Fuel Consumption

[RarlyL8]

Without going into too much thread hijacking detail, the fuel head has a stack of shims or washers in the fuel inlet bung that can be added to or removed from resulting in a change in system fuel pressure. This only needs to be done if your system pressure is off-spec (usually low) or you pass the 400HP level. You need to have your system pressure in-spec in order for the WUR to operate optimally and before you make any changes to the WUR. When you pass the 400HP level you should increase your system pressure above factory spec and adjust the WUR in concert. These 2 components work together to give you the precise pressures and flow necessary to support more power while starting and running smoothly. Once the CIS is dialed in you can address cam timing, gearing and other components that will increase fuel mileage.

[Craig 930 RS]

That's what I thought.

Early attempts at fuel head modifications, in my case, resulted in an engine much too lean in the top 1/4.

Mine was shimmed on the previous rebuild.

As on any of this stuff, YMMV so take general advice and MONITOR, monitor, MoNiToR those AFRs....

[RarlyL8]

The A/F ratio would be lean on top if (a) the system pressure was too low for your power output or (b) the WUR boost pressure was not adjusted properly or (c) both. This would all be revealed on a dyno run or with an LM1.

[Craig 930 RS]

Good points -