Originally Posted by turk1
You still ignore that at WOT there is nearly no suction to make atmosphere pressure open the needle from seat to make pump to be able to feed carb.
At glow application, that no suction line fed by pressurized tank,not spray bar suction.So Gravity King s case was as expected.
At Walbro, there is venturi suction to make regulator needle open the fuel pump line to feed the engine at WOT.
The engine does run at WOT, so negative pressure inside the venturi does exist.
But a WT style carb has 4 ports that supply negative pressure to the float diaphragm, and
the pop - off is 50 psi. NGH carb has only one port.
The WYK series is a barrel valve carb, and has only 1 port that supplies negative pressure
to the float diaphragm, it has a really small main jet (aprox. .018" dia.) and the pop - off is 30 psi.
I have mentioned before that a balance is required between float diaphragm and the carburetor.
Changing the spring rate may assist that balance, but I don't believe it is the only thing that needs to