Feeding a carb with an EFI fuel pump
 

I'm trying to set up my 350 c.i. Camaro with a Holley four barrel carb and an electric fuel pump. What are some good fuel pumps for this that fit in the original sending unit? Right now I'm looking at a Bosch pump 6925821 which is listed for a Camaro with 305 and 350 engines. I can't find any info on whether it's for TBI or TPI, but I'm guessing TBI. From what I'm reading online (and I know everything online is the absolute truth:) ) Bosch and Walbro fuel pumps are about the only ones worth buying any more if you want something that you want to last. Obviously, on 3rd gen F-bodies you don't want to be having to replace the fuel pump any more than you absolutely have to, and you sure don't want to get stuck somewhere out in the boondocks with a fuel pump that gives up the ghost prematurely.

I'm wondering if there is a disadvantage or an advantage to using a stock style EFI fuel pump with a fuel pressure regulator over using a low pressure fuel pump with or without a regulator. Seems like with a TBI pump, for example, the fuel pressure regulator is going to be needing to return a lot of fuel back to the tank to maintain the lower pressure the carb needs, meaning a lot of fuel is going to be constantly circulating between the tank and regulator.

Re: Feeding a carb with an EFI fuel pump
 

TPI, TBI or carb...don't they all use the same amount of fuel idling or otherwise? So the return to tank fuel would be the same amount??

Re: Feeding a carb with an EFI fuel pump
 

I think the carb would use more fuel since most carburetors aren't as efficient as fuel injection. It's the pressure each system requires that is the main difference, but I suppose the flow rates might be different as well. I just think there has to be a reason why there are different pressure (electric) fuel pumps for TBI, TPI and carburetor, and so why use a fuel pump that is designed for a higher pressure than what you need.

The only reason I can think of for using a TBI pump (and pressure regulator) for a carb conversion is because that's the lowest pressure pump you can get that fits in the 3rd gen F-body sending unit, so it's easiest to do it that way. Otherwise you have to modify the sending unit to eliminate the intank pump and retrofit an external low pressure pump somewhere close to the tank. I know there are posts on here about how people have done this. The only low pressure intank electric fuel pump I'm aware of is the Vega pump, but I suspect this might not flow enough fuel for a 350 c.i. V8.

Re: Feeding a carb with an EFI fuel pump
 

I purchased a Holley 12-879 from Summit has 2 springs. As delivered 4.5-9psi. Second spring 15-65psi Able to run carb now then change spring for use with TBI

Re: Feeding a carb with an EFI fuel pump
 

Flow rate is determined by the needs of the engine at WOT which is typically estimated by your expected max HP. Fuel pressure is another thing, and the more pressure you have, the more you're going to work the fuel pump to provide it. Obviously EFI wants to run at 40+ PSI, and carbs want 5-9 PSI, pretty big difference. You can regulate 40 PSI down to 5 or whatever, but you will need a very good (i.e. expensive) regulator to handle that sort of step down. Meanwhile, your pump is pressing hard the whole time against the regulator. If your pump was only outputting 10 PSI, that's a lot easier to regulate down to 5. It's better to pick a pump designed to flow the amount you need at the pressure you want.

Re: Feeding a carb with an EFI fuel pump
 

That's what I thought, too, which is why I made the post. I believe the TBI pumps might run at a lower pressure than the TPI ones since the TBI system itself runs at only 9-13 psi. I suppose that might be easier to regulate down to the 4-5 psi of a carb. I still wonder if a Vega pump would work since Vegas had in-tank fuel pumps and were carbureted.

Re: Feeding a carb with an EFI fuel pump
 

I have fought this beast for 15 years. I have a TBI car I swapped 350 carb into, kept the stock intank TBI pump and used the high dollar regulator. It never worked as you'd like. Fuel pressure was always irratic. Some days car left me stranded. Other days was hit or miss if it was going to drive smoothly or give me issues like it was getting too much fuel or too little fuel. Sometimes WOT would just backfire & fall flat on its face, other times would take off like a rocket - you never knew from one light to the next. I always suspected problem was in trying to reduce that much pressure.

This summer, I took the damn intank pump out, replaced with a piece of metal brake line and a sock, and installed an external electric pump under hood with a newer fuel pressure regulator. Runs smooth, like it always should have. Kicking myself for not having done this 10 years ago.

I used Edelbrock 17301 Micro Fuel Pump, and I had a new Holley 12-882 return style fuel pressure regulator laying around. Plenty of fuel to feed a 350 build (up to 400hp).

KISS - Keep It Simple Stupid! 😉

Re: Feeding a carb with an EFI fuel pump
 

Why would you put the electric fuel pump under the hood? I thought external electric fuel pumps should be placed as close to the tank as possible and below the tank because they push fuel a lot better and they pull fuel. A previous owner had done this on this car I have only it still had the fuel pump in the tank, which looks to be almost new. Since the external fuel pump that was installed by the Edelbrock carb they swapped in looks like it was an afterthought I'm wondering if they didn't have the same problem of not getting the TBI intank pump to work right with the carb.

Re: Feeding a carb with an EFI fuel pump
 

Below the fuel tank? Really? Have you looked under a 3rd gen? The only place to mount anything under the fuel tank, is in the pavement! Yeah yeah, I've read that pushing vs. pulling all over, people keep repeating the same info. I've been driving almost daily for 2 months with no issues at all. Always cranks, always runs, never any idle or WOT issues. Anyone welcome to do theirs anyway they like. I just wanted to throw out there that ... I read all that, I tried to follow suit, and I had nothing but problems. But I did it the "wrong" way, and I'm driving without issue.

Re: Feeding a carb with an EFI fuel pump
 

You could actually mount an electric pump on the brace above the panhard bar or on the left sub-frame rail before it goes to the fuel filter and it would be well below the tank (and well above the ground). I would think if you mount the pump wrong it's going to have to work harder to pump fuel and it might not last as long. The suggestions on how to mount these pumps are largely from the companies that make them so I would think the people there know what they are talking about.

Re: Feeding a carb with an EFI fuel pump
 

I'm not interested in a debate. I don't mind changing a $60 fuel pump EVERY year if it's 5 minutes under the hood opposed to 5 hours dropping the tank. I was just offering an alternative - because like yourself, 15 years ago I thought there would be some merit in the universe to me regulating an in-tank EFI pump. But after much frustration for years, I found that life is short, and I'd personally rather spend time driving. And I thought I'd simply offer another view and say "hey - it really is ok to keep it simple". It's your car, do it your way. But please don't imply that my way is wrong BEFORE you've done anything besides theorize.

Re: Feeding a carb with an EFI fuel pump
 

There certainly is no debate needed; your way is wrong because you're using a cheap junk pump that isn't actively cooled by fuel. The correct solution is to drop the tank and put an appropriate pump in the factory location.