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Fuel line routing - electric - bypass to tank or filter head?

Old 04-03-2021, 07:49 AM
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Originally Posted by outonsafari View Post
https://www.cpperformance.com/p-7398...ater-pump.aspx

ouch 600 bucks a piece, i was wondering why your using electric pumps to carbs when you prefer mechanical.
Yes! Even used they’re expensive. Also, I don’t have the room at the water pump to have a fuel pump there. I would have to convert the entire accessory drive and my engine harnesses to make it work. Hence electric pumps.
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Old 04-03-2021, 07:52 AM
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Originally Posted by Cap'm Kurt View Post
Routing back to the tank should work but last resort. First try preventing heat from the motor from getting to the fuel line simply by insulating the line and this may solve the problem and not have to run it back to the tank. Worked on my boat that had severe vapor lock.

But i also found that the fuel line was running close to the bottom of the oil pan. So i just insulated the line and also put a small sheet between pan and line. All vapor lock issues gone, no return needed. Easy to try. Alum bubble wrap at Lowes.
I read about how you solved your vapor lock issues. Nice job fixing it.

I have never had any vapor lock issues with the cool fuel set-up on mine. If I thought the injection pump would feed my power, I’d convert it to make it work.
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Old 04-03-2021, 08:22 AM
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Eddie Young tapped my (Gen 2 cool fuel) fuel rail and returned to tank
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Old 04-04-2021, 08:46 PM
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Originally Posted by TomZ View Post
If I thought the injection pump would feed my power, I’d convert it to make it work.
Regulate it down to 6lbs and dump in a 5 gallon jug for exactly 1 minute. See how much you pumped and x by 60 minutes.

Or, just don't regulate it and dump into 5 gallon jug. If it doesn't pump enough at free flow then no need to check at 6psi.

Engine doesn't have to run for results. Just have a good 12-14 volts available to the pump.
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Old 04-07-2021, 09:34 AM
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I have the same setup at 60 psi for EFI, however I used the cool fuel setup from a 7.4MPI with the regulator removed, and that port capped with a plate. So fuel goes from tank to filter/separator head, to the pump/cool fuel setup, to regulator then injectors, regulator return goes back to filter/separator head. It works.

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Old 04-07-2021, 09:55 AM
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How much power is it supporting? Factory pump?
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Old 04-07-2021, 10:22 AM
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Originally Posted by SB View Post
Regulate it down to 6lbs and dump in a 5 gallon jug for exactly 1 minute. See how much you pumped and x by 60 minutes.

Or, just don't regulate it and dump into 5 gallon jug. If it doesn't pump enough at free flow then no need to check at 6psi.

Engine doesn't have to run for results. Just have a good 12-14 volts available to the pump.
Furthermore, gasoline weighs about 6.1 pounds per gallon. On average, an in-tune four-stroke gasoline engine will burn about 0.50 pounds of fuel per hour for each unit of horsepower.

500hp X .5lbs = 250lbs per hr
250lbs / 6.1 lbs per gall = 41 gph

Real world with some safety, min 50gph fuel system should be safe
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Old 04-07-2021, 10:33 AM
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I should be right around the 600 mark so 50gph is right at the minimum. If the pump can flow between 60 and 70, I think that would be safe enough. If I'm recalling correctly, I think Smitty was working on a 502 that was up into the 600's and the pump was on the edge. Increasing voltage helped. This was in injected form though and the pressure requirements are a lot different. More math than I want to really get into. We'll test the pumps this weekend to see what they can do.
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Old 04-07-2021, 10:43 AM
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Originally Posted by TomZ View Post
How much power is it supporting? Factory pump?
Roughly 450-500 at the moment. Stock 7.4MPI pump. It is at least enough for 316 lb/hr (50gph) which is what I have seen at WOT.
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Old 04-07-2021, 10:47 PM
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We looked at the MPI set-up tonight and after doing the math as well as trying to figure out other options for fuel cooling and such, it was decided that the Holley pumps with bypass regulators dumping back to the tanks are the best option.

I will use the brackets that the cool fuel assembly used to mount the pumps since they put the pumps in a really good position for packaging. The inlet/outlet of the pumps will end up being roughly five inches below crankshaft centerline and about foot or so below the filter head. This position worked with no issues supplying fuel to the MPi set-up so feeding the carb should be no problem. And the bypass regulator should keep vapor lock and pump failure in check. It will also allow me to package everything at the engine so wiring and all should be easy.

The only rub will be pump servicing (odd bank header removal required), but I had that issue already. The Holley pump will be less complicated so easier to remove if I have to so that’s a plus.

Thanks for all the feedback and guidance! Much appreciated.
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