Drilling Webbers

[RMartin]

In Bruce Andersons 911 performance hand book he mentions that PMO sells a jig to drill Webber carbs so that fuel will not boil in the float bowls. Has anyone used this jig? Will this modification work?

[RoninLB]

the jig works. You should also have head to maifold insulator spacers.

[randywebb]

there is a whole series of upgrades to Webers - contact PMO for help and read BA's book closely

[jluetjen]

Personally, I just punched a starter hole (notch?) and drilled them with a standard hand-held drill. I showed them to Matt at Eurometrix and he said that they looked fine. I haven't run them yet since they are sitting on my bench waiting for the rest of the engine go go together...

[911pcars]

Actually, the holes allow pressure inside the float bowl to vent to atmosphere via the carb throat. Without the holes, percolating fuel can be forced out of the bowl through the discharge tube and flood the engine.

This modification is used in conjunction with insulating spacers under the manifolds and anything else you can think of to prevent heat soak from affecting the fuel level. Even a timed or thermostatically-controlled fan (after engine shut off) under the engine lid would help.

Sherwood

[RMartin]

Anyone got a pic of exactly where to drill the holes and what size hole?

[jluetjen]

Bruce Anderson's (911 Performance Handbook) has a number of them. If you're doing stuff like this, you should have a copy of that book as well as Wayne's.