460 Ford Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter · #1 ·
Hello,

The 521 is ready to go back in the car. Im converting to an electric fuel pump and probably going with the Holley blue pump, but with a return style regulator to not overheat it. On top of the engine sits an ultra double pumper 850cfm.

Holley recommended a dual feed kit, but it's only -6AN. As the engine makes about 500-525 hp, is -6AN adequate to run from carb all the way to the tank?

The stock fuel line is also still there in the Lincoln, which is 3/8. Is that adequate for this engine?

Thanks
 

·
Registered
Joined
·
887 Posts
If you never plan on making any changes or upping the power level a -6AN should keep the engine fed. If it were me I would run a -8AN feed and use the stock 3/8” line for the return. How are you pulling fuel from the tank? Are you using a stock sending unit?
 

·
Registered
Joined
·
88 Posts
Your diameter concern is only in the reduced pressure section from the regulator to the carb, and 3/8" will work there. From the pump to the regulator is higher pressure, so 3/8" is plenty for that run. As a more extreme example, this is why an EFI 5/16" line can feed double your flow at 6x the pressure your carb uses. More pressure = more flow in the same size line. Caution should be taken that many pumps (not all, such as the Holley Blue) are rated at 0psi (zero) pressure. Pump flow capacity will reduce as pressure increases.

Geek food follows. Skip this if you only want the answer, without the why:
If I want to prove this, in my car with my parts, fittings, filters, advertised numbers and all, I test the regulator return flow. The return flow is the unused excess fuel that is available for use at the regulator's set pressure. Yes, you can monitor your fuel pressure at max demand, but that's difficult for most. If you can, great, and more data means more confidence that you have no issues or can spot them before something ugly happens. This test finds issues before you leave the shop.

Don't do this - this is how I do it and you don't want to do something stupid like me. I run the return to a suitable container using fire precautions, and time the return flow for a specific period. Let's say I get 32 ounces (1 quart) in 15 seconds. In one minute, that's a gallon. In one hour, that's 60 gallons, or 60 gph. Is that enough? Let's see:
HP x BSFC ÷ Pounds per Gallon x restrictive flow compensation = Required flow in Gallons Per Hour
For 525hp, at a typical BSFC of 0.5 pounds per hour, would need:
525 * 0.5 / 6.2 * 1.2 = 51 gph

OK, so let's break that down. BSFC is brake specific fuel consumption in pounds, or how much fuel is needed to make 1hp for 1 hour. Look-up typical values for your engine or from your dyno sheets, but they can range from roughly 0.4 to 0.6 pounds per hour, and most of our engines are around 0.5 at peak power on gasoline. So, 525 x 0.5 = 262.5 pph required.

Another caution, if you are running a low-energy fuel like E85 that needs a lot more volume for the same power, you need to change the BSFC and weight for that fuel. You may also require larger lines to feed that volume, so do your homework.

A gallon of non-ethanol gasoline is about 6.2 pounds. So 262.5 pounds divided by 6.2 per gallon is 42.3 gph. That's actually what the engine needs for 525 actual hp. So, what's the 1.2? In order to have a real-world buffer to compensate for low-voltage, dirty fuel filters, long-term fuel pump wear, etc, we add 20% extra to cover for stuff like that. Insurance. Some simpler calculations don't have this specified buffer, and instead use lower fuel weight or other skewed number to get the same effect with a simpler formula.

42.3 x 1.2 = 51 gph. We have 60 gph return flow that exceeds our 51gph requirement, so we have the flow to feed 525 hp, at required pressure, with buffer, and still plenty to spare. 😁 We also easily have enough to run common pump gas E10 and similar. I hope that helps in both sizing your fuel pump and lines, and how you can do more than guess and buy oversized stuff to be sure, and still wonder if it's enough.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #6 ·
If you never plan on making any changes or upping the power level a -6AN should keep the engine fed. If it were me I would run a -8AN feed and use the stock 3/8” line for the return. How are you pulling fuel from the tank? Are you using a stock sending unit?
Thanks, going with -8an, just to be sure. I was thinking I could probably use the stock 3/8 line and sending unit as a return from the regulator. This way I still have the fuel sensor in my stock tank. Saves some money on new lines too. Then use a bulkhead fitting in -8AN as a new feed, so the pump is gravity fed.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #7 ·
Your diameter concern is only in the reduced pressure section from the regulator to the carb, and 3/8" will work there. From the pump to the regulator is higher pressure, so 3/8" is plenty for that run. As a more extreme example, this is why an EFI 5/16" line can feed double your flow at 6x the pressure your carb uses. More pressure = more flow in the same size line. Caution should be taken that many pumps (not all, such as the Holley Blue) are rated at 0psi (zero) pressure. Pump flow capacity will reduce as pressure increases.

Geek food follows. Skip this if you only want the answer, without the why:
If I want to prove this, in my car with my parts, fittings, filters, advertised numbers and all, I test the regulator return flow. The return flow is the unused excess fuel that is available for use at the regulator's set pressure. Yes, you can monitor your fuel pressure at max demand, but that's difficult for most. If you can, great, and more data means more confidence that you have no issues or can spot them before something ugly happens. This test finds issues before you leave the shop.

