QUOTE(ahdoman @ Apr 28 2009, 08:59 AM)
The Carter rotary is also a great pump. It's just a little noisier than the CB Rotary.
If you put in a return line I really wouldn't use a pressure regulator. It will only put the system out of balance. If you think about the "balance" of the system; Your carbs will need varying amounts of fuel depending upon how hard you are driving. A pressure regulator is a bandage. The return line allows a relief point for the extra pressure. If your car is at idle the extra fuel returns back to the tank.
If you incorporate a return line the system is usually a "loop". The idea is to keep the entire system "pressurized to the 3.5 psi. You'll need to put dual nipple banjo fitting on each carb. The send line hits the first carb, the output goes to the second carb input, that carb output goes back to the return line.
The CB pump I have is made by carter.
CB/Carter pumpBut my real question is with this "loop" return configuration.
Have you actually set this up and measured the fuel pressure being supplied
to the carbs in this configuration?
The reason that I ask is I would be concerned that without some form of
back pressure to limit/restrict the flow *after* the carbs
that there will not be consistent or sufficient pressure
maintained to the carbs to ensure proper flow into them.
Normally, what I've seen for return systems, is a back pressure regulator
with the excess pressure being returned. This type of regulator doesn't
limit flow like the simple regulators the go between the pump and carbs.
The setup you describe above has no form of back pressure other than
the smaller size of the return line and the weight of the fuel pressing down
on the returned fuel.
I'm just curious if that is enough to work even when the gas tank
is near empty.
I would think in the absences of any sort of back pressure regulator,
to keep pressure/flow consistent between the carbs,
perhaps it would be better to create a double loop with a "loop" around
the carbs that is feed and returned as part of the bigger loop
rather than a simple loop with the fuel entering and exiting each
carb in series.
See figure.
Click to view attachmentI like the simplicity.
I have no idea which if either would really work.
So my real question is still, have you ever hooked up a return
line like this and measured pressure at the carbs or actually run
a car this way to see that this method works including when the fuel
tank is near empty?
--- bill