I have been given the use of a 1931 seven. The engine is about 15 years or so old and was decabonized and had the valves ground in about 6000 miled ago..It is going beautifully,and has great oil pressure, but I am intrigued,It uses about a pint of oil every 100/120 miles if I drive it hard on longish journey, and little or nothing about town But it smokes intermittently and for apparent reason. I use a good quality 20/50 oil and it is not overfilled.I have nothing to worry about ,Have I ?

No! you really don't have too much to worry about. Often on a long run oil useage can be attributed to oil loss ( drips etc ) rather than use ( burning in the engine ) as the oil is thinner the hotter the engine gets.

A pint of oil is certainly not excessive but could be better. When you say it smokes intermittently you may need to be more precise for anyone to offer accurate advice. Often engines will smoke after a long downhill run where the throttle has been closed and is then opened up. I can well remember being in a convoy of A7s running down the steep hill at Goring to the traffic lights at the bottom of the hill. When we pulled away the traffic lights disappeared in a blue fog. None of the cars had particularly shown signs of excessive oil burning but going down that hill in a low gear with no throttle had sucked oil from anywhere into the engines.

Enjoy your car and carry that spare pint of oil, next time the engine is out check the bores for signs of wear.

Perhaps it would be better to go for a straight 30 or 40 grade mineral oil as used originally. 20/50 can be a bit thin for a well run in engine. My 1928 Chummy uses (or loses) a similar amount of oil but is less of a problem now that I have changed to a 40 grade for summer (assuming that we get one this year
All the best
Brian Hutchings