Fuel pump questions (big block street car)

[DeezNutz]

For a quiet equivalent to a Holley blue I use a Mallory 110. The best option for you in my opinion.

[77cruiser]

Would you be able to use a in tank pump?

[GRTfast]

Would you be able to use a in tank pump?

I “could” do anything, but that would be a lot of work to solve something that isn’t really a problem. If I went that far the car would get fuel injection.

[gnicholson]

The best pump to use is a factory fuel injection style in tank pump for reliability and best performance whether you use something from Aeromotive or a factory style pump you'll need the right bypass regulator but once you get it set up they just don't cause problems and you eliminate a lot of problems from external mounted pumps inherent to the design and the fact they have to pull fuel rather than push it. You'll have to either modify your tank and equip it with the proper baffling or just buy one from one of the companies out there designed for an in-tank pump already and your set

[tenxal]

I could always leave my electric pump in place with some plugs in it. It is on the frame right there by where the mechanical pump mounts to the engine.

Big red flag, here. Electric pumps are good 'pushers' but not so good at 'pulling'. Mount in back by the tank...preferably behind and lower than the tank outlet.

[GRTfast]

Big red flag, here. Electric pumps are good 'pushers' but not so good at 'pulling'. Mount in back by the tank...preferably behind and lower than the tank outlet.

I appreciate you concern, however it has worked great for 15 thousand miles or so. I think the reason is because my tank is mounted about 2 feet higher than the pump. Accordingly, there is a good amount of pressure at the pump inlet. The pump doesn't care about where it is, only the pressure at the inlet. I have never had a fuel starvation issue. This thread is about coming up with a more reliable and quiet arrangement.

[GRTfast]

Got the new configuration installed. Edelbrock 110 GPH mechanical pump with a "seals it" heat isolation gasket system. Composite pushrod. I have a T after the fuel log with a 0.040" orifice feeding the return line. I damaged my fuel pressure gauge when I was swapping all the fittings from the old bypass regulator to the new T, so I am waiting for that to come it.

I calculate that I should get about 0.16 liters per minute going back down the return line (based on 8psi and the return jet size). The fuel line feels kinda hot from the pump to the carb (braided stainless -AN line), I wonder if that is enough flow to keep it cool enough to prevent boiling in the line or at the pump?

Once I get the fuel pressure gauge installed I am going to play with larger orifices in the return jet. I want the biggest one I can get without starving the engine for fuel. I suspect that high volume pump can accommodate a larger return jet than 0.040".

All that said, I went on a long drive yesterday with some traffic and some long on throttle pulls, everything seems to work well. Nice not to have the electric pump whirring away all the time.

[BobbyB]

Got the new configuration installed. Edelbrock 110 GPH mechanical pump with a "seals it" heat isolation gasket system. Composite pushrod. I have a T after the fuel log with a 0.040" orifice feeding the return line. I damaged my fuel pressure gauge when I was swapping all the fittings from the old bypass regulator to the new T, so I am waiting for that to come it.

I calculate that I should get about 0.16 liters per minute going back down the return line (based on 8psi and the return jet size). The fuel line feels kinda hot from the pump to the carb (braided stainless -AN line), I wonder if that is enough flow to keep it cool enough to prevent boiling in the line or at the pump?

Once I get the fuel pressure gauge installed I am going to play with larger orifices in the return jet. I want the biggest one I can get without starving the engine for fuel. I suspect that high volume pump can accommodate a larger return jet than 0.040".

All that said, I went on a long drive yesterday with some traffic and some long on throttle pulls, everything seems to work well. Nice not to have the electric pump whirring away all the time.

I don't think there is any way to know without just testing it. Just be sure to watch fuel pressure at WOT so you do lean out your engine.

You said before your carb stayed cool to the touch with the electric pump. How did the carb temp seem with the new set up?

