Trying to sort my mates Jeffrey JS5 which has a pre-crossflow 1500 running a Weber 28/36 downdraft.
The inlet has a hole in the base which goes to atmosphere.
The hole looks intentional as it has a brass seat.
What is it for and should it be open to atmosphere?

28 36 manifold

PS - Anyone got a pre-crossflow manifold and twin 40's?

I believe it used to be common practice. It's a drain in case of flooding. My 2CV has one and I'm sure I remember them on some of the bangers in the dim and distant

Is there a barbed fitting on the bottom of the manifold for a rubber hose? If not, did there used to be one and it's been snapped off at some point?

Don't know if there was any fitting on the bottom but unlikely as the hole is very close to the exhaust manifold (It's a pre-crossflow therefore exhaust is on same side as carb).
I'll need to take the manifold off and have a closer look.

[Edited on 31/8/11 by minitici]

Have vague memories of a copper pipe vented to the atmosphere on some pre crossflow engine . Long time since I worked on one though