If you’ve ever had to send your vehicle’s or parts of that engine to a machine shop, it can feel like a black hole into which . Then, hopefully, if you picked a good shop, you get back a clean and straight set of cylinder heads or a nicely decked engine block.

Here’s the thing, though: what goes on in a machine shop is incredible. While they often look like dirty, greasy borderline junk piles with filthy old machines and filthier old men all over the place, the level of cleanliness and precision needed to perform even basic work is incredible. That’s why I’ve been borderline obsessed with videos from JAMSI (aka Jim’s Automotive Machine Shop, Inc. ) lately. This video, in particular, is fascinating because they take a severely damaged 4.2-liter Jag inline-six block and find a way to save it and likely their customer’s entire project.

As you’ll see in the video, this block has a bunch of corrosion and some pretty nasty cracking between the cylinders through the water jackets. The solution to this is to press in some new cylinder sleeves, but the operation is a whole lot more complicated than just breaking out the Harbor Freight press and a block of wood.

The video ends with the boring and honing phase, and the end result is pretty incredible as it also allows the vehicle owner to go back down to standard-size pistons and rings, meaning things will work like it did when it was new.

There are a ton of videos on the channel, and pretty much all of them are as interesting as this one, so check them out.