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

  1. #1
    Join Date
    May 2015

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

    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?

  2. #2
    Join Date
    Dec 2011
    New Haven, Ct


    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
    GM World Class Certified Service Technician.
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