I have a 85 grand wag. new carb, new fuel pump, new plugs,wires, coil ,ignition modual,distributer.the tank runs great up to 55mph but when pedal is to the floor the engine stalls but at half pedal she runs untill 75mph the dose the same. Any body have a clue?
Could be possibly three items combined that are causing trouble.
Spark advance could be the problem, check it out with a timing light through various RPM's....look for a flutter in the mark under quick throttle movements, also under mid rpm ranges 2,500 - 3000
Second item to check is loss of vacuum. If your timing is using vacuum this could be the problem...Also check all vacuum lines to the carb.
Third item is carb running dry...low bowl level...
low bowl level would act a lot like the problems you mentioned. [img]images/graemlins/40BEER.gif[/img]