efi pump on carb 1/2" return line - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dirtyjim · 06-19-2016, 08:51 PM

i'm getting ready to replace the entire fuel system on my 67 c10. it will be injected in the future but will still run a carb for around a year or so. the tank has rust so i'm going to a rear tank and running all new stainless hardlines 3/8 supply and 1/2" return and fragola braided nylon -6 supply and -8 return with an fittings for everything else.
i'm going to run an aeromotive 340lph stealth pump so I was wondering if anyone has used a similar setup and if the 1/2" return line was large enough to flow enough fuel back to the tank to keep from overpowering the regulator.
I have a holley 12-841 and a quick fuel 30-900 regulator on the shelf to choose from.
all I could get out of aeromotive was that the 1/2" line should be large enough but it might need 5/8 or 3/4 to flow enough back to the tank with a carb.

**kwmech** · 06-20-2016, 12:27 PM

1/2' return line should be more than enough

storm9c1 · 06-21-2016, 01:17 PM

Agreed. 1/2" should be fine, just be careful not to kink your bends and whatnot.

dirtyjim · 06-21-2016, 09:32 PM

i have imperial benders for 3/8 and 1/2 tubing and have bent quite a bit of tubing so i doubt kinking will be a problem. 1/2" stainless bends a lot nicer than 1/2" aluminum. if the 1/2" doesn't flow enough back i'll just use the 1/2" for the feed and replace the 3/8 with 5/8 and use it for the return. i have plenty of -8 and -6 hose ends and tube sleeves and nuts so i hope i can use them instead of having to go up to -10. my 37 degree flare tool will do 5/8 stainless but i don't have any 5/8 tubing on hand or -10 hose ends and fittings or a 5/8 bender.
i mostly just want the fuel system to be able to go from carb to efi with just the change of the regulator and still be able to easily support around 750 hp in the future

69chevytrucker · 06-21-2016, 10:40 PM

1/2 is plenty i switched a injected motor with 40 psi pump to a carb running 6 psi using a holley reg and 1/2 return and never had any trouble.
the reg works off the return - fuel in at say 40 and 6 psi through the reg and 34 back to the tank the reg doesnt care if there is a 100 psi in it will only allow 6 psi through when set and the rest will free flow back to the tank.

06-19-2016, 08:51 PM	#1
dirtyjim Registered User Join Date: Feb 2013 Location: alvin, texas Posts: 622	efi pump on carb 1/2" return line i'm getting ready to replace the entire fuel system on my 67 c10. it will be injected in the future but will still run a carb for around a year or so. the tank has rust so i'm going to a rear tank and running all new stainless hardlines 3/8 supply and 1/2" return and fragola braided nylon -6 supply and -8 return with an fittings for everything else. i'm going to run an aeromotive 340lph stealth pump so I was wondering if anyone has used a similar setup and if the 1/2" return line was large enough to flow enough fuel back to the tank to keep from overpowering the regulator. I have a holley 12-841 and a quick fuel 30-900 regulator on the shelf to choose from. all I could get out of aeromotive was that the 1/2" line should be large enough but it might need 5/8 or 3/4 to flow enough back to the tank with a carb. __________________ 1967 C10 lwb two tone, 305 & rat fink style floor shifted 700r4, 20" steelies 2004 2500HD utility bed aka Brutus

06-20-2016, 12:27 PM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	Re: efi pump on carb 1/2" return line 1/2' return line should be more than enough

06-21-2016, 01:17 PM	#3
storm9c1 * That's interesting * Join Date: Oct 2008 Location: Pittsburgh, PA Posts: 2,772	Re: efi pump on carb 1/2" return line Agreed. 1/2" should be fine, just be careful not to kink your bends and whatnot. __________________ Tom Chevy by day... 1969 Chevy C30 Rollback Tow Truck -- 383 stroker, 4L80E 2011 Chevy Caprice PPV 9C3 6.0L 1995 Chevy Caprice 9C1 1994 Chevy Caprice 9C1 #3 1995 Chevy Caprice Wagon #2 1995 Chevy Impala SS Mopar by night... 1969 Dodge Charger 1972 Chrysler Newport 2dr Hardtop (27K miles) Plus others...

06-21-2016, 09:32 PM	#4
dirtyjim Registered User Join Date: Feb 2013 Location: alvin, texas Posts: 622	Re: efi pump on carb 1/2" return line i have imperial benders for 3/8 and 1/2 tubing and have bent quite a bit of tubing so i doubt kinking will be a problem. 1/2" stainless bends a lot nicer than 1/2" aluminum. if the 1/2" doesn't flow enough back i'll just use the 1/2" for the feed and replace the 3/8 with 5/8 and use it for the return. i have plenty of -8 and -6 hose ends and tube sleeves and nuts so i hope i can use them instead of having to go up to -10. my 37 degree flare tool will do 5/8 stainless but i don't have any 5/8 tubing on hand or -10 hose ends and fittings or a 5/8 bender. i mostly just want the fuel system to be able to go from carb to efi with just the change of the regulator and still be able to easily support around 750 hp in the future __________________ 1967 C10 lwb two tone, 305 & rat fink style floor shifted 700r4, 20" steelies 2004 2500HD utility bed aka Brutus

06-21-2016, 10:40 PM	#5
69chevytrucker Registered User Join Date: Apr 2014 Location: calgary alberta Posts: 1,248	Re: efi pump on carb 1/2" return line 1/2 is plenty i switched a injected motor with 40 psi pump to a carb running 6 psi using a holley reg and 1/2 return and never had any trouble. the reg works off the return - fuel in at say 40 and 6 psi through the reg and 34 back to the tank the reg doesnt care if there is a 100 psi in it will only allow 6 psi through when set and the rest will free flow back to the tank.



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