I have a 1973 124. When the car is running, either cold or at full temp, the car will begin to buck. The pattern is rhythmic, 1 about once per second. Gradually worsens in intensity and the car slows. If I tried to power through it, it gets worse. Up shifting makes it worse. Letting off the throttle eases it a bit, but it doesn't go away. When I put it in neutral and coast a bit, the bucking ceases. When at rest, in neutral, and I throttle up, the engine sounds good for 15-30 seconds then develops a subtle "stumble".
I had the top end freshened up this fall. Ran great after that. Also upgraded to Pertronix Ignitor electronic ignition. Headlight relay system installed.
Reading through the messages, the symptom seemed like either a fuel filter or gas pump. I replaced each one, separately, so I might know which worked. Nope, neither one
Pulled the plugs: the first one had clean oil in the well. the first three plugs had some black shoot around the outside, tan/wire near the electrode. I got too frustrated to get the 4th one out 
. The oil is fairly clean, but smells alot like exhaust. I tired some Sea Foam, both through the carb and then in the tank. No real difference.So, I am hopeful someone can use their clairvoyant powers and give a diagnosis!
Jim
