Originally Posted by
LarrBeard
Several of us have found, the hard way, that the original Carter YF and WO carburetors really want to see a fairly low fuel pressure, 1 - 2 PSI. That delivers plenty of fuel to the L/F-134 engines.
What happens on occasion is that new or rebuilt fuel pumps are too good - they can deliver 8 - 10 PSI and that's just more than the YF/WO wants to handle. Adding a spacer under the fuel pump is a patch that isn't a good idea - it adds a "thump/clunk/clack" when the cam hits the lever on the pump.
I have a F-134 in the '48 and as part of the trials and tribulations in waking it up again I added a fuel pressure regulator between the new/rebuilt fuel pump and the carb. It's set for about 1.5 PSI and I've had no issues related to fuel pressure since I put it in. The attached photo shows the rig we set up to measure fuel pressure. The gauge says 1.5 and that's where we left it.