Final preparation for assembly on our 4.6L Jeep XJ engine - Hagerty Media

The light has appeared at the end of the tunnel for Davin and the Jeep engine. It’s still quite far away, but he can see it. Before taking steps toward that light, another trip to the Thirlby machine shop is required to lower the deck height in an effort to raise the compression. And another issue pops up that needs to be discussed with the machinists.

Before loading up and heading off to re-deck the block, Davin takes the time to check the oil clearance on the main bearings. This is an important step, because while most of the time the numbers come out fine, engine building is always a game of “trust, but verify.” With the main caps torqued to spec, Davin measures the diameter of the bearing location on three axis. What he finds is a little uncomfortable. To him, the holes seem a little egg-shaped and also about half a thousandth too wide.

The machine shop doesn’t agree, however. Before bolting the block into the machine to trim the deck down, they use thier measuring tools to “sanity check” Davin, and they certifiy him insane. Davin is a known perfectionist, and on this job the machine shop guys think he might be going just a bit too far. The return on investment of getting this absolutely perfect is pretty slim, and that’s why they advise it would be best to leave this one alone. Those clearances might be a fraction off, but they’re still well within a usable tolerance.

Back at the shop, Davin is the first to admit things are way out of order at this point. A freshly painted block shouldn’t be going to a machine shop, and a block back from the machine shop shouldn’t be getting casting cleaned up again. It makes for even more cleaning work before assembly can begin, but we all know Davin is not one to take the easy route just to get things done. With any luck, things will come together next week, but then again, another roadblock might also appear. To find out for yourself, be sure to subscribe to the Hagerty YouTube channel to never miss an update.

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