One of the drawbacks to mechanically linked slides is a lack of positive response to large and sudden changes to throttle position.
When the throttle is near idle position and the engine is turning, the intake strokes of the pistons lower atmospheric pressure in the carb throats. The differential pressure on either side of the jet orifices causes fuel to flow through the jets into the carb bore. The amount of suction produced is relative to RPM of the engine. When slides are suddenly open at lower engine RPM, the pressure differential across the jet orifices equalizes resulting in less flow and less fuel to provide engine power. To aleviate this, these carbs are run very rich, so the leaning effect of open the slides is somewhat ameliorated. However, this can only compensate just so much. The 77 and 78 carbs generally ran leaner at idle than previous models. They were fitted with accelerator pumps to provide the extra fuel needed when the slides were suddenly open. Most models switched to CV carbs to eliminate the lack of proper operation of the throttle required for the earlier carbs and still maintain anti-polutive carb settings. CV carbs control slide opening based on engine vacuum.
Unless you run the early carbs way rich on the low throttle settings, it is unreasonable to expect engine response from a suddenly snapped open throttle. However, throttle position changes of 1/3 or 1/2 full overall throttle travel should provide spirited engine response. This can be helped by larger slow jets, a rich pilot screw setting. Or, if the hesitation persits in mid throttle to full throttle settings, raising the needles, or selecting a steeper taper profile of the needles. Air jet size and emulsion tube hole sizes and placement can also tuned for mixture, and thus, throttle response.
Cheers,
