1970 -6 Gas Tank Supply Pipe Hose Bead Question, Morphed into: “Does the OE fuel return system cool fuel going to engine?” uh … No Options

[Rufus]

Hi Folks - I have the entire fuel system out of 9140431482 back to the Webers for update, cleaning, etc. (Webers already reinstalled after thorough cleaning.) The gas tank fuel outlet pipe has no hose bead.

Is this normal? Seems odd there wouldn’t be one.

Thanks,
Bob

[Rufus]

Considering this further. I’m installing a Tangerine Racing SS 3/8” fuel line through the tunnel. My Airtex E8016S fuel pump is located at the rear.

So I’m wondering if a bead on the tank fuel supply pipe serves any real purpose.

The Tangerine fuel line on the other side of this connection has a bead, there’s no significant fuel pressure, and I’ll use Permatex’s fuel resistant non-hardening sealant on the connection. A clamp, a generous hose overlap, and the limited tube movement on either side of the connection will protect against the hose coming off.

(Hope this all makes sense.)

Your thoughts are welcome

[mate914]

Considering this further. I’m installing a Tangerine Racing SS 3/8” fuel line through the tunnel. My Airtex E8016S fuel pump is located at the rear.

So I’m wondering if a bead on the tank fuel supply pipe serves any real purpose.

The Tangerine fuel line on the other side of this connection has a bead, there’s no significant fuel pressure, and I’ll use Permatex’s fuel resistant non-hardening sealant on the connection. A clamp, a generous hose overlap, and the limited tube movement on either side of the connection will protect against the hose coming off.

(Hope this all makes sense.)

Your thoughts are welcome

Its kinda hard to know what your talking about with out pictures.
This "bead" word, what does it mean? Pictures of your 6 are also welcome. I just put a 2.7 with mod-s cams J&E pistons with IDA webers and MSDS headers. It sounds so smooth..

Matt

[gereed75]

I know exactly what you are asking but I’m not sure if there is a “bead” that is “hose barb” or not. Been a long time since I was in there.

But regardless, a good tight hose and hose clamp ( maybe two) should do it.

[gandalf_025]

Bottom of the gas tank from my 6.

Never been touched..

[rgalla9146]

That is exactly how they should look.
Don't forget the metal sock inside the tank on the larger feed line.
Believe it or not, I think there were no hose clamps there from the factory !
Be sure to point those nipples in the right direction for easier hose connection.

[brant]

Moving your pump forward is a good idea
Pumps push. But don’t suck that welll

[Rufus]

Bottom of the gas tank from my 6.

Never been touched..

Perfect! That’s what I have (except no pipe for a return).

Now I’m sure I’m headed in the right direction.

Re the strainer (sock) on the inside of the supply line. That was one of the many flaws I’m correcting. Mine was broken in 2 and disintegrating, tank contained countless (paint?) flakes from “restoration”, AN 6 SS braid hose deteriorated and leaking fuel vapors into the cabin near the shifter, and an IDA’s inlet filter was torn allowing debris, paper towel and fabric fuel line reinforcement cuttings into the floats.

Hose “bead” vs “barb”? It’s a relatively minor difference in geometry. A bead is a smooth bulge rolled into the tube vs a barb which is usually multiple sharp “teeth” cast into the nipple for enhanced hose retention. A clamp tightened behind the bead retains the hose like the sharp edges on a barb do.

Thanks for all your input. (IMG:style_emoticons/default/smile.gif)

[Rufus]

Moving your pump forward is a good idea
Pumps push. But don’t suck that welll

Thanks Brant. I agree100% and considered doing that. I decided not to just because I hope I’m finally at the end of a 3 year rabbit hole of fixing problems (beyond fuel system issues cited) to get the car drivable. Maybe exhausted, maybe lazy, but didn’t wanna face wiring to the front for the pump now :/

Other factors making me a little more comfortable leaving the pump in the less desirable back: the Tangerine fuel line has a slightly larger ID than the AN -6 SS hose it replaces. #2 I’m taking the opportunity to lower the pump mounting an inch or so in back so there’ll be slightly greater pressure “head” at the pump inlet

[brant]

Carbs like cool fuel
Consider putting the return back for that reason

[SirAndy]

Carbs like cool fuel
Consider putting the return back for that reason

(IMG:style_emoticons/default/agree.gif)

[Rufus]

IMHO putting the return back in will increase fuel temp; not reduce it.

[technicalninja]

IMHO putting the return back in will increase fuel temp; not reduce it.

This is correct for FI cars. Carbed stuff not so much. Increasing pressure on anything gaseous or liquid increases its temperature. 60 psi is definitely a heat creator.
3.5 psi, not so much. I bet it would be hard to see a temp difference.

