OK, small 260 with a Ford 4V intake, Comp Cams Hyd. cam 212/212, automatic and stock exhaust.
Here's the problem. When starting off, as from a stop sign, rather slowly, the engine takes the gas then hesitates.
Not an accelerator pump hesitation as this happens after the pump has shot it's gas. After checking a few things, I started it up, put it in drive, then slowly increased the rpm. At around 850/900 rpm the engine begins to run rough due to what I think is a lean condition. I then hooked up a vacuum gauge and did the same test. Same result, 850/900 rpm rough - 12 ins. vacuum. As I increased the rpm the roughness [lean] condition remained until the vacuum reached about 8.5 ins. and then the roughness went away. This was noticeable as if the power valve had opened.
I've played with the timing - no change, double checked the carb and transition circuits for cleanliness, tried slightly larger jets and no change. My thought now is to go with a Holley 10.5 ins. power valve, as I have tried everything I can think of. I don't want to cover up something with the Holley power valve, so any ideas would be appreciated.
Rob
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HAVE A NICE DAY!!!!