Fuel pressure problem..I'm at a loss.

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That’s a prefilter, 85 micron. Is it before the pump or after the pump before the carb? Those are the exact filters Aeromotive claims do NOT have enough surface area and cause lots of problems. Have you disassembled it and looked at the screen?
 
Hopefully these are legible.
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Pshh, I got a fuel filter for ya....
If it helps I'll send it.
...Designed for flow rates up to 90 GPH with minimal pressure drop (0.2 psi @ 45 GPH) 5 micron.....
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TT5.9mag said:
That’s a prefilter, 85 micron. Is it before the pump or after the pump before the carb? Those are the exact filters Aeromotive claims do NOT have enough surface area and cause lots of problems. Have you disassembled it and looked at the screen?
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I couldn't get the damn thing apart..lol. It is between regulator and carb.
 
TT5.9mag said:
It is possible, With the right pump. On the engine masters show Freiburger just made over 1000 hp on a BBC with a tunnel ram and two 4s naturally aspirated, all fed by a mechanical pump.
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Freidburger is great I like that show, but, pulling the snot out of an engine on a dyno is not even close to getting it to work on the road.
 
pishta said:
@512Stroker Im in the group that says a turret style mechanical can feed a 512. Let me back it up with this:

View attachment 1715768348

This data is for a 325 HP 340 but even if you double the horsepower to a very hot 512's potential 650HP all 3 besides the Holley 80 are still capable of feeding that per that graph..and he's losing the fuel pressure at a few seconds out of WOT. Wish we could see if the pump rod is seizing up after a WOT run, then any mechanical pump you run is going to go to zero. Maybe worth a shot to remove the pump rod and check it for galling or run a crocus cloth over it to knock down any high spots? I think the OP may need to get a remote gauge and monitor when the pressure really starts to drop. The pumps are proportional to engine RPM to a point but by design, they top out at the prescribed PSI or close to it under no load conditions.
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Nice graph, I agree it all looks good on paper. Now let me see it work in the car not in an Engineering lab that gathers data for the Marketing department.
 
If your line vapor lock is happening after a WOT, its getting heat soak from a header/exhaust pipe. Shield or wrap the fuel line prior to the pump. If you use the corvette vented fuel filter and your return line, it can't vapor lock up there (past pump) as the (boiling fuel) pressure is going to be vented to the tank via the 1/4 return line (and possible overcome that 9.5 psi issue) . If the fuel is boiling in the supply line it will expand and force itself out the tank end as there is less resistance in that direction. then youll have a dry line, no pump output pressure and carb bowls that are empty. Worth a shot to shield or wrap those fuel lines where they pass a hot surface if not already shielded.
 
512Stroker said:
Very nice I like it.
I will still stand by my statement
An open hood drag car is still a long way from what the OP is trying to do.
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I tend to agree with you. For this (mechanical pump and big hp) all things need to be absolutely perfect.
 
pishta said:
If your line vapor lock is happening after a WOT, its getting heat soak from a header/exhaust pipe. Shield or wrap the fuel line prior to the pump. If you use the corvette vented fuel filter and your return line, it can't vapor lock up there (past pump) as the (boiling fuel) pressure is going to be vented to the tank via the 1/4 return line (and possible overcome that 9.5 psi issue) . If the fuel is boiling in the supply line it will expand and force itself out the tank end as there is less resistance in that direction. then youll have a dry line, no pump output pressure and carb bowls that are empty. Worth a shot to shield or wrap those fuel lines where they pass a hot surface if not already shielded.
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Excellent points. I’m wondering if there is vacuum (lots) from restriction on the inlet will anything help, after the fact.
 
the bypass fuel filter will also cycle the fuel in the supply lines to prevent the lines from getting hot enough to vaporize the fuel. They will be (always flowing) liquid cooled. The space shuttle rocket motors used something similiar, used the super cooled fuel to cool the nozzles by pumping it through the nozzle walls prior to burning it. They factored in a few of the lines bursting (eg. 28) and on one mission they counted 26 lines failed on the post flight check. If 28 burst the sensors would have picked up a dip in fuel pressure and that engine would have shut itself down and most likely would have aborted that mission.
 
pishta said:
the bypass fuel filter will also cycle the fuel in the supply lines to prevent the lines from getting hot enough to vaporize the fuel. They will be (always flowing) liquid cooled. The space shuttle rocket motors used something similiar, used the super cooled fuel to cool the nozzles by pumping it through the nozzle walls prior to burning it. They factored in a few of the lines bursting (eg. 28) and on one mission they counted 26 lines failed on the post flight check. If 28 burst the sensors would have picked up a dip in fuel pressure and that engine would have shut itself down and most likely would have aborted that mission.
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This is why I'm going to a regulator with a return side on it. The regulator will be here Wednesday and we shall see if that solves it or, if an electric fuel pump is in my future..
 
Does it do it worse in any particular gear?
ie is it related to how much time you spend at WOT in a particular gear? and thus to how much heat is being generated.
Or is it strictly related to, after the engine has returned to idle/near idle, after that 1/8th mile of slowing down... assuming while still in gear?

The reason I ask is because I have seen this;

Slowing down for an extended period of time with the throttles closed, will cause a lean situation. If the Transfer-slots are also shut off, then very lean.
So the rear wheels are driving the engine lean, but the rpm is still high. So the fuel-pump is still working overtime, dead-headed.
While this is going on, the sparkplugs are getting hotter every second, because of the high-rpm, low gas situation. Finally, arriving at an rpm that you want to cruise at, you open the throttles; which starts up the low-rpm circuit and maybe the mains. When the cold gas hits the hot plugs, anything can happen.
Of course the pump is still deadheading.
IMO,
if the line from the pump to the carb is under pressure, it is impossible to vapor lock. But if the pump has been sucking the tiniest bit of air this whole time, with the float valves mostly closed on the closed-throttle shut-down, that air is now past the pump, and the pump has lost it's prime.
I had this happen to me years and years ago, on a mostly stock system.
And what I found was that the rubber jumper from the sender to the hard line was not sealing. Since it is at the highest point, it did not leak at shutdown. Since it was a tiny leak, the carb seemed to have enough fuel most of the time. And since I'm a streeter and never on the gas for more than say 5/6 seconds atta crack, I never noticed any of this. But the first time I ran 14 seconds at WOT, pow! I had trouble.
Now, I'm the guy who put that new jumper on there, with two correctly sized gear clamps. So I installed two more, total two per side,and rotated them so that the screw heads were 180* from eachother.
Badaboom no more trouble.
Don't know if it applies or helps but I thought it was worth mentioning.
 
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I ditched the mechanical pump for an Aeromotive stealth tank with a 340LPH pump. It required a return style regulator setup with my particular fuel system. They make A, B and E body tanks.

We made the spacer for the tank to help with any vibration. It wasn't 100% necessary.

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512Stroker said:
Wow you went all out!
3 regulators or am I seeing triple vison.
Does it work?
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There is a regulator for the carb, one for the nitrous and the one on the end sets the return pressure. The in tank pump operates at EFI pressures and therefore must be regulated way down for a carbureted application.
 
Jeremiah said:
There is a regulator for the carb, one for the nitrous and the one on the end sets the return pressure. The in tank pump operates at EFI pressures and therefore must be regulated way down for a carbureted application.
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Did it solve your problem?
 
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