when i push the gas pedal down about 3/4 with the air on, the car nose dives before the car shifts into the next gear. it might be a fuel problem, but i've replaced the fuel pump and filter twice. am i missing something? is there a filter in the tank? anything else it could be? thanks for the help. oh yeah, i have a 305 HO with a carb.

 

What is the shift point (engine RPM) at 3/4 throttle? The induction/exhaust systems may be "maxxed-out" before you shift, or the valve train may be into an RPM range that allows the valves to float off the seats.