01-09-2018, 11:52 PM
Cylinder wear is a very unreliable indicator of wear. At full operating temp wear is and was virtually nil. Many Sevens were used primarily for short runs and in cold climates would have run very cold. There seems to have been a major change in the 1950s presumably due API SB and better rated oils. Until then light cars were commonly rebored at low mileage. Even the likes of A40s were often reconditioned at 60,000 or so. The minimum overbore often not adopted; I suspect the first factory oversize was 1/32 (near .030). Reconditioners favour use of pistons they chanced to have in stock.
My RP was rebored about 1939 at 40,000 miles and , with both extensive main road and very short runs, was a very worn .010 taper 60,000 later about 1957 (but not burning a lot of oil!). At 110,000 and much hill work there was some pitting of the pinion, possibly promoted by non optimum adjustment. Comparison with other old gearboxes seems to suggest these have done several times the mileage!
Mileage varies enormously car to car and with different owners. Few did regular long trips in Sevens but reasonably long daily commutes pile on the miles. Here towns and cities were smaller and drivers who do 10,000 pa did 3,000.
It is also difficult to judge from general wear. Many older cars in later life were not regularly greased so wear through the spring bushes etc does not necessarily indicate vast mileage.
(Incidentally whilst many use expensive oils, change frequently, fit filters, etc presumably in pursuit of nil wear I have read of no one advocating for a thermostat. Even Bradfords, which run hot anyway, had these.
My RP was rebored about 1939 at 40,000 miles and , with both extensive main road and very short runs, was a very worn .010 taper 60,000 later about 1957 (but not burning a lot of oil!). At 110,000 and much hill work there was some pitting of the pinion, possibly promoted by non optimum adjustment. Comparison with other old gearboxes seems to suggest these have done several times the mileage!
Mileage varies enormously car to car and with different owners. Few did regular long trips in Sevens but reasonably long daily commutes pile on the miles. Here towns and cities were smaller and drivers who do 10,000 pa did 3,000.
It is also difficult to judge from general wear. Many older cars in later life were not regularly greased so wear through the spring bushes etc does not necessarily indicate vast mileage.
(Incidentally whilst many use expensive oils, change frequently, fit filters, etc presumably in pursuit of nil wear I have read of no one advocating for a thermostat. Even Bradfords, which run hot anyway, had these.