Car Stumbles When You Accelerate

Discussion in 'Holley' started by mltdwn12, Mar 19, 2008.

  1. mltdwn12

    mltdwn12 Founders Club Member

    I leave from a stop, part throttle, shifting manually. Get to about 2500 rpm car seems to stumble or surge, shifting doesn't change it. If I really step on it as the secondaries are tipped in, it flattens out. Carb is an 850 DP. Fuel pump is a RobbMC mecahnical pump that is built for about 13 pounds and a new Holley dead head regulator and no return line. Motor was set up on the dyno and made good power with the set up. Only difference is the fuel pump was a RobbMC pump that was putting out about 5 pounds of pressure on the gauge.

    I'm thinking it's a fuel issue. At idle I can't get the fuel pressure down below 8 pounds. Turning the regulator screw has no effect. I had a fuel pressure gauge on the fuel line. Put a bigger Autometer pressure gauge and saw the same thing at idle. Haven't taken it out on the street again with the gauge temporarily mounted at the base of the windshield so I can see what the pressure is when the r's go up.

    Anyone else had this kind of issue? You think it may be too much fuel pressure? Does the fuel pressure increase with rpm?
     
  2. 70aqua_custom

    70aqua_custom Well-Known Member

    not sure what you mean by "flattens out" but it sure sounds like you have a bad regulator there. I'd change the regulator and adjust it then check the pressure at all operating RPMs. You're looking for 4-7 psi. You can do this with the engine running in neutral.
     

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