Hey guys, while my engine is out I am doing some planning. I live in GA where A/C is a must and my truck was a heat only truck, This thread is about drivability in all temps hot and cold. However I don't know much about fuel systems. Heres my setup stock mechanical fuel pump, oe fuel lines, tank, 347 stroker, QF 600cfm Vac sec carb. I heard a few things about dead head systems and fuel systems with a return line. But there is nothing really clear on how they work or if they will benefit my setup. All I "THINK"I know is cooler fuel temps and better drivability. Since the engines out this could be the best time to run lines etc. Also side note if it affects advice. I will be adding A/C with the Nostagic AC kit. Look for a a write up in the near future.

 

A fuel return line (with a return style regulator) helps to keep the fuel cool while it is recirculating whats not being used instead of it sitting in the lines under the hood.. It also allows the fuel pump (electric is needed) to run without restriction and therefore cooler. Getting the fuel pump off the engine also aid in keeping the fuel cool. A/C adds a lot of heat under the hood and might require a bigger radiator.

 

Can the emissions return line that is already going to the tank be used as a fuel return line if one were to go with this kind of setup?

OP, if you haven't already gotten parts, consider Vintage Air.

 

I appreciate Vintage Air recommendation but they do not make a kit for our trucks and a customized universal came out to 500 more then the Nostagic A/C kit that exactly fits in our trucks.
https://nostalgicac.com/complete-ac-...c-defrost.html

Also I have a Heavy duty Eagle Rad good for 650 HP so I think I am good.

 

I am going to use a Nostagic Air kit on my truck too, I have factory AC so just new parts. My truck is a Camper Special and has a HD radiator BUT I live in Phoenix (only 106 today, that means about 125-130 on the asphalt). Are you using an electric fan? I understand I may not be able to use the AC in June-August just because of the climate I live in even with a fan but it reaches into the 90's in March and can be in the 90's on Thanksgiving so it would be nice to have it.

 

My friend and I installed a Sniper setup on his car and we used the charcoal canister line port on a stock tank for a fuel return line. It worked just fine. But don't forget that you've got to vent that tank somehow, or you'll pull a vacuum on the tank, and get fuel starvation.

I've only used a regulator on one mechanical fuel pump setup. It was deadhead. Can some smart guy confirm for us if a standard 7-9 psi mechanical pump even has enough pressure after the regulator to push fuel back to the tank?

 

The engine and underhood side of the return system is the easy part to do, running lines under the truck and to the tank(s) is the crappy part, imo. Having the engine out only helps a little. But if you got the time and money to do it, might as well while it's apart already.

 

Isn't an EEC tank already vented with the second tube next to the filler tube?

 

Yes, but the tube/hose adjacent to the filler neck only vents when the filler cap is removed.

 

You know what, now that I think about that, I can only speak for mine. It only vents when cap is removed during filling. For all I know, others may vent all the time. Either way, if you use the emissions vent for fuel return line, you need to confirm that the tank is equalizing while the pump is pulling.

 

You'll need to use a vented gas cap for a non-EEC tank. They're supposed to vent with the cap on.

 

And less fuel pressure at the inlet of the carb. And probably a cooler running pump of either type.
Even in a simple basic system without an actual regulator, a return port after the pump moderates the pressure and is less likely to push against the needle enough to put excess fuel in the float bowl when bouncing around.
Probably not a big deal on the street (and carbs have been working fine without them for all these years) but in a work or off-roading environment it can make a nice difference.

Probably better with an electric pump, but by no means necessary. Ford and GM both had return systems back in the sixties and seventies on some vehicles (primarily high-altitude and hot region deliveries, and turbo engines) with mechanical pumps.

I'll take the opposite road of the others and just say "NO" you can't do that.
Ok, you can physically do it, and depending on how yours is set up, it might work with never a bit of trouble. But hopefully you're leaving your evap canister in place and in use, in which case you want to be sure how everything is plumbed so as not to allow any liquid fuel from the return system get into the charcoal canister. Bad juju for the charcoal.

The vent tube is sometimes a convenient spot, but there are other ways. Attaching it to the filler neck. Using some kind of a "T" fitting slipped into the fill-vent hose (I think it's 5/8" usually?) or, more trouble but effective, would be a fitting right into the tank or sending unit plate.
When Ford did it on some trucks they had a special sending unit model that had both the feed and return coming right out of the round plate. Just like they do on so many other modern vehicles until recently.
Some fuel filters had the return feed built into the output side, which then had a line back to the tank with the extra fitting.

No problem. It could do it with 1psi. It's got volume on it's side as long as there are not enough restrictions to fight the pump,the normal pressures are fine.

Paul

 

. Worth the watch