The engine for our 1965 Mini Cooper S may be bored, but we’ve never been more engaged. This week Davin heads over to Thirlby’s Machine Shop to get this 1275cc British rocket cleaned up and (nearly) back to its original shape. We had some concerns about what we unearthed last week on the block, but it’s up to the boys at Thirlby’s to diagnose the severity of the damage. Happily, luck proves to be on Davin’s side.

This may be the first time in a while that Davin doesn’t need a hoist to drop pieces off at the machine shop. Both the cylinder head and engine block are easily carried in by hand for the first step: cleaning. Each piece has pressed-in brass plugs that must be knocked out before both components are baked to remove the old paint and built-up grime. Rather than open up the cylinder head, though, Davin decides to simply tumble it, fearing he may not be able to replace the brass plugs with pipe plugs after cleaning.

Once the head and block are looking spiffy, it’s time to check for cracks. No cracks found means it’s time to start cutting iron. The cylinder head gets its valve guides knurled and machined to size before new valve seats are pressed in and cut. That’s the easy stuff, though—the block is the main worry. With a larger arsenal of measuring tools than Davin, the Thirlby crew takes a look and devises a plan that they think will save this block with no extra work.

The bore is cut to 40 thousandths of an inch larger, which removes a sizable portion of the two eroded sections of the deck. Next, that deck surface is machined flat. Just 14 thousandths of an inch is removed here, which succeeds in cleaning up the mess Davin found. That 14 thousandths is just over half of the 25 we had to play with, so this block should happily live on and could likely even be machined again in the future should the need arise.

Right out of the machine shop, the parts go into the paint booth. Some taping off and a thorough wipe-down with wax and grease remover preps the lot for a quick spray of dark green that Davin has mixed up to match the color he spied under the grease and grime of the block. Once the paint has cured, it’s back to the Redline Garage to begin final cleaning and assembly. Of course, there are a lot of interesting pieces and processes to talk about there, but you will have to tune in to future Redline Updates to see those. Until then, be sure to keep working on your own projects, and subscribe to the Hagerty YouTube channel to never miss an update.

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