47 V8 ignition mystery

[Terry,OH]

Watching the flashes from a timing light at idle, (either in line or clamp on type) can indicate which cylinder has a firing problems. Look for missing flashes using a good cylinder as reference. If all the cylinders appear the same, what was your vacuum reading at idle? Should be very close to 20 maybe slightly lower like 18 and very steady. While you have the vacuum gauge attached adjust carburetor idle mixture screws, while enging is warm,g for the highest and steadiest vacuum reading and engine running smoothest. The screws should be about 3/4 to 1 turn out from full close. Small adjustments should make a big difference. If the adjustment can not be gotten or out of adjustment range or screws don't make a difference the problem would appear to be in the Carb. Hard to believe the engine running rough and the vacuum gauge not reacting at idle. While driving the gauge should be moving low and high with acceleration and deceleration IMO Your postings don't seem to give enough information on what your doing or seeing.