I have the problem of gas spitting out the top of my weber 40IDFs. This is what I see looking down into the carb (with a mirror). The red arrow shows the fuel coming out the I believe is the spray nozzle. It hits the wall of the tube and spits up. What causes this.

What cam do you have in the car?

with wild cams sometime the piston is on the way up, the intake valve is still open. blowing some of the intake charge out of the carb.

Its called reversion. Taller air horns can help contain this..

Also the floats can be stuck, and the fuel pump is pushing gas right through the jets

oh yea.. Porsche went to the tall manifolds on the 911s' because of reversion.. I have apice somewhere showing the fuel charge above the air horn..

Gawd.....hope Martin Baker doesn't see this.....but he has mild cams, I think.

Have no idea what cam the PO put in. He did put a lot of hi-performace parts in. I have 3" velocity stacks and I have had the carbs apart an know the floats arent stuck. I even set the floats from 10mm to 14mm. I also had the problem of over rich mixture to the point of driving it 5 miles and the plugs foul. I had 50 idles and went to 40.

Has anyone one a clue