Feeling of Power Surging/Loss While in Motion at Steady RPM

[Jasper]

My 1970 power train was completely overhauled about 400 miles ago. The car ran fine at first, but has since developed some power delivery problems. I first noticed the engine running rough and then a lot rougher. It back fired explosively twice and I felt lucky to get it home. Since then, the back firing has stopped and the engine seems to run a little better, but progress is not smooth when I drive at a steady speed. It feels like the car is surging slightly on a fairly regular basis i.e. every few seconds. The car's speed and the motor's revolutions do not change on the instruments, but I can feel a continuing series of small losses of speed followed by immediate recovery. My first thought was that I was experiencing a misfire, so I checked every plug wire with my timing light and found no indication of misfire. The car has transistorized ignition and the carburetor was professionally rebuilt when I had the drive train done. Where should I start looking to locate my problem?

[c4c5specialist]

Hi there,

Place a vacuum gauge on the engine and see if you have a steady needle. This meaning about 17-19 inches of vacuum but the needle should not fluctuate.

Let us know what you have.

If it does not fluctuate, I would remove the spark plugs and check for any being darker in deposits than the rest, could be a drip from the carb causing a rich misfire.

Carb fasteners can loosen with time, so its a possibility.

Allthebest and please keep us posted. Paul