The design’s getting on a bit now, but that is also the BD’s strength.
Photo Jon Hill
Original BD problems are mainly due to age although everything’s now available — Wilcox has a massive inventory meaning engines can be completely built with brand new parts off the shelf.
It’s unlikely you’ll find an untouched engine either — unless the history of the engine’s known everything needs to be treated as if it needs a rebuild. However, it pays to stick with a reputable builder whom will know what’s in the engine.
Most weaknesses are known and have been overcome — an early cam carrier for example may crack across the exhaust — these are now beefed up as castings, whilst Wilcox used to perform their own modification here. Cracks at the bottom of the liners are not uncommon. This usually means that the block is split between the liners allowing the bores to become oval and scraping the block.
Head gasket problems are also a thing of the past thanks to multi-layer gaskets — Wilcox has its own design.