I second the choke check.

He said he swapped the carbs and it did the same thing so not choke or acc pump. Shot in the dark but the ign module is grounded to the block in the rear with main ground. Take nut off and clean all corrosion off the stud and washers and re install.

Chris

Choke heater wire getting 12 volts.

Was it timed in base timing mode? I believe you have to do that with the TB-V.

Two odd things I ran into sepetately.

Years ago had to grab a Thunderbolt IV cap from Napa on a Sunday The posts where numbered wrong. Uggh.

Also, have had 2 engines (454 and 502) with broken valve springs that still held the valves so compression okay and idle speed okay, but start to give throttle and pop, pop.

I haven’t run into, but could swear I have read over the past 100 years on OSO and others, the bolt pick up assembly or module causing weird issues like this for a few people.

The choke is mechanical off the choke stove spring. I verified the choke was open fully. This distributor does not have a base timing feature. From what I have read, because there is no knock sensor to provide feedback it is just a electronic advance. All 4 caps (new and old) are numbered the same. I put the old cap and wires from the port engine on the motor in question and had the same backfire.

any ticking sound at idle, collapsed lifter, intake valve way out of adjustment, time to pull a valve cover

Choke +12 volt would not follow carb, he is in MI and it most likely is cold up there. Backfire through carb usually indication lean carb or ignition.

Which timing module you have? Is it the 1" brick older style or the triangle, if the triangle it will have a number on it.
I also have heard that the timing pickup block inside the distributor will cause some weird problems.

Strong compression was mentioned earlier. I’m thinking something is up with the distributor.

Also, the manual states that the module has to be in base timing mode to set. It made no mention of a difference between having the knock module or not.