2 quad spark box failures?

[ntstlgl1970]

I had one of the quad spark boxes fail on my gen3 hemi (one output shorted to ground) after 150ish miles on a new engine. Checked the coil primary resistance (1.2-1.3 ohms) against 3 other coils, measured ok. Verified the output from the Ms3x was not driving the quad spark on for that cylinder (8). Replaced the quad spark with a new one, car runs great, but after 30 minutes of running, car drops a cylinder. New quad spark failed, this time output shorted to ground for cylinder 2 (same bank). I'm thinking I have the dwell set wrong maybe or is there a temperature limit on the quad spark? I have them mounted to the back of the cylinder heads, but spaced off the head about 1/8" to 1/4". I will attach my msq.

Nominal dwell @ 3ms
Spark duration @ 1ms
Standard dwell
Wasted spark
Spark output going high

Any ideas?

Thanks
Eric

[slow_hemi6]

They thermally shutdown around 185C.

[ntstlgl1970]

I'm wondering if the 3ms dwell and waste spark is too much when combined

[jamies]

check leads and spark plugs, any additional resistance here increases the flyback load on the IGBT which can contribute to it failing

[billr]

Check the power grounds to the Quad Spark, too. I know little about those units, but am always suspicious of grounding when a problem "moves around" like this.

[ntstlgl1970]

I put new plugs in recently, this is a coil on plug setup. The grounds "should" be good, but I will measure the voltage drop at each of the grounds. They are terminated at the head on each bank.
Thanks!