Being back in the engine compartment for any length of time will heat the fuel and a return would help. A "cool can" would help as well.

I'm a huge believer in moving the pump to underneath the tank. Brant is spot on but...

This is a real 6. I'd be loath to make any changes over stock and I'd make DAMN sure that any changes I made could be easily changed back to stock without any evidence left behind.

The fuel return for FI cars went through multiple changes over the decades.
The increase in tank temps increases evaporative emission badly enough that Mercedes actually routed the AC low side suction line through a fuel cooler. This is bad- assed and I'd have had that cooler on the inlet side to cool the fuel before it hit the injectors.
Mercedes put it in the return line just to cool the fuel returning to the tank.

Modern shit mostly has the pump and the fuel pressure regulator in the tank and this system is labeled "dead head" as all the fuel going to the engine will be consumed.

All of these scenarios are trying to keep the fuel in the tank as cool as possible for emission reasons.
It's not for the betterment of the engine...

[brant]

IMHO putting the return back in will increase fuel temp; not reduce it.

Nope

Fuel sitting above the motor gets hot
Having a return lets the warm fuel back into the cool reservoir of cool in the tank
The fresh fuel from the tank is cool


In racing they even sell a fuel tank you surround with ice to lower the temp further

Cool fuel makes more horsepower
Warm fuel boils and creates vapor lock

A return line absolutely cools the fuel without any doubt

Carb cars respond even better to cool fuel due to the lower pressure of a carb system

FI systems have reduced fuel boil and vapor lock due to the high pressure they operate at

A return system/line was the factory design
They did this for a reason Even on a carbed 914/6



Few people outsmart the factory engineers

[wonkipop]

IMHO putting the return back in will increase fuel temp; not reduce it.

Nope

Fuel sitting above the motor gets hot
Having a return lets the warm fuel back into the cool reservoir of cool in the tank
The fresh fuel from the tank is cool


In racing they even sell a fuel tank you surround with ice to lower the temp further

Cool fuel makes more horsepower
Warm fuel boils and creates vapor lock

A return line absolutely cools the fuel without any doubt

Carb cars respond even better to cool fuel due to the lower pressure of a carb system

FI systems have reduced fuel boil and vapor lock due to the high pressure they operate at

A return system/line was the factory design
They did this for a reason Even on a carbed 914/6



Few people outsmart the factory engineers

spot on.


the vapor lock problem in the 4s is in the short section of line between the tunnel exit and the fuel pump. (gets even worse when you do the metal line replacement of the original plastic lines - i know). solution = wrap the section of line to the pump in reflective insulation. since i have done that i have not had a vapor lock problem with the pump still in original position. the heat source that boils the fuel in a 4 is the magnesium cooling fan shroud. when you switch off after a good hot run all the residual heat in the engine conducts to the cooling fan shroud and then radiates. prime target of the radiation is those short runs of fuel line.

a 6 does not have that vicious heat radiating fan shroud.
sure there is a hot engine block, but suspect its not such a localised heat radiator.

did 6s even suffer from vapor lock?

though in fairness to the mental powers of the original engineers, they did manage to outsmart themselves with the fuel pump location of the 4 for many years until they finally gave up and admitted defeat. i guess they did not have insulated wrap back then. (IMG:style_emoticons/default/biggrin.gif)

[brant]

Over 40 years of this hobby I have not heard a lot of -6 cars having vapor lock


However
Todays fuel at the pump is really really crappy stuff
It also has a lot of water in it within a weeks time of purchase

It is really more susceptible to boiling than the fuel that existed when these cars were designed

Really crappy stuff


So with modern fuel you need a return line in a fuel system much more than in the past

[brant]

Duplicate post

[Rufus]

@brant “Fuel sitting above the motor gets hot”

Just so I’m sure I understand, where’s this fuel that’s getting hot?

[brant]

@brant “Fuel sitting above the motor gets hot”

Just so I’m sure I understand, where’s this fuel that’s getting hot?

In the fuel lines that run over the motor to feed the carbs

The floats in the carb restrict how much can enter the bowls (flow rate)
A return line allows the excess to return to the tank for cooling and less heat absorption
No return line parks this excess fuel to cook

The excess waits in the line over the motor
I have not measured temps. But I’ve felt the hot fuel. It’s got to be 20 degrees hotter than what’s in the tank

Why do you think the factory bothered to plumb a return line into a six?
I find it funny that people don’t want to modify a six…. Even pump llocation. But don’t think twice about modifying a return system that actually shows in an engine bay

[Rufus]

@brant The factory return went from the fuel pump back to the tank. Fuel downstream of the fuel pump, I.e. in the lines you describe and in the floats, was not in the return circuit. What am I missing?