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Surging problem at higher engine speeds with R1, Edlebrock

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  • Fuel System: Surging problem at higher engine speeds with R1, Edlebrock

    I've had an Edlebrock 1403 on my '63 GT with R1 for almost 8 years, been quite happy with it. But recently it started surging badly every time the engine speed gets relatively high -- either over 60 MPH on flat ground, or over 40 on a hill climb. The engine surges so badly that I have to pull over and shut it off briefly to get it calmed down. (It always starts right up again.) If I don't shut it down right away it will start back firing through the carb and then quit on its own. The car runs perfectly fine at lower speeds and will accelerate at full throttle briefly.

    The only adjustments that have been made the last few weeks were some minor carb adjustments to lean out the idle mix a bit and lower the idle speed a bit to try to reduce dieseling (which was fairly successful). I have an electric fuel pump at the tank pumping through the stock fuel pump, with stock fuel line and return line. (The electric pump is primarily to prevent vapor lock, also improves starting after sitting for a week of course. Having it on or off doesn't seem to make much difference when driving in cool weather.) I use premium fuel, though the compression ratio was reduced some by using thick head gaskets when a valve job was done. I had a "smoke test" done by a local garage to try to find any possible vacuum leaks to no avail.

    Anyone seen this condition, and what did you do to correct it? A friend has suggested throttle body fuel injection, but I'd rather not stray that far from originality.
    Gene Nagle
    1963 Hawk R1
    1985 Avanti

  • #2
    Check your float level, sounds like either it's too low or your fuel pump is going bad and not supplying enough fuel. My info says the original R1 AFB carb was 625cfm, why did you change it to a 500 cfm replacement?


    • #3
      It sounds like it could possibly be a clogged fuel filter and
      starving for gas.
      Last edited by paul shuffleburg; 03-12-2019, 11:29 AM.


      • #4
        Possibly the pickup sock in the tank is clogging with debris(mud/rust) after a little running. Also try a fresh fuel filter as the same could apply to it as well. Recheck the float level to ascertain nothing has changed. Check the bowl for same debris. As Paul stated, it's starving and you just have to find out why.


        • #5
          MANY THANKS to the 3 guys who have taken the time to respond. I will change the inline fuel filter that I put in ahead of the electric pump and get a hold of a repair kit for the Edlebrock so that I can take it apart.
          Gene Nagle
          1963 Hawk R1
          1985 Avanti


          • #6
            Ben -

            Because cfm wise, the 500 version will carburete better than the larger 625. Throttle response will be a lot more crisp, mileage should be a tad better.

            Hawk -

            FIRST...remove the mechanical pump. It's redundant, not needed and potentially dangerous. It can dump fuel into the oil pan with the smallest diaphragm leak...
            Depending on your pump, it sounds like it might not be putting out enough VOLUME, or...enough PRESSURE to pump past the mechanical pump. Another possibility, the floats may be adjusted too low, but this sounds least likely.
            BUT, by your basic description of running well, to cutting out, to shutting it off, to running again, look at the pump. lines, and filter(s).
            The possibility of a fuel line blockage. Either at the initial opening in the tank or along the length of the line. Possibly a kink somewhere.
            And yes, as has been mentioned filter(s).



            • #7
              Download this.
              Go to page 23.

              HTIH (Hope The Info Helps)


              Get your facts first, and then you can distort them as much as you please. Mark Twain

              Note: SDC# 070190 (and earlier...)


              • #8
                I would Tee in a fuel pressure gauge just before the carb to make sure the pressure is OK when the surging starts.
                At least this will let you know if it's the carb or before the carb.
                A pickup sock was mentioned, but my 1950 jus has an open tube to pick up the gas in the tank.
                What years of Studebakers had pickup socks in the tank?


                • #9
                  Make sure this is not an ignition problem. Numerous breakerless conversion kits and newer aftermarket coils break down electronically. I would question the ignition especially because it backfires.
                  james r pepper


                  • #10
                    Had a bad (leaking) coil cause such symptoms on a 64 Criuser once.


                    • #11
                      A tach or Dwell meter will jump around or shut off if Ignition is breaking up. Easy to analize when driving. That and a vaccum guage show a lot of scratching you head.