Join Date: Jul 2006
Location: Northfield, Illinois
There IS a catch. The latest Viton fuel proof diaphragm is a bit stiffer than the original. If you have an original diaphragm in there and have run with todays "fuel" it will harden, stiffen and eventually crack and leak. If it's original, and pressure is high, you need a new diaphragm.
The new Viton version being stiffer than the original, may also be a bit high. Unfortunately, the adjustment screw will only give about 1# pressure adjustment, + or - on a FISPA FRB 11. Get as close to 3# at idle as you can, and call it good. I recently restored one on a Ferrari, and ended up adjusting it just to maintain extended periods at idle, using the Ferrari FISPA mechanical pump only (no electric pump) for fill pressure / volume. Fuel level in the bowls would drop, mixture lean and then rough or no idle. My suspicion here is the fuel pump may be tired.
Too much pressure will overwhelm DCOE 26gram floats with big needles and seats causing flooding. Too little and you will have low float bowl fuel levels and issues like the Ferrari.
Alfa's Webers like 3# at idle, maybe 3.5#. Not more. If you are running 2.0 needles and seats with Webers with brass floats, 3# is better. Plastic float Spanish Webers will handle more with 2.0 N & S. Most Alfa applications under 2L or non racing use 1.75 N & S with brass floats. Plastic float Webers have different float axle position, and heavier floats and you can use larger N&S's. STILL, all Webers are LOW-Pressure, 3 to 3.5#.
The "Filter King" filter / regulator offers MORE adjustment than the FRB 11, and is a good choice for race applications.
All this from my experience. I hope it's helpful.
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Illinois SNO Alfa Chapter Director
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