Percofix

The “Percofix kit” is a modification designed to address the issue of fuel percolation (boiling) in Weber carburetors on Porsche 911s, particularly during hot starts or heat soak after the engine is turned off. It usually involves drilling a small vent hole in a specific location in the carburetor body to relieve pressure from the float bowl.

Purpose and Function

Problem: After a hot engine is shut down, residual heat can cause the fuel in the carburetor’s float bowls to boil and expand, forcing excess fuel through the main discharge tube and into the engine’s intake manifold (percolation). This results in flooding, which makes the car very difficult to restart when hot.

Solution: The PMO Percofix kit (or similar anti-percolation modifications) provides a fixture or guide for drilling an angled vent path from the air horn area into the float bowl. This vent relieves the pressure build-up caused by the expanding fuel vapor, preventing the fuel from being pushed into the manifold and thus eliminating the hot-start issues.

Drilling Process

The modification typically involves using a specialized drill bit and guide (the “kit”) to create the vent hole in a precise location.
The specific instructions and precise location That is why we have a drill bit and the jig
The goal is to allow the fuel vapor pressure to escape harmlessly rather than forcing fuel into the engine’s intake.