Bigger Banjos

Can't help with your quest, but would like to understand your problem better. Are you saying that the upstream carbs are so thirsty that the 7/8 carb doesn't receive enough fuel or that you'd just like the volume of recirculated fuel to be larger (and you've already removed the orifice restriction at the 7/8 carb exit)?

 

You could try Speedflow. I've purchased a few of these.

http://www.speedflowshop.co.uk/145mm-eye-to--6-aluminium-double-banjo-721-06-336-p.asp​

 

These might help you out. I believe they would work with non-braided line and thread right up to the Speedflow dual banjo.


http://www.holley.com/700106ERL.asp​

 

I looked around on Google, is this banjo big enough?
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I think you may be avoiding "steel braided hose", simply to keep the appearance traditional.
However, it is magnitudes more reliable and safe than a rubber fuel line, 10% ethanol and Chinese hose clamp combo.

You can buy black hose with black/silver anodized AN fittings from XRP, which is my favorite source. In a pinch, you can use heatshrink tubing over -6 hoses, and look "period correct".



http://www.xrp.com/index.htm


JM3

 

Interesting problem, and the sketch is great, but I have a few more questions:

1. I'm used to a "regulator" being a device that keeps its output pressure constant regardless of the inlet pressure and regardless of the flow rate passing thru it. The device you show/describe seems to be something where you can adjust it to achieve a given inlet pressure when the outlet is at zero pressure and leaking at rate X. Then, as boost is applied, it becomes more restrictive, raising the inlet pressure, and reducing the outlet flow to Y while the outlet pressure is still zero -- is this a correct rough understanding?

2. You mention that if you remove the supply line from the 5/6 carb, the pressure gauge reads ~1 psi. What is the flow rate out of the supply hose in this condition?

3. I think you state that, if you remove the line from 7/8 carb that enters into the "regulator", the pressure gauge reads ~4.8 psi, Is that correct? What is the flow rate out of the hose in this condition?

4. What is the maximum fuel flow rate that you believe the engine needs?

My gut feel is just that your pump is too large, and you would be recirculating a lot of fuel needlessly. However, if the flow rates in #3 and #4 aren't very different, then you are between a rock and a hard place, and would have to do something to reduce the pressure drop in the carb banjo fittings; otherwise, each carb would be operating at fairly different inlet pressures. Anyway, if you got the time would love to more about what you're doing...

 

Had another thought that you might be better off using an architecture more like the K/KE-Jets where the fuel pump supplies the regulator directly (which recirculates a big flow back to the tank) and then the engine supply is "Teed" of the inlet to the regulator (where you would use the stock orifice at the 7/8 carb outlet and recirculate that small flow back to the tank as well). I'm out for a few hours, but will post a sketch later.

 

It's a bass banjo of course.

 

Don't know why I couldn't recognize earlier this morning that the regulator that you are using works exactly like the K/KE-Jet regulators -- i.e., the inlet pressure is held constant by varying the flow with the outlet always at ~zero pressure. Consequently, I think that you'd be a lot better off using this configuration:
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The advantage to this configuration is that only the fuel entering the engine (and the small amount leaking out the orifice) has to pass thru the banjo fittings. The problem that you are having now is being caused by having the entire flow out of the fuel pump (what the engine uses + the return flow) passing thru the banjo fittings.

The 100 gph (about 6.2 liter/min) pump might be a little on the high side. The stock K/KE-Jet delivers about 2.6 liter/min (for ~230 HP), so you should be good for ~570 HP , but I'm sure that you'll have much less of a problem using this other configuration.