I have a performer 600 on top of my mild build 350. I have 5 psi going to the carb through an electric fuel pump. From a dead stop when I stab it there is no hesitation, but if I gradually give it gas once I hit the mechanical secondaries there is a flat spot or slight hesitation then its ok. I havent messed with any of the jets or metering rods, or even the floats for that matter. Any suggestions?
Could be the springs for the metereing rods are too light. There is a booklet that comes with the Edelbrock carbs, if you don't have that book, it's downloadable from the Edelbrock Website, for free. It's the best troubleshooting tool for those carbs, it includes the calibrations of various carbs, and part numbers for various kits.
as already said.....get a calibration kit and follow the instructions in the the manual is it a 1405 or 1406?
If it's the type with the secondary air door, you may need to delay the opening slightly. I believe there is a spring adjustment. When you stomp on it, you are still running off the pump shot when the secondaries open. You won't have as much extra fuel in there rolling into it.
Its also a good idea to drive the car with a vacuum gauge inside where you can see it. Make it run right, then drive it like in normal traffic, and record the lowest vacuum on accelerating. Put in springs that are one inch lower than the recorded vacuum. This will give great fuel mileage, and the best performance. Check the vacuum advance in the distributor, if its sticky, it can cause your problem.
Timing!!! Check timing and at what rpm advance is all in at. Check what rpm the stumble happens maybe a timing issue and not the Carb at all
that description sounds like an accelelorator pump issue. too much or not enough fuel to carry you across the transition to the secondary opening point...
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