I drove 84-85 M10 318i cars for about a decade and found that 1) exhaust guide wallowing, 2) oil pump, and 3) rod bearings all needed a refresh at about 175-200K.
The early (1984) M10 318i had a problem whereby the idle shot up on start-up and trashed the rod bearings over time. Your E21 had CIS on it so maybe that was not a problem.
I would check the oil pump (just need feeler gauges) and have the machinist look for ova-led/wallowed exhaust guides.
The engines are very durable - I would call these items maintenance. I have seen engines well past 225K with no ridge on the cylinders come back to life after a head refresh. Many engines will blow the bottom end out upon a head refresh (the tight new head can stress the bottom end beyond it's higher mileage limits).
The early (1984) M10 318i had a problem whereby the idle shot up on start-up and trashed the rod bearings over time. Your E21 had CIS on it so maybe that was not a problem.
I would check the oil pump (just need feeler gauges) and have the machinist look for ova-led/wallowed exhaust guides.
The engines are very durable - I would call these items maintenance. I have seen engines well past 225K with no ridge on the cylinders come back to life after a head refresh. Many engines will blow the bottom end out upon a head refresh (the tight new head can stress the bottom end beyond it's higher mileage limits).
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