That is a progressive 2 barrel carb. Make sure the secondary is opening. If the choke does not open all the way the sec. won't open. Make sure the accel. pump is working good. You may need a larger main jet. I've never used one on an old truck or car but the Pinto's & Mustang 4 cyl. engines used them & they were hard to get right then, but that was mostly from the auto trans. & A/C. They didn't have enough power to run the car & A/C at the same time.
