Quote:
Originally Posted by StanJ
Just to clarify --
The "caps" you're referring to aren't a means of eliminating the power valves; they are baffles which keep the power valve's fuel entry ports from becoming uncovered during hard cornering. In the case of the carb in question, the PVCR's in both metering blocks are .063" in diameter, which equates to roughly nine jet #'s worth of fuel metered inlet area -- quite a bit to lose...even momentarily...when the PV's start sucking air.
Jet extensions on a road car are almost never needed if fuel control issues in the float bowl are properly addressed. More to the point however, they often cause problems (engine stalling) of their own upon hard braking. For years, the "catch 22" was that if your engine made enough power...and your chassis and tires could hook that power to the ground...and your driver didn't run low on talent, then a car that truly benefited from jet extensions under acceleration would suffer a like amount from them on braking. The true solution to the problem -- metering blocks with lowered jet locations and float bowls designed with a "sump" to accommodate them -- didn't come around until just a few years ago.
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Interesting comment about the jet extensions. My Quick Fuel carb has them, but only on the secondaries. Presumably on braking the secondaries are closed so lack of gas doesn't hurt? I'll be interested to see on track days if the primaries go dry under sustained braking.