Because I stupidly put the dizzy skew gear on back to front on my RRC 3.9, I am right now pulling the front off the engine AGAIN!!! probably it will not hurt but I would always be wondering.
ANYWAY, before I replaced the head gaskets I always had a wet spot on the LH front of the engine. And I am sure you know how uncomfortable wet spots are.
I always thought it was from the end seal of the valley and some probably was but when I looked today, the wall in front of the seal was dry , but a big pool on the timing cover, after only say 1500Km.
The oil was coming up the dizzy shaft via the Oring.
I have now put on a new Oring by holding my tongue right while using 3 hands to slip it over the skew gear.
So , if you have an engine oil leak, or are just changing head gaskets where you take out the dizzy put a new Oring on.
Regards Philip A