Backfire when warm ??

[HOTROD]

This we been working on for a wile know ---When the car warms up it starts backfiring !!??
This is what we did Replaced Cam & lifters (rounded off lobes) spark plugs, wires,coil,and changed the carb (three different ones) and I used all extra Elect. parts I had (now i no they all work) each time started runs good -warmen up and dam backfire !!
the distributor just was replaced with a new one last month He drove the car around and backfired   Any help Thanks Guys.
1970 RR 383 only one thing the engine bay looks stock and then I looked under the dash---and It looks like a race car set up!(The wiring under the dash)

[bobs66440]

Is it backfiring through the carb or exhaust?

[resq302]

Almost sounds like a mixture issue since it does not do it when it is cold (probably with the choke on) it is richer.  Could also be too that you have a vacuum leak that when the engine warms up, a part expands causing a bigger gap sucking more air in causing a lean condition.

[HOTROD]

Exhaust .
I am thinken a Hole some were ? (vac)

[bobs66440]

It sounds like the coil is going bad, but you said it's new...do you have another you can try? ...and you are running a ballast resistor, correct?

Check for vacuum leaks.

What is the timing set at?

Also, double check your firing order...make sure the plug wires are run correctly. Believe it or not, this is a common cause of tuning issues.  

[HOTROD]

We are going to check the Intake for holes and going to get a pic of the wiring .
The Ballast Resistor is Question able along with the wiring .
But got to what tell my Friend gets back from Cal.