That's why both Continental and Lycoming specify that cylinder deck studs and through bolts should be torqued “wet” (by applying lubricant to the fasteners) to reduce these frictional losses and increase the preload achieved by torqueing to a specified value.

Obstacles to proper preload

Roger Fuchs identified five obstacles to achieving proper fastener preload when performing cylinder installation on an engine mounted in the airplane:

1. The fasteners aren't new. When an engine is initially assembled at the factory (or by a first-rate overhaul shop), the through bolts, deck studs, and cylinder hold-down nuts are all brand-new with cadmium-plated threads in perfect condition. The cad plating is very slippery (helping to reduce friction) but very thin (typically 8 microns thick, one-tenth the thickness of a human hair) and relatively soft, making it easy to damage.

2. Fasteners may not be adequately lubricated. Both Continental and Lycoming specify that cylinder fasteners are to be torqued wet. Continental calls for using 50-weight engine oil, while Lycoming suggests using a 90/10 mixture of engine oil and STP additive. To achieve proper preload, the lubricant needs to be slathered onto both the fastener threads and the nut face area.

3. The lubricant itself is rather poor. Fuchs also pointed out that plain 50-weight engine oil (e.g., Aeroshell W100) is a lousy thread lubricant because it lacks synthetics and anti-wear additives that would make it much slipperier. Add this to the likely loss of slippery cad plating from the worn fastener threads, not to mention the possibility of thread damage, and it's anybody's guess whether proper torque will result in proper preload.

4. Wrench access is limited. Both Continental and Lycoming call for a two-phase tightening procedure where all the cylinder hold-down nuts are first torqued to 50 percent of their final torque in a specified tightening sequence, and then they are torqued to 100 percent of their final torque following the same sequence.

5. Manufacturer instructions are incomplete. The published guidance from Continental and Lycoming leaves a lot to be desired. For example, Continental's overhaul manuals emphasize that when a cylinder is replaced, the nuts on both ends of each through bolt must be torqued. Many mechanics ignore this and don't bother with torqueing the nut on the opposite side of the engine. But even if they do, there's nothing in Continental's guidance suggesting that the opposite-side nut should be removed and the nut and threads be lubricated, nor that the opposite-side threads should be cleaned and the opposite-side nut be replaced with a new one. It's dubious that following Continental's published guidance will accomplish anything useful regarding torqueing the opposite-side nut—which is probably why so many mechanics don't even bother with it unless they're also replacing the opposite-side cylinder.

https://www.aopa.org/news-and-media/all-news/2020/march/pilot/savvy-maintenance-risky-business