Lynn, Dave nailed it, the 21 stud heads indicate a 221ci 85hp engine. The earlier Post-war Pilots had the 17 stud V8-60, but these are relatively rare.
Wikipedia calls the engine the E71A, but that is the model number for the car itself. AFAIK, the engine has always been called the E77, the English-made version of the US Model 77, or '37 LB engine. Again, Wikipedia says it was a version of the Model 78 Truck engine, but this had twin pulleys and a different cam to the 77, and was not the "inspiration" for the English engine.
Always in Pilot cars, (and even in Thames trucks when dual pulleys
were used), the engine was a copy of the 77 (1937) US car engine, even down to the 18mm spark plugs.