tryin to break in new engine, ruff idle

Its either timing or the cam is already wiped out. I mean for flames to come out of the carb.

A bad plug wire should not cause it, unless you got 2 bad wires and the spark is jumping across the wires.

Don't think too rich or lean from the carb would cause flames either.

What is your timing set at, like total timing? Have you turned the dist while the motor was running and listen to the engine rpms increase and decrease as you advance and retard the timing?

I like advancing the dist--with vacuum advance disconnect--and hearing the rpm's pick up, once it seems to not be increasing in rpm's stop advancing the timing and back it off a touch. That should give it around 35 degrees total timing.

If the timing is right on 35 give or take a few and the motor is still acting up, I would run a compression test on all 8 cylinders. They all should be close to the same psi, if not pop the valve cover off and see if the rockers are moving the same distance down opening.

You did tighten the rocker shafts correct, I had rocker shaft bolts snap but that was at high rpm's. The shaft will bend if the end bolts break--still I had no flames, just miss