The motor is probably vapor locking. Gas boiling. Under hood temps to high. Crappy gas. Does it have a electric fuel pump? Removeable hood sides. Insulate the fuel lines. Move them away from the exhaust. Make heat sheilds. Ceramic coated headers. Header wrap. Spacer under the carb. Just how hot is the motor getting? Does the shroud have baffels that open at speed to let the air thru the radiator? What temp does the fan come on?