Fuel pressure

This is a little off topic for this group but.... I just finished building an experimental plane powered by a 347 all aluminum small block Ford. I am running a holley red pump upstream of my mechanical carter pump feeding a Holley 500 cfm two barrel. At idle my fuel pressure while using just the mech pump is just right at 5 psi, On take off with the engine at full power the pressure drops to .5 psi. When I switch on the electric pump it goes back to 5 psi. The question for you guys is.... Has anyone out there run a Holley red pump up stream of your mechanical pump and did the fuel pressure drop because the electric couldn't pass fuel when it is off????. There is a few pics of the plane and engine at CH701.com. Maybe one of you can see something that I have overlooked. Look for builders pics and then click on Ben Haas. Thanks in advance for any info on topic..

Ben Haas

Reply to
Ben Haas
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The electric pump needs to be running or it creates an obstruction in the line. The mechanical pump just can't pump enough fuel to spin the vanes. If you're going to run the mechanical all the time and the electric pump some of the time, there needs to be two seperate fuel paths for each pump. Put a Y just before the carb, and a one way valve in each line to keep fuel flowing in the right direction. Just curious - since I know almost nothing about aircraft engine design - is there a fuel starvation problem while banking? Some off roaders have problems with off camber driving exposing the fuel jest to air. And what about negative G loads? Won't that spill fuel out the vents?

Reply to
.boB

In a bank the G's are posative so all the fuel in the tanks and carb and also the oil stays in the pan just like the plane is sitting on a flat surface. Now if you want to do aerobatics it takes a fancier fuel set up and a dry sump oiling system. Thanks for the input,I will be running a seperate path around the electric pump with a check valve so when the holley pump is off the mechanical one can draw fuel ok.

Reply to
Ben Haas

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