HOT 440

HI I OWN A SECOND HAND VOLVO 440 WITH I THINK THE SAME ENGINE AS THE RENAULT 21 SOLEX CARBU AND ALL THE CAR HAS 125000KMS UP AND RUNS VERY WELL BUT THE ENGINE CUT OUT WHEN THE WEATHER IS HOT NOT UNUSUAL FOR THE SOUTH OF FRANCE ALL THE ELECTRICS HAVE BEEN CHANGED PLUGS HT WIRES DISTRIB CAM AND CAP AND THE RENIX HT UNIT SAME PROBLEM
THE NEW FUEL PUMP AND PIPES HAVE MADE NO DIFFERENCE
A COMPLETE REBUILD OF THE SOLEX CARBU HAS NOT HELPED EXCEPT THAN WHEN THE OUTSIDE AIR TEMP IS OVER 25C THE PIPE WHICH RUNS EXTRA PETROL BACK TO THE FUEL TANK IS FULL OF FROTH AIR OR FUEL????
HELP. THIS IS A GREAT CAR I DONT WANT TO CHANGE.