Last year I rebuilt my military 302 with cast iron headers and a Clifford intake manifold mounted with a Holley 390cfm 4-barrel carb. At higher revs, 2000-3000, it pours out power, but running through the gears there is an ultra-annoying dead spot just following each shift at around 1500. Is this overcarburetion? Something I can solve by rejetting? Or do I need more carb heat or intake preheat?
This manifold is heated by engine coolant passing through a jacket in it.
The engine is in a '54 GMC 350 2-ton, and does a lot of hauling.
