Hey guys, I upgraded to a stroked 512 last summer and now I'm looking to upgrade the fuel line with PTFE braided stainless. Factory lines are 5/16" supply with a 3/16" return. Motor is pretty docile with having untouched Eddie heads and a 239 @ .050" roller cam in it. Future plans include pulling the heads off for CNC porting and a 600HP FiTech - won't be going beyond that, so room for upgrades beyond this level would be unneeded.

I was thinking 3/8" supply and 1/4" return. Opinions? Thanks guys!

I'm not near your power level, but when I added the 600hp Fitech, added a 3/8" line for fuel and used the factory 5/16" for the return.

That way you're only adding 1 line.

When I build a return system I usually use the original supply as the return and upsize the new supply. So I'd got with the 3/8" supply and use the existing 5/16" as a return. You really can't go too big on the return, within reason in case some clown want's to mwntion 2" black pipe or some such silliness.

I would absolutely not use 1/4" retuirn. If you use 3/8 feed use the same for the return. Absolutely would make the return at least 5/16.

I am building a 69 GTX with a 505 about 700 hp. I am running 8 AN (1/2") feed and return. Aeromotive tech support agreed with these sizes.

If using a high flow,volume electric pump I would use a 3/8 supply,3/8 return, that is how my car is, 5/16 is ok for EFI, because it runs a much higher pressure, but for a carb,3/8 would be better for a return, mine is carb for now.

I personally like the idea of using the stock 5/16" line as a fuel return. It's already there, well-routed & simple.

On my 496 I run 3/8" supply and 5/16" return. It is EFI. Works fine. Carb style regulators may like a bigger return. IDK.

For what it is worth, I like and run stock style steel lines (mostly). Tough, cost effective and they route well in the rear which can be tough. I use braided racing hose at the ends to hook everything up.

I should have stated that I plan on using an in-tank pump like the Aeromotive 340 when I change over. I'm just not a fan of the under hood surge tank FiTech sells. It'll be a another season though before that happens. Just trying to get the lines in order this year.

Thanks for the input everyone. This forum has been invaluable to me over the years.

I have the 600 HP FItech, and an in tank pump, and use 3/8th line for both feed and return. The large return line seems to help keep fuel temps lower.

The 5/16 and 1/4 lines are a no go.

I have exact set-up, 600 HP Fitech with Spectra tank with in tank pump.
Added 3/8" line for feed and used existing 5/16" for return. Works perfectly.

Curious why you say it's "no go"?

Nice thing about Fitech is you can adjust the voltage to the fuel pump , PWM, to lower the fuel pressure if needed.

I'm sorry, I meant the specific combination of 5/16 feed and 1/4 return line is a no go. That would overheat and kill the fuel pump very quickly.

Here's a helpful article where Aeromotive recommends certain line sizes for different horsepower engines.

http://www.stangtv.com/features/fuel-system-troubleshooting-killing-gremlins-with-aeromotive/