We just wrapped up rebuilding our 1965 Mini Cooper S 11275cc engine. It was a journey of trial and error throughout the process, so, join Davin and Ben as they break down what it took to get this little monster running again.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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Enjoy 1965 Mini Cooper S stories, opinion, and features from across the car world - Hagerty Media

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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.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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Enjoy 1965 Mini Cooper S stories, opinion, and features from across the car world - Hagerty Media

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The Redline Rebuild garage is no stranger to interesting discoveries during engine disassembly, but the 1965 Mini has some new ones for Davin. Remember, the car drove itself into the shop, but that doesn’t mean everything inside the tidy four-cylinder is just peachy. It’s proving to be quite the opposite.

This Mini put up a maxi fight when asked to give up its engine and transmission, but with that task finally completed, it’s time for Davin to tear into the engine and get a better look at exactly what he’s working with. Compared to a few of the previous projects—like the Buick Nailhead—this engine (once out of the car) was practically giving up its parts. Fasteners backed right out and things split apart easily. Too easily. Then Davin found the thermostat and got a hint of what may be hiding inside.

“The thermostat had been gutted in what I think was an attempt to help with an overheating problem,” Davin says, looking over the greasy parts on a workbench. “It’s a common thing I see, but it’s only a bandaid and often a bad one at that.” The thought is to improve coolant flow and thus dump more heat via the radiator. Sadly, the increase speed of coolant through the block often means it actually picks up less heat while flowing through coolant passages. That’s just the first sign of bad news.

Things get more interesting when the cylinder head and gasket are removed. Two fissures on the deck surface of the block appear to be from a leaking headgasket. Combustion heat and pressure can erode the aluminum or cast iron of a block. Is there enough material left that this block can be machined flat and still be used? Davin isn’t sure, but he has his fingers crossed. If you want to find out, you’ll have to subscribe to the Hagerty YouTube channel and watch a future episode of Redline Update.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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