I have a 1987 740 with the b230f. Last year I bought the car from the original owner with 200,000 miles. He did the noble thing - invest 3 times the value of the car at the dealer over the years until finally, a few years ago he said enough. Thinking the car would just die - he kept driving it. Not wanting to die, I think he tried to murder it - but making it look like a suicide. No luck.

Finally he just hung a for sale sign on the car and I picked it up for $500.

The injectors (we hypothesized) leaked gas into the cylinders, thus thinning the oil and causing excessive wear on the crankshaft bearings. Having a knock, we pulled the engine, removed the crankshaft and machined it - then went 1 size up on oversize bearings. We put it back together, replaced all the seals and timing belt hardware and new injector seals and good as new!