed, and the Accel 59107 HEI, vac advance, coil in cap, with the ignition control module. I installed the distributor four years ago when I built the motor, and it ran fine until 4 months ago, when the motor would just cut off driving down the highway at 70 or so. I keep a spare ignition control module in the glove box, and after changing it, the motor starts right up and runs fine. This happened four times in 4 months. I spent time on this site and on the Web, and I found out the following information.

My problems are directly due to poor grounds both in the distributor and the car in general. Be sure to clean all your grounds at least once a year, and every time you change the battery. The battery posts should of course be clean, but also sand the fusible link from the battery ground to the body, the ground strap from the motor to the fire wall, the two headlight ground wires above the headlights on the interior of the radiator support bracket, the rear tail light and fuel sender unit ground on the underneath of the rear bumper frame, and the interior ground above the emergency brake mechanism under the dash.

The real cure for my problem was to run a new ground wire from the capacitor grounding screw on the inside of the distributor, out of the distributor to the firewall side of the engine ground strap. It seems that the stock internal ground through the body of the distributor to the ignition control module has high resistance, which causes the module to overheat and shut off. Running a separate ground wire to the firewall improves the grounding circuit enought to make the module not only work better, but run cooler to boot. I highly recommend that every El C owner run such a distributor ground wire at their earliest opportunity. Drive it like you stole it, Robert

methylgroup

I have continued to work on the ignition control module question. I have found several more things out. One is, the ignition control module has an internal thermal switch, which shuts off power to the module if it overheats. If you open the hood and wait 20 minutes for the motor to cool, it should restart. However, if the ground is bad, you can expect it to fail again, as it did for me 4 times before I fixed it. Since my last post, I have run a #10 wire from the firewall ground strap back to the fusible link ground at the battery.

Another thing I've learned is about the amp draw of the coil. The HEI coil draws about 1 amp per 1000 rpm of engine speed, and the stock ICM has a maximum amp rating of 5 amps. As engine speed increases, the time available for proper coil saturation decreases, while the amp draw increases. Bottom line: the stock coil and ICM are adequate for engine speeds of less than 5000 rpm. In my case, the cam I have makes max torque at 2000 rpm, and max hp at 3200 rpm, so spinning it past 4000 makes no sense. Likewise, buying a high output (7.5 amp ) ICM and high output coil makes no sense unless you have a high rpm screamer, in which case you need the additional ampacity. Robert