mad box 6al

[95rayburn]

Would a bad msd box cause the motor to miss and quit? Free revs good but when u put motor under a load missing and quitting

[RCJ]

When a motor runs fine under lite loads, but misses under heavy load. I start with the ignition system.

[LIS20]

Check the wires at the connection between the distributor and msd box -
green goes to purple not green to green

[turtle1hp]

Check and clean all connections. I changed every part in the ignition system, including the power switch. No luck.... I had corrosion at the battery ground cable to frame connection. Even though the bolt was tight, over time, washing the car and such, corrosion built up just enough to cause the exact same problem. I was surprised that was the problem because the starter would still spin the motor like normal.

[RCJ]

I clean the motor mounts and frame pads everytime I change motors.A friend of mine had HEIs keep going out,A bad ground at the at the motor mount was the problem.I have heard of people running ground wires from the heads to the frame, that would prevent some problems.

[rakracing]

guy I run miss 3 weeks with very similar issue, car ran great in garage get to track and under load would miss bad and not run, after 3 weeks they rented the track and found when they changed motors they tugged on the wires to the coil and the wire was stretched with only 2 strands making connection , like what was said check grounds, and connection and even pull on wires,

[95rayburn]

Put a msd hei distributor in it cuz didn't have a msd box. Took to track still missing. So put fuel pump on cleaned fuel filter lift bottom Hose off fuel line. Car ran great for the feature