Hello, I'm designing the fuel system for my SBC powered street-able '54 Ford g***er build and have a question about mechanical fuel pump free flow rate (GPH). I'm running 8-AN line from tank to primary filter to fuel pump. I'm running 6-AN line from pump to secondary filter to high quality 'Aeromotive' byp*** style pressure regulator to fuel log feeding Carter 625 AFB dual quad's. I will be regulating the pressure down to 4.5-5.0 psi but the only pump I have found with correctly sized inlet/outlet ports is 170 GPH. I was hoping to find a 110 gph but no luck so far. QUESTION: Is 170 gph too aggressive for this naturally aspirated application? Thanks in advance for any help you can provide.
A. How many HP are you expecting to feed ? There are many charts that will tell you GPH to feed your monster . 1/2" line on a naturally aspirated SBC is overkill IMO !
How difficult would it be to run -8 to the regulator? I have a sort of similar setup on Plan II, with -8 line and 1/2" OD aluminum hard line before and after the pump to the regulator, and -6 from regulator to carbs.
For now I'm installing a 305 with hydraulic lifters, upgraded heads to support a high lift cam, high rise intake & uncorked fender well headers so if I get close to 300hp I'll be lucky. I'll look for GPH vs. HP data you mentioned. Thanks
Not difficult at all since the fuel tank is the only component of the fuel system installed and engine is still being readied for install. I'll give -8 to the regulator a look since you've had luck with that configuration. Thanks
You could easily get by with a factory mechanical fuel pump for almost any SBC and never have issues with fuel starvation. Even with twin carbs it wont ever use 110 gph let alone 170gph. Supplying it with the 6AN line you're planning will be plenty for a SBC with twin 4 barrel carbs. If you went to a stroker engine, and supercharger you might want more, but not otherwise. I'm running a 355 SBC full roller motor, with Dart SHP aluminum heads, and a very large Howards roller cam, and feeding a stock mechanical pump with 3/8" hard line. About 430 hp, and 419 torque, and this setup is plenty.
Op yr overkilling the fuel system , In one of your post Building a G***er , @ lest to me was going to be 7,500 -9,k revving SBC , Really a 300 hp can be feed with a 5/16 fuel supply normal use mechanical oem V8 fuel pump
300 HP static with 30 GPH , under full throttle add 10-15%. AT THE CARBURETOR A 450 HP 454 used a mechanical pump & 3/8" fuel line , tank to carb . Same for all the 450 HP incarnations @ GM , don't recall fuel starvation as a problem Think the BB Fords & Chrysler's used the same .
Outstanding feedback gent's and I can't thank you enough for helping me too correct mistakes before I make them. According to the AN chart I stumbled upon -6 has an ID of 3/8 which is consistent with all rubber fuel line I've used for decades so it certainly makes sense to follow in this direction. With your help I've decided to string -6 from tank to return bung and abort the -8 idea to the regulator. I will also continue my search for a mechanical pump ~110 gph which will accommodate -6 fittings. Gotta love the HAMB
You are way overestimating your fuel needs. Better too much than not enough, I get that, but I’ve got a 64 Corvette vintage road race coupe with a Hendricks 680 HP SBC that only runs a 105 GPH fuel pump. And it never, ever starves for fuel. -8 to regulator, -6 to carb and return.
The larger size of line won't hurt anything, it's better to have fuel at the ready than not enough and a decent regulator will tame the 170 down so as not to over fuel the carbs. I do run a stock mechanical pump to feed a pair of 600 cfm Carters on a hot 355 without a regulator with 3/8's line.
This is a 80 gph and you can get 1/4 npt to -8 fittings https://www.summitracing.com/parts/...78jG7o40a20DRyzezydD2_4EsasnTA3RoCpmMQAvD_BwE
Thanks for the inputs. Are any of you (-8 to regulator) guy's running a stock tank and if so how did you get -8 plumbed to the tank? Haven't dropped my tank yet so whether I go back to the -8 inlet idea or go with -6 I'm concerned about this aspect once I get into it.
Yes with a 6-8-10 , bun in bottom of tank , gravity & weight of fuel to supply fuel pump , then pump pushes , Not in your situation , a car / Vehicle can latch so hard (negative G Force ) Can cause feed problem, pulling fuel away from pump , this in 1 of reasons tanks up front using N G force to feed pump
It doesn’t matter what size -6 is advertised. A -6 fitting ID is .292” and OD is .344” …… numbers don’t lie a -6 fitting inside diameter is less than .312” which is 5/16”. Believe what you want but a -8 fittings ID is .375” which is 3/8”. It isn’t the hose……it’s the fittings that restrict flow. Barb style may measure different but remember the 3/8” hose must go over the fitting.
I use electric pusher pumps on the more performance oriented cars, one has -8 to regulator and one is -10, I've also used 1/2 inch aluminum line to regulator, -6 from regulator to carb on the -8 setup and -8 to carb on the -10 setup. What type outlet is on your fuel cell/tank now ?
Never mic'd ID of a AN fitting since I just received my first one today but .292 is less than I expected on the inlet side. I wanted to stay close to conventional fuel delivery methodology of 3/8" ID so I think -8 to the regulator is perhaps the better choice with -6 aft of regulator.[/QUOTE]
The dash number refer's to the HOSE I.D., so it stands to reason that the fitting's will be smaller. -6 is still bigger than 5/16" by the time you figure the fitting restriction. Since we're looking for volume, -6 is still bigger all the way around than 5/16" hard tube. Would -8 be better, Most certainly it would. You can never have too much supply.
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