When Davin heard that the next project rolling throught his door would be a red two-door with a stick shift, he had dreams of Bel Airs and Chevelles. He wasn’t so lucky. No matter. He can put a hot rodder touch on just about any engine, and the Jeep 4.0-liter power plant was no exception.

This ride came from Colorado and was in surprisingly good shape for a 150,000-mile chassis. The tired engine needed some help though, so Davin got right to work.

“Interestingly, this is one of the newer engines we’ve worked on, based on production date,” Davin says about the inline-six, “but the design traces back to the mid ’60s in AMC products. That is a darn long life.” It certainly is, and it’s because the 4.0-liter is designed around durability rather than performance. Even the “high-output” version that came in our Jeep is rated for just 190 horsepower. Davin figured he could do better than that.

As the engine was being torn down, there was little in the way of bad news. Although the engine indeed looked as though it had 150,000 miles, it was not abused. Combined with the extensive Rock Auto parts catalog at Davin’s fingertips and suddenly things got out of hand. Davin started looking at swapping around some parts from a 4.2-liter inline-six, and before we knew what had happened there was a new crankshaft, pistons, and connecting rods sitting on the table that would punch this engine out to 4.6 liters of displacement.

If only it were that easy. As with any engine, this one was being built, not assembled. That means paying careful attention to detail to ensure that all the parts play nicely together and the final result is exactly what was planned. In Davin’s case, everything fit together well, but “good enough” is not good enough for Davin. The compression ration came in under what was intially projected, based on the product specs, so the painted and dressed engine block took a second trip to the machine shop to get an additional 20-thousandths of an inch machined off the deck.

Then came final assembly. With everything together, the yet-to-be-started engine went back into the chassis. Longtime viewers of Davin’s work know he usually likes to break in engines on a test stand, but with the computer-controlled and emissions-connected 4.0-liter, it was easier to reinstall the engine first. Evend the distributor was installed correctly so that it fired right up for the 20-minute break-in.

“It drives really nice. Has a great punch right off idle,” Davin says about the fresh engine. “I really like how it came out and would certainly build another engine like it. Not much to change here, and it went together pretty easy.”

Well, if Davin says it’s good, you know it’s good. Now the Redline Garage has a bright red parts runner with a little more horsepower than stock—in other words, a perfect new addition to the fleet.

The next timelapse rebuild project might be one that viewers recognize, but that’s all we are allowed to say for now. To get the full story, you’ll have to subscribe and stay tuned for the next Redline Rebuild episode to see what Davin is getting his hands dirty on.

— Kyle Smith

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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