Maybe some more history, how long have you owned the car? Has this been a problem since you've owned it or did it suddenly develop last fall?
Well you replaced the plugs, plug wires and coil. What about the distributor cap and rotor? Sometimes the cap will develop a carbon track and the juice will follow the track resulting in a miss fire.
Try putting the timing light on the other plug wires to check if they are firing intermittently as well. If all the plugs are firing correctly except number one I would suspect the plug, wire or cap/rotor. If they are all firing intermittently I would suspect the plugs, wires, rotor/cap and module. Although I've found the module either works or doesn't. But if you have replaced the plugs, wires and coil you can concentrate on the cap and rotor or the wiring to the distributor.
Is the distributor an HEI? If so it will require 12-14.5 volts to operate correctly. If originality is not and issue I suggest installing a relay/solenoid to power the distributor. Use the ignition switched wire to turn the solenoid off and on and power the distributor through the solenoid from the battery or the alternator.
If the car has to look original you may have to replace the wire powering the distributor from the ignition switch. Originally they were a resistor wire and only supplied the points distributor with about nine volts after it started.
The condition of the wires and connections may be the fault as well. Any corrosion at a connection will result in a voltage drop across the connection/splice. If the wiring to the distributor has some crimped butt splices, that could be the source of the voltage drop. Better to crimp, solder then heat shrink the joints.
Found some time to investigate, do some work.
Bought the car in Apr 2016 for our 40th wedding anniversary. Not totally done, but (almost) turn key. Pontiac 350, edelbrock carb, 4 speed. Needs rockers but we like it. Been working thru the issues as we find them.
Resolved overheating issue thanks to this site.
It's always idled rough. According to the paperwork I was given, it has a Comp Cams part # 51-116-3, lift = 516/516. I thought the idle was normal, cam related. It has good power once it gets moving. Heavy gas smell out the exhaust. Maybe 7mpg. I get better mpg w/my 70 GMC big block.
I figured it needed a tune up, check plugs to see if its running rich. All plugs looked great. #1 & #3 plug wires had rust inside the boot. R&R plugs and wires, gap = 045 for pertronix HEI. Went to time it, noticed the intermittent spark.
I read your reply, last part about the wiring. I found lots of crimped connections, a guillotine crimp in the distributor power wire. I pulled the distributor to solder additional 16ga wire and a ring connector. R&R'ed crimp connections for electric choke on the carb, connection for in hood tach. I firmly believe the guillotine connector for the distributor is (was?) my problem. It looked like not many strands were left.
Put it all back together. All she wants to do is back fire out the carb. Im thinking timing but I do not recall which way to turn. I work alone, 911 is a 10 minute wait, carb fires bother me. Had a bad one long time ago. Aint that young anymore(smile).
