-8AN fuel feed too large?

[BIG. T]

I bought a racetronix sending unit with a walbro 255LPH installed. It has a -8AN feed line and a -6AN return line. -8AN fittings are welded/brazed onto the sending unit.

I already have -8AN fittings at the fuel rail, -8AN hoses + various other -8AN straight fittings needed etc. Along with the fittings needed for the vette fuel filter/regulator. Planned on purchasing 1/2in SS line to run along the frame rail and use two Swagelok compression -8AN fittings on the ends so I can connection the hose.

I'm worried about pressure drop maybe? From the larger line?

Or should I repurchase everything and buy all -6AN fittings, hose, and SS hard line for the frame rail?

 

[TTLSX418]

I have a Fast fuel system on my wagon, it has a -12an line from the cell to the pre-filter/pump/post-filter assembly, and then a -10an line from the pump assembly to the regulator. I don't seem a problem with having a return line that is 1 size smaller than the feed line. I'd almost prefer that, remember not all the fuel is gonna be returned to the tank, just what wasn't used.

With the price of -an fittings, who really wants to replace all that?

 

[79loserbluebu]

You will be fine with -8 all the way up. To be honest though, I believe the regulators inlet and outlet are either 3/8 or 5/16 which I believe is the same size as -6

 

[BIG. T]

Yea the outlet on the vette fuel filter/regulator is 3/8" only I believe.

Planned on using this, I can't seem to find -6an female to -8an male fitting (doubt it exists) so I bought a aluminum -8an weld fitting to weld onto this. This 3/8in fitting would be the smallest line in the feed system.

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[10secBu]

I don't seem a problem with having a return line that is 1 size smaller than the feed line. I'd almost prefer that, remember not all the fuel is gonna be returned to the tank, just what wasn't used.

Maybe at WOT, but at idle most of the fuel is bypassing.

I ran into this with my carb setup when I built my car 20+ years ago. I had #10 feed and #8 return. Could not set the regulator pressure down as fuel was backing up in the return line at idle. Had to swap the return line out for #10 ($150-200) and the pressure was able to be adjusted down to where it should be.

Maybe fuel injection systems are different...

 

[TTLSX418]

Maybe fuel injection systems are different...

I'd agree with you there, 7psi on a carb vs 35+psi on an EFI set-up will require different set-ups. My injectors are 150gph injectors, so i'll need constant pressure at high boost.

 

[Doober]

The stock size on TBI is 3/8" feed, 5/16" return, pressures are around 12-15psi. I'm running a Vortec replacement pump in the 18-23psi range with a vacuum reference regulator on a Vortec 383 and I'm pretty sure I don't have any issues, stock Vortec pump is rated at 60psi. If I remember right, 3/8" (-6AN I believe) is enough for the 500hp range.

Adding a link with some info.

Switching to Powerjection III

www.ffcars.com

 

[79loserbluebu]

Hope it's not too late!
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