Actually, the Bentley manuals for Audi, VW, and BMWs, for example, list the cylinder compression specifications. I remember testing the compression on my '89 VW GTI and gotten very close to the specs.

However, many things could produce false compression reading. Having too much carbon deposits, for instance, could raise the effective compression ratio such that you get a high reading on the compression test, but in actual running the engine EFI controller would retard the timing to compensate for the higher CR to prevent detonation. The result being substantially reduced power.

Then there are the typical difference between static compression and dynamic compression. Air is a low viscocity fluid, but it does have a viscocity. This means that at higher RPMs the combustion gasses cannot escape through the tiny leak around the piston rings as easily as with the engine running at low RPMs. This is why a tired old engine might have almost as much power at the top end, but just wouldn't idle worth a s**t.

Then there are those pesky dykes rings that rely on combustion pressure to achieve an effective ring seal. With those, you won't see much compression just spinning it with a starter.

Our RC engines are typically too small and not manufactured to high enough of a tolerance for the manufacturer to publish a factory spec, which can be used as a reference. Plus, if we are talking about ABC engine, forget it. Unless it is at operating temp, the compression gauge readings are just about meaningless.