The answer to this is it depends how much your tring to return through it........once the volume needed to return is more then the 1/4" line can handle it becomes a restriction and then pressure control becomes an issue .......but to that point it's fine. On the 90 ss truck we built a 650hp 509 bbc for I ran an aeromotive 340 on the stk pick up sender.......pump fit right on. Used the stk line and a return regulator.......the factory feed line was 3/8 and the return was 1/4.......we could keep the pressure at 7...........in stalled a 3/8 return and no issues. The tank was already setup for pump in take as it was an tbi 454 from chevy. But than motor has no trouble getting enough fuel through the stk 3/8 gm line and it's been 6500 through 3 gears lots of times in the last 10 years.......any more I match the feed and return sizes just to know there is no issue. All my street and marine motors that use electric pump get returns
Obviously you have a lot of experience here & I've never done this & so I'm just thinking out loud but it seems with a return the same size as the feed that'd provide the path of least resistance & even w/the engine pulling fuel could possibly bleed off enough pressure & starve the engine for fuel vs. a smaller return that would create some back pressure in the supply. You haven't found that to be the case but...
No the return is only what the motor doesn't use.........the regulator feeds the motor first.......then only sends fuel down the return once the feed line is full and up to the set pressure...........the problem comes especially at idle when your not using much fuel but the pump only know to pump full volume and pressure.........unless your spending big bucks on the newer variable output pumps and drivers.........so the pump tries to push 100% capacity all the time......but lets say at idle you might be using 2%........leaving 98% to go back........if you can't return 98% back you could see the fuel pressure actually rise 2 or 3 psi depending on the strength of the pump causing flooding. The better of pump you put in the more the return balance becomes an issue.........on a holley red that can only make 7-8psi might not be an issue on pump that can make 60 psi you better have it right.......... Remember pressure is only a measurement of resistance to flow. On the same note depending on the pump you choose the regulator needs to be able to handle the same volume of fuel through it or there is another point of issue
So I have been weighing the various options people have brought up and it seems the simplest and most cost effective for me is the RobbMc pump with an upgraded 1/2" supply. That's including the pickup in the tank, tank to pump and pump to carb lines. Buying steel braided/TFE supply lines solves the line bending problem I was dreading. This has been an informative thread, thanks to all who are chiming in.
I run a 1/2” stainless fuel line from the tank all the way to my carburetors and the A-1000 fuel pump with a short 3/8” return line back to the tank and it works great.
They do take time and it's not cheap.......but should never need done again I've used plenty of push lock b4 with no issues on fuel.......had a few fail at the fitting on oil........I now only use the coated ptfe for oil lines too
I have been using Areoquip push lock hose for fuel for 20 plus years, with no issues. https://www.summitracing.com/parts/aer-fcv0820?rrec=true I am no fan of the cloth braided stuff. And Teflon liner is not required for gasoline. JW
Thanks for the tip Jim. I had been looking for hose to use that wasn't just the black stuff you can get at auto parts stores. It won't be a show car but I don't want it to look like a complete hack job either.
Larry, Will a Q-Jet tolerate that pressure at idle w/o overcoming the needle and seat? Thanks! Ranger Aiken, SC
Yes, the later Q-jets have a much better float assembly. No problem whatsoever. I have a 7042240, a 1972 carburetor.
