Oil leak guidance

[xpensivewino]

Mating Surface preparation is often a determining factor in leaks. Case halves, and certainly valve covers need to be “freshly machined” flat to assure minimal leaks. Certainly sealing materials make a difference as well. I generally follow Henry’s sealant advice on my builds and have very good results. Proper torque specs are important as well, people almost always way over tighten valve covers and actually cause leaks. As far as the gearbox goes, I only run dino-oil in mine as per Tony Gerace’s advice. Synthetics, although good for internals, can sometimes leak more so than standard oils. Unfortunately when your engine and gearbox are already complete, much of this advice is hindsight, but you may be able to cure a few by checking these common issues.

[911TES]

I would clean the engine as well as practical followed by a fluorescent oil additive detectable with UV.

Amazon:
ACDelco 1148963 GM Original Equipment 10-5045 Multi-Purpose Fluorescent Leak Detection Dye - 1 oz

I haven’t used it, but it’s highly rated and likely a lot of tips within the reviews.
There’s a corresponding UV flashlight and safety glasses to filter the UV to protect your eyes. The UV will be UV-A so not particularly harmful, but use the glasses anyway. The fluoresced light will be a bright visible color, in this case, orange. (The glasses are to protect your eyes from reflected UV, not to see the fluorescing oil).
Let us know how it works. I might try it on my ‘66 Triumph motorcycle engine.