Ever since the rebuilt, my 1600 was leaking oil at a rate of nearly a liter every month, for some obscure reasons, bad assembly, defective seals? Who knows...
Anyway. I had the engine tuned-up back in april and noted that oil leakage has dropped sharply, despite running on synthetic. Indeed, I poured-in the first liter about a month ago.
My mechanics could not readily explain this but we eventually traced the source of the remedy : at the tune-up time, he put back on that hose that connect the oil filler tube to the air filter intake. That hose was overlooked at rebuilt time in 2001. I initially figured it to be optional and since I had no oil spill at the open tube and the car ran well.
The vaccum created by the air intake would keep the oil inside the case instead of letting it go down the crack/leak.
I thought that my story could help someone else, hence my posting :)