69 SB Fuel Line Routing

[bheston]

I