45mph

my 1946 chev has been converted to a rat rod somewhat. i had to start from wire 1 as the wires were cut at the firewall.it is now a 12v. this car has never gone over 45 mph. if you are doing 40 on down, it runs ok. when you get to 43-45 it starts to spit and sputter and at that point your foot is to the floor. i need HELP on this one. the carb has been rebuilt and the timming is good.

It sounds like the carburetor may still need adjusted a little.