What is the best way to clean the oil passages in an engine block?

I have an older vehicle and I need to do an oil change on it, but because the person who had the vehicle before me mounted a cross member across the drain plug, i want to make sure that i get any build up out of the block since i have to pull the engine to get the drain plug off. i don't want to pull the engine, change the oil, and put the engine back just to find out that i need to pull it again to clear the passages. I can't just remove the cross member because it is mounted to the engine mounts.What is the best way to clean the oil passages in an engine block?
you didn't mention whether or not you are disassembling the engine when removed from the vehicle or not. if dissassembling then vat the block at machine shop with all oil galley plugs removed, then take to local carwash and spray directly through all galley holes, then dry throughly with compressed air and reinstall plugs and assemble engine. if not disassembling then marvel mystery oil( which can be purchased almost anywhere that sell lubricants)can be added to the engine oil per directions on the can. i'm 50 years old and this product has been around since i was old enough to know how to read and does do what it says when used accordingly. while i had the engine out you might consider installing a quick drain petcock or relocating your drain plug to another location that is easier to access without having to pull the engine every timeWhat is the best way to clean the oil passages in an engine block?
run marvil mystery oil in it for a few miles before you change the oil. That or something similar. That's the best you can do without taking things apart.
Beware of solvent based products, Eats seals and can damage bearings.


Add Marvel Mystery Oil to a pre-warmed engine added to just and I mean just over the full mark on the dip stick the run engine at about 2000 RPM for a couple of minutes no more then drain while still warm.