My own 74, bought in 74 still has its original B20, with internals that mostly came with it. Two months ago, while attempting to replace the timing gear, the tip of the camshaft broke, prompting for an unschedule teardown of the engine. As we pulled the engine apart, all it needed was a set of rings and lifters (not that it needed it, but since we were already there...), valve seals, and gaskets. All of the internals went in without needing any machining, and the cam lobes were still within specs. The cylinder bores were excellent, with no ridge on the top of each bore, something you would see on lesser engines after so many miles. The odometer died a few years ago at 280K miles, so I am guessing that I am well over 300Kmiles at the time of the rebuild.

Besides having hardened valve seats, the 74 also has the larger wristpins, 8 bolt crank, as well as a reinforced block.

After 32 years and some 300K miles later, to say that the 74 is often troublesome is not exactly my choice of words to describe this particular version of the B20. The only times it failed to start was once in every few years. When the battery was flat.
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...and the bricks keep on rolling