Always been one of my fears when removing these inlet manifolds. Consequently, I put a piece of rag in the hole.
I'm interested in the comment about the tube not being a breather but a return line to the sump.
One of the manuals I have describes its purpose as venting crankcase vapour into the inlet manifold to be burnt.
If it were a return line for oil from the head, how does the oil from the head get into it?
There are oilways from the head into the block as with any motor .
The only other way oil could pass from the head is through the ventilation hose on the rocker cover. My inderstanding is that vapour from under the rocker cover passes into the intake manifold to be burnt. Try disconnecting the hose with the motor running. It will almost stall as the manifild pressure increases to approach atmospheric.
