Oil consumption

[peterg]

After getting my engine rebuilt four years ago by a major Bristol specialist and finally taking it for a long run I am absolutely gobsmacked to find that it is burning one pint of oil per forty miles.

After checking through my invoices I found that, although the engine was totally dismantled and checked the pistons were left in situ.

My question is could this level of oil consumption be caused by worn valves or am I looking at replacement pistons and another engine rebuild?