Have a '52 w/new carb and starter runs fine until I drive facing uphill. Surging then stalls, quickly , adjusted floats [twice], full tank of fuel, line clear, runs fine every way but forward up hill ,run backwards, sideways, but point it up ,it's out. 241A Marvel S. Presently rebuilding old original. Removed new carb. 2 times, cannot see where stoppage is occurring. Thanks.