REBUILDING THE 4 LITRE ENGINE
THIS IS THE STORY OF THE REFURBISHMENT OF BERT DEGENAAR`S 4 LITRE BLOWER ENGINE. BERT HAS KINDLY SUPPLIED THE PHOTOS TAKEN DURING THIS WORK THAT WAS CARRIED OUT BY A LOCAL ENGINE RESTORATION COMPANY NEAR AMSTERDAM IN HOLLAND.
ABOVE, A VIEW OF THE RIGHT HAND SIDE OF THE FINISHED ENGINE. NO EXPENSE WAS SPARED IN THIS RESTORATION AND IT CAN BE SAID THAT IT WAS A TRULY INTERNATIONAL PROJECT, AS THE PISTONS AND CON RODS WERE SOURCED FROM ARGENTINA, THE NEW IN HOUSE DESIGNED CAMSHAFT FROM THE UK AND OTHER PARTS FROM VARIOUS COUNTRIES. THE ENGINE HAS BEEN PAINTED AS THE CRANKCASE ASSEMBLY AND SUMP ARE MADE FROM ELECTRON AND PRONE TO CORROSION. I HAVE VISITED THIS WORKSHOP AND THEY ARE WELL EQUIPED WITH EXOTIC ENGINE RECONDITIONING MACHINERY.
ABOVE, THE MASSIVE CRANKSHAFT,, FLYWHEEL AND CLUTCH ASSEMBLY BEING BALANCED AFTER THE CRANKSHAFT WAS RE-NITRIDED AND THE JOURNALS RE-GROUND. NOTE THE MODERN CLUTCH ASSEMBLY.
ABOVE, THE CRANKSHAFT ASSEMBLED INTO THE CRANKCASE. THE DESIGN OF THE 4 LITRE CRANKCASE WAS RADICALLY DIFFERENT TO THE OTHER BENTLEY BENTLEY ENGINES WHICH WERE ALL BASED ON THE ORIGINAL 3 LITRE DESIGN OF 1919. THERE ARE TWO WAYS TO CONFIGURE A CRANKCASE, THE EASIEST WAY IS TO HAVE THE SPLIT BETWEEN THE CRANKCASE AND SUMP ON THE CENTRELINE OF THE CRANKSHAFT THAT THE ORIGINAL 3 LITRE ENGINE DESIGN ADOPTED. THIS MEANS THAT THE SUMP HAS TO CONTRIBUTE TO THE STRUCTURAL INTEGRITY OF THE CRANKCASE.
THE OTHER WAY IS TO HAVE THE CRANKCASE AS A SINGLE STRUCTURAL COMPONENT AND THE SUMP MERELY AS A CLOSING PLATE. THIS IS THE WAY THE 4 LITRE CRANKCASE WAS DESIGNED BUT THIS PRESENTS CHALLENGES AS TO HOW THE CASTINGS THAT CLOSED OFF THE GAPS BETWEEN THE SUMP AND CRANKCASE AT THE FRONT AND REAR WERE CONFIGURED, THEREBY INCREASING THE NUMBER OF CRANKCASE CASTINGS.
THE STIFFENING RIBS SEEN SUPPORTING THE SEVEN MAIN BEARINGS ARE MASSIVE, CONTRIBUTING TO THE TORSIONAL STIFFNESS AND BEAM STRENGTH OF THE CRANKCASE.
ALSO NOTE THE MODERN OIL SEAL USED AT THE REAR OF THE CRANKSHAFT.
THE OTHER WAY IS TO HAVE THE CRANKCASE AS A SINGLE STRUCTURAL COMPONENT AND THE SUMP MERELY AS A CLOSING PLATE. THIS IS THE WAY THE 4 LITRE CRANKCASE WAS DESIGNED BUT THIS PRESENTS CHALLENGES AS TO HOW THE CASTINGS THAT CLOSED OFF THE GAPS BETWEEN THE SUMP AND CRANKCASE AT THE FRONT AND REAR WERE CONFIGURED, THEREBY INCREASING THE NUMBER OF CRANKCASE CASTINGS.
THE STIFFENING RIBS SEEN SUPPORTING THE SEVEN MAIN BEARINGS ARE MASSIVE, CONTRIBUTING TO THE TORSIONAL STIFFNESS AND BEAM STRENGTH OF THE CRANKCASE.
ALSO NOTE THE MODERN OIL SEAL USED AT THE REAR OF THE CRANKSHAFT.
ABOVE, THE CON RODS AND END PLATES INSTALLED. THE OIL PUMP IS IN THE BRASS CASING AT THE TOP RIGHT HAND SIDE. NOTE THE UNUSUAL ENGINE MOUNTINGS, THE ORIGINAL DESIGN CALLED FOR BRACKETS MOUNTED ON THE SIDE OF THE CRANKCASE TO SUPPORT THE ENGINE. THE BENTLEY DESIGNERS WERE OBVIOUSLY NOT HAPPY WITH THIS SOLUTION AND ASKED RICARDO FOR SUGGESTIONS AND THE RICARDO SUGGESTION THAT THEY RECEIVED WAS UNWORKABLE! THE DESIGN WAS ALTERED TO THE ABOVE CONFIGURATION AFTER BARRINGTON BECAME CHIEF ENGINEER.
