Standing a long time and lack of lubrication.
My 2c had stood 21 years and although it was checked over (not Stripped) by the person doing the restoration, on my way home after collection with only 27K miles on the clock, it was running ok and not making any nasty noises, but after about 50 miles it started covering the windscreen of my wife's car behind me with an oil mist, it still seemed to be running ok so we carried on,when I got home I had it checked and a broken piston ring and scored a bore was found, necessitating a complete strip down, rebore and oversize pistons, not cheap

If the engine hadn't been stripped and you've got away without a scored bore, I think you've been very lucky.
Brian
8227
