Taking our 4.0L XJ Engine to the machine shop | Redline Update - Hagerty Media
It’s a new week, but it’s the same ol’ story in the Redline Garage. The Jeep 4.0-liter is torn down to a bare block, which means it’s time for a field trip to Thirlby machine shop. This block might represent the best starting point Davin has ever carried through the machine shop door. Of course, that doesn’t mean there’s any less work ahead for the team
“Everything was in really great shape,” said Davin after returning with the freshly machined parts. “We could have just honed it and thrown it back together. Just not worth it though. I mean, you’re already there.” What he’s getting at here is that the engine is already torn down, so there is no point putting off a job now that will only be harder later. The 150,000-mile block didn’t suffer oval-shaped cylinders or any other signs of terrible shape, but it still made sense to spend the few hundred dollars and give it the full machine shop treatment. From the deep clean to the decking and boring, this block is better than new.
There are other parts of the Jeep that need that same better-than-new treatment, and the flywheel is one of them. The starter engages a geared ring on the flywheel to start the engine, and the ring often wears out in just one spot. The reason has to do with the physics of how an engine stops when the ignition is turned off, and which cylinder ends up on the compression stroke to stop the rotation of the crankshaft. The ring gear here could just be flipped, but pressing on a new one that will last a long time is easy enough once we are already in there.
Next stop is the paint booth, but before the engine gets there Davin puts some color on the block along with some other parts on which he plans to do some clean-up work. Casting burrs and sharp edges can make even the nicest paint job look grungy—and when has Davin ever been one to cut corners?
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