hughesboysvaliant said

Hey, had the same problem. Its your accelerator pump squirter, you don't have enough fuel to handle the hand off of from the jets to the power valve. when you go wot the transfer circuit takes time to hand off the duties form just jets to jets and power valve this is the duty of the accelerator pump and squirter. I had to go up to a 40 on my 750 to get rid of the hesitation and move my screw on the pump cam to the second hole. The spacer gives more plenum volume that has to be filled with fuel air mix this also will require more accelerator pump shot. The problem is a lean condition at wot due to insufficient pump shot.

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pntastar69 said

I'm still tryin to dial in the 670 as well. Went from a .031", to a .032", then to a .035" squirter. It helped some but still a slight hesitation off idle. Running a 4 speed as well. I even played w/the initial timing a bit, now up to 16 degrees from 12. Drawing 15 inches and the power valve (6.5) is working. Using ported vac. adv. too. Ordered the holley pump cam kit and time to experiment w/them. Looked at the profile and chose the black one for a trial. Readjusted the acc pump and worked pretty good. Ran the car to a cruise yesterday, 1.5 hour run each way. Still have a slight hesitation but its better than before. Gonna experiment w/different cam profiles and hope one corrects it. Once I get passed the hesitation off idle, no other issues are present. Worked like a charm cruising and WOT.

Don't mean to steal your thunder but seems (we, and most) have similar issues w/this carb. The pump shot arm is also resting on the pump cam, not on the wound spring, like some 670's were.

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