Backfiring out one side.. Need some help..

[CobraCooter]

I had the same issue.. it was a hair line crack in the spark plug insulator

[LG57]

When I had this issue, it was internal corrosion in the distributor cap.

[blown871]

.. take potato out of other side...

[MOTORHEAD]

Use process of elimination; Put the pass side plugs on drivers side, and vicea versa. If problem switches to drivers side, it's a bad plug. If it stays on pass side it's not plugs.
Replace the dist cap next, some electrical defects cannot be seen.
Replace ign wires on pass side.
Still no joy?
Pull pass side header and look for signs of leakage. A leak will leave a soot trail, or other gasket damage may be obvious.
still have problem, try a new coil.
Belay all the above, you have a backfire, not a miss.
Could be induction or exhaust leak.
Are you sure it's not a miss ?

[MOTORHEAD]

Use process of elimination; Put the pass side plugs on drivers side, and vicea versa. If problem switches to drivers side, it's a bad plug. If it stays on pass side it's not plugs.
Replace the dist cap next, some electrical defects cannot be seen.
Replace ign wires on pass side.
Still no joy?
Pull pass side header and look for signs of leakage. A leak will leave a soot trail, or other gasket damage may be obvious.
still have problem, try a new coil.
Belay all the above, you have a backfire, not a miss.
Could be induction or exhaust leak.
Are you sure it's not a miss ?
backfire under load, has to be cross-fireing, dist cap, or ign wire. Wire doesn't have to be bad, might be another lead inducting current into ajacent wire.
427's have this problem on #7&8 cyl. If you think it's #1 cyl, try isolating wire from others.
Thinking out loud here.

Ted

[40k Later]

I hope you didn't have the same problem I just found. Backfiring exactly as you mention but only the left side. Tried plug swapping, pulled one wire at a time and put a plug in it and each fired so wires were good. Never backfired before so I knew no carb issue. Looked at Dist cap and rotor all looked good and again each plug wire fired. Took off my valve covers and cranked the engine with the coil wire off and viola!! Rocker arm barely moving. Flat lobe on my hydraulic flat tappet cam.