Is it possible to just drop the pan and change out the main and rod bearings on the lower end of a 1.6L CS diesel from a 1982 Vanagon? I heave heard that it has to be done by a machine shop to be “line boarded” to do it right and avoid “spinning a bearing”.
It could be done like that but to just drop a pan and add a set of bearings you should really have a few specialty tools and know what you’re doing. It would also take a bit of luck.
Since it’s assumed the engine is high mileage, and gone through a lot of high compression diesel stress, there is a good chance the crank journals have some wear that is putting them out of specification.
This means out of round, taper, etc.
You would have to clean and carefully mike every journal in multiple locations to know this.
The line-boring that is referred to is often in regards to the opposed 4 cylinder gas engines. The bearings are harder than the engine block and over time can wallow out the engine block main bearing saddles.
You could just throw a set of bearings in it but if the crank journals are out of whack then the life expectancy of the new bearings will not be that long, especially considering it’s a diesel.
If the journals are out of spec then the only proper way is to remove the crankshaft (engine out) and have it reground.
As an alternative, you could just buy a remanufactured engine for about $1500:
Part of it depends on your reason for wanting to do it. If it’s only for low oil pressure, replacing the bearings this way couldn’t hurt. If it’s a knock, forget this way.