Don't do this - this is how I do it and you don't want to do something stupid like me. I run the return to a suitable container using fire precautions, and time the return flow for a specific period. Let's say I get 32 ounces (1 quart) in 15 seconds. In one minute, that's a gallon. In one hour, that's 60 gallons, or 60 gph. Is that enough? Let's see:
HP x BSFC ÷ Pounds per Gallon x restrictive flow compensation = Required flow in Gallons Per Hour
For 525hp, at a typical BSFC of 0.5 pounds per hour, would need:
525 * 0.5 / 6.2 * 1.2 = 51 gph

OK, so let's break that down. BSFC is brake specific fuel consumption in pounds, or how much fuel is needed to make 1hp for 1 hour. Look-up typical values for your engine or from your dyno sheets, but they can range from roughly 0.4 to 0.6 pounds per hour, and most of our engines are around 0.5 at peak power on gasoline. So, 525 x 0.5 = 262.5 pph required.

Another caution, if you are running a low-energy fuel like E85 that needs a lot more volume for the same power, you need to change the BSFC and weight for that fuel. You may also require larger lines to feed that volume, so do your homework.

A gallon of non-ethanol gasoline is about 6.2 pounds. So 262.5 pounds divided by 6.2 per gallon is 42.3 gph. That's actually what the engine needs for 525 actual hp. So, what's the 1.2? In order to have a real-world buffer to compensate for low-voltage, dirty fuel filters, long-term fuel pump wear, etc, we add 20% extra to cover for stuff like that. Insurance. Some simpler calculations don't have this specified buffer, and instead use lower fuel weight or other skewed number to get the same effect with a simpler formula.

42.3 x 1.2 = 51 gph. We have 60 gph return flow that exceeds our 51gph requirement, so we have the flow to feed 525 hp, at required pressure, with buffer, and still plenty to spare. 😁 We also easily have enough to run common pump gas E10 and similar. I hope that helps in both sizing your fuel pump and lines, and how you can do more than guess and buy oversized stuff to be sure, and still wonder if it's enough.
Thanks for this. I'm all new to this subject so definitely some info to fall back on
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #8 ·
Holley BLUE pump.................most unreliable pump ever and a loud mofo.

It's 2022 better pump's out there.

Cheers, Bob
Alright. Thought the Blue pumps were unreliable because they are sold as deadhead pumps, which tends to overheat them when idling. What are my better alternatives? Sniper pumps any good? Or are they just the same thing. Any suggestion is very welcome. Thanks
 

·
Registered
Joined
·
621 Posts
Alright. Thought the Blue pumps were unreliable because they are sold as deadhead pumps, which tends to overheat them when idling. What are my better alternatives? Sniper pumps any good? Or are they just the same thing. Any suggestion is very welcome. Thanks
This is a good one. Not as loud as a Holley but you can hear it. Which I like, so I know it's running. #8 line to feed the pump, #6 after the pump. I use a "T" after the pump returning to the tank with a restrictor plug I threaded in the T to allow return all the time. Hole size is 1/16". Works for me.
Fuel tank pickup location is the biggest issue. Low and forward for a #8 fitting, 1/2" NPT is the best. I even put a shut off valve in mine so filter change or"anti-theft" is there.
You'll also want some type of shut off in case of wreck or what ever. I use a oil pressure switch on my engine for that. An inertia switch works well to.
 

Attachments

·
Registered
Joined
·
484 Posts
This is a good one. Not as loud as a Holley but you can hear it. Which I like, so I know it's running. #8 line to feed the pump, #6 after the pump. I use a "T" after the pump returning to the tank with a restrictor plug I threaded in the T to allow return all the time. Hole size is 1/16". Works for me.
Fuel tank pickup location is the biggest issue. Low and forward for a #8 fitting, 1/2" NPT is the best. I even put a shut off valve in mine so filter change or"anti-theft" is there.
You'll also want some type of shut off in case of wreck or what ever. I use a oil pressure switch on my engine for that. An inertia switch works well to.
Interesting....I was under the impression that the return line needed to be after the regulator to function correctly.
 

·
Registered
Joined
·
621 Posts
Interesting....I was under the impression that the return line needed to be after the regulator to function correctly.
Seen it both ways. After working on many liquid and air systems in the Navy on engines, we had a relief valve, after a regular for when the pressure exceeded a PSI that you didn't want the system to have. When usage stops or slows, pressure builds, depending on the pump. "Positive displacement" pumps have to have a relief valve, (your engine's oil pump for example). Vane types, (most fuel pumps) don't. A regulator only controls the pressure down the line from it. If you look at most fuel pressure regulators, they don't have port to bleed the pressure off to. Just inlet and outlets.
Liquid will flow to the path of least resistance. If the regulator is wide open, the fuel volumn my pump puts out, will more then keep up with the carb/engine demand, even with a bleed off. If I used a 40GPH pump, it would probably be a problem. But I use a 120GPH pump, AKA 2 gals per minute flow. With the bleed off port I have, it not only bleeds off fuel for cooling but some pressure to help the regulator do it's job. I also noticed a decrease in pump noise with it to.
 

·
Registered
Joined
·
88 Posts
+1, the regulator provides the bleed-off and return flow, so no T-restrictor is necessary. A bleed can help pump cooling flow in a deadhead system, but reduces system capacity, forcing an oversize pump to maintain the required flow. No biggie, but unnecessary with a return regulator that provides regulated pressure and constant flow for pump cooling.

A common race and motorcycle method is to reduce pumping power at low-demand. In bikes with small charging systems, this helps slow/idle battery charging, and in power vehciles it reduces power consumption and heating. Small systems have used a throttle switch to enable a power resistor at low throttle for low pump speeds, and race stuff typically uses a pump controller reading manifold pressure. More load = more MAP pressure = more pump power to feed demand. It doesn't have to be balls-out all the time, and has multiple benefits.
 
  • Like
Reactions: JimL
1 - 12 of 12 Posts
Top