ABOVE,THE SUMP AND FLYWHEEL COVER ADDED. NOTE THE BRONZE COVER TO ALLOW WORK ON THE OIL PUMP WITHOUT REMOVING THE SUMP. THE OTHER REMOVABLE PLATES ARE. ON THE LEFT, ACCESS TO THE OIL LEVEL FLOAT AND IN THE MIDDLE THE ACCESS TO THE VALVE FOR DRAINING THE OIL. THERE IS A FACILITY ON THE 4 LITRE ENGINE FOR DRAINING THE SUMP BY TURNING A LEVER SITUATED ON THE UPPER RIGHT HAND SIDE OF THE CRANKCASE. PROBABLY NOT THE SAFEST WAY TO DO THIS BUT THE BENTLEY DESIGNERS SURELY LOOKED INTO THE POSSIBILITIES OF THE FAILURE OF THE VALVE AND WERE CONFIDENT THAT THIS WOULD NOT HAPPEN.
ABOVE, THE BLOCK PREPARED FOR ASSEMBLY WITH THE CRANKCASE. THE BIG ENDS ARE TOO LARGE TO DROP STRAIGHT THROUGH THE 85MM BORES SO THAT THE PISTONS HAVE TO BE INSERTED FROM THE UNDERSIDE OF THE BLOCK WHICH HAS TO BE TILTED AT AN ANGLE WHEN PRESENTING TO THE CRANKCASE IN ORDER TO ALLOW THE CON RODS TO PASS THROUGH THE HOLES IN THE TOP OF THE CRANKCASE.
ABOVE, A VIEW OF THE RIGHT HAND SIDE OF THE ENGINE. AT THE LEFT IS THE TROUGH FOR THE STARTER MOTOR AND MOVING TO THE RIGHT THERE SEEMS TO BE SOME NON STANDARD OIL FILTER MOUNTED ON THE ORIGINAL ACCESS COVER TO THE BASKET TYPE ORIGINAL FILTER. ABOVE THIS FILTER CAN BE SEEN THE OIL DRAIN OPERATING LEVER. THEN THE ENCLOSED OIL LEVEL INDICATOR AND THEN THE OIL FILLER ASSEMBLY.
ABOVE, THE LEFT HAND SIDE OF THE ENGINE. THE DRIVE TO THE BOSCH DYNAMO AND WATER PUMP CAN BE SEEN ON THE LEFT, THIS USES BOSCH FUEL INJECTION FLANGES AND RUBBERS. THERE IS A HOLE THROUGH THE FLANGE TO ENABLE THE MOUNTING OF THE WATER PUMP AND PIPES.
ABOVE, THE REAR VIEW. THE VERTICAL SHAFT RUNNING FROM BEHIND THE BLOCK IS DRIVEN FROM A WORM GEAR AT THE REAR OF THE CAMSHAFT AND THIS SHAFT DRIVES THE BOSCH 6 CYLINDER DISTRIBUTER. ALL THE ELECTRICAL GEAR ON THIS ENGINE WAS SOURCED FROM BOSCH, EITHER BECAUSE THEY GOT A SPECIAL DEAL FROM BOSCH OR BARRINGTON CONSIDERED THAT THE BRITISH EQUIVALENTS WERE NOT UP TO THE SAME LEVEL OF QUALITY.
ABOVE, THE FRONT OF THE ENGINE.
THERE YOU ARE! THE 4 LITRE ENGINE IS A MUCH LESS COMPLICATED DESIGN THAN THE ORIGINAL WO BENTLEY INSPIRED ENGINES. AND MUCH CHEAPER TO RECONDITION AS WELL AS IT IS A MORE CONVENTIONAL DESIGN.
WELL THAT`S ALL I COULD SHOW YOU WITH THE PHOTOS THAT WERE AVAILABLE. I WILL BE PUTTING MY SPARE 4 LITRE ENGINE TOGETHER SOME TIME NEXT YEAR AND WILL DOCUMENT THAT MORE FULLY, WITH OF COURSE, THE BITSA BUILDERS MORE FRUGAL COST EFFECTIVE APPROACH.
NOT WRITTEN IN STONE IN THE BENTLEY DOGMA!! DUE TO ALL THE BENTLEY CHASSIS FOR THE DIFFERENT MODELS BEING VERY SIMILAR IN DESIGN AND DUE TO THE SIMILAR WIDTHS AND THE TAPER OF THE FRONT OF THE CHASSIS, THE 4 LITRE ENGINE WILL DROP INTO THE 3/4.5 CHASSIS IF THE RADIATOR IS PUSHED FORWARD BY 6 INCHES. ALTHOUGH TO GET THE CORRECT PROPORTIONS OF THE SIDE VIEW, THE ENGINE NEEDS TO BE PLACED 6 INCHES FURTHER TO THE REAR WITH THE RADIATOR IN IT`S ORIGINAL POSITION IN THE CHASSIS. WHICH MEANS THAT THE GEARBOX CHASSIS CROSSMEMBERS AND PEDALS etc. WILL NEED TO MOVED TO THE REAR AS WELL. YOU CAN SEE THE 4 LITRE ENGINE MOUNTED IN A 3 LITRE CHASSIS HERE.