[GRTfast]

Got the new configuration installed. Edelbrock 110 GPH mechanical pump with a "seals it" heat isolation gasket system. Composite pushrod. I have a T after the fuel log with a 0.040" orifice feeding the return line. I damaged my fuel pressure gauge when I was swapping all the fittings from the old bypass regulator to the new T, so I am waiting for that to come it.

I calculate that I should get about 0.16 liters per minute going back down the return line (based on 8psi and the return jet size). The fuel line feels kinda hot from the pump to the carb (braided stainless -AN line), I wonder if that is enough flow to keep it cool enough to prevent boiling in the line or at the pump?

Once I get the fuel pressure gauge installed I am going to play with larger orifices in the return jet. I want the biggest one I can get without starving the engine for fuel. I suspect that high volume pump can accommodate a larger return jet than 0.040".

All that said, I went on a long drive yesterday with some traffic and some long on throttle pulls, everything seems to work well. Nice not to have the electric pump whirring away all the time.

I don't think there is any way to know without just testing it. Just be sure to watch fuel pressure at WOT so you do lean out your engine.

You said before your carb stayed cool to the touch with the electric pump. How did the carb temp seem with the new set up?

bowls were warm, but not hot. definitely a good bit hotter than with the electric pump, but that pump output 15 psi, and I had the regulator set to 6 psi, so it was pumping fuel back to the tank like mad. As long as this setup will keep it from boiling on hot florida days in traffic, I will be happy.

[GRTfast]

Once I get the fuel pressure gauge installed I am going to play with larger orifices in the return jet. I want the biggest one I can get without starving the engine for fuel. I suspect that high volume pump can accommodate a larger return jet than 0.040".

I don't think there is any way to know without just testing it. Just be sure to watch fuel pressure at WOT so you do lean out your engine.

If I can find a pressure vs flow chart for this pump, I can calculate it. I can't seem to find that information though. The pump is the 110 GPH pump that edelbrock makes for summit. rated at 8 psi.

The fuel demand for my engine is any easy calculation. If I had that chart, I could see how much additional fuel the pump could provide at say 6 psi (what I was running my electric pump at), then calculate the return orifice size that would give me enough flow to sum to that pump capacity. Then I would back it down a little for some safety factor.

[rp930]

I think the .040 will be fine. A lot of guys use .032 not sure why but seems to work.

[GRTfast]

I think the .040 will be fine. A lot of guys use .032 not sure why but seems to work.

Yeah, i just found a chart that shows the flow rate of a holley 110 gph mechanical fuel pump, it is around 60 gph in the TQ and HP peak zone of the engine.

My engine is in the 530 hp range, so the fuel demand at WOT is around 45 GPH, so I should theoretically have 15 or so GPH to spare.

I used on online flow calculator (easy) to see how much flow a 0.040" orifice is at 6 psi and it is around 4.4 GPH or so. A orifice size of 0.060" is about 10 GPH. I think that is probably approaching the limit. I'll roll with the 0.040: for a while and see how it performs in hot traffic.

[GRTfast]

I think the .040 will be fine. A lot of guys use .032 not sure why but seems to work.

Yeah, i just found a chart that shows the flow rate of a holley 110 gph mechanical fuel pump, it is around 60 gph in the TQ and HP peak zone of the engine.

My engine is in the 530 hp range, so the fuel demand at WOT is around 45 GPH, so I should theoretically have 15 or so GPH to spare.

I used on online flow calculator (easy) to see how much flow a 0.040" orifice is at 6 psi and it is around 4.4 GPH or so. A orifice size of 0.060" is about 10 GPH. I think that is probably approaching the limit. I'll roll with the 0.040: for a while and see how it performs in hot traffic.

So, curiosity got the better of me. Decided to trust my calculations and move up to a 0.055 hole in the return jet. Car pulled to 120mph or so (closed course, ) with afr at 12.5:1 rock solid. Came home and let it idle for about 15 minutes. Fuel line was pretty cool as was the carb. I think that is the sweet spot.