Weber 40's on a 807

[BERNIEHUMBER]

HI:
There will be two 40 Webers going on a 807 and I was wondering about the purpose of an opening in the carb(s)?
I have included a pic with an arrow to the opening.
The carbs had air horns so what ever its function that didn't get in the way by being ignored.
Thanks

[Richard48Y]

Fuel vent.

[bjthomp]

The float bowl air vent you've pictured is typically within an air box or filter housing. It is thus so the air that flows into the vent is filtered and doesn't contaminate the fuel and jets in and above the float bowl. If you are going to refit air horns, the vent opening needs to have a filter, typically a cylindrical sponge material. I've seen them supplied with foam air filter sock kits that go over air horns.

[jbcollier]

Needs to open to the air.  Don’t block it off.

[BERNIEHUMBER]

HI:
Thanks for the input.
The 45 I have on a 1470 has a filter box that includes the vent within the filter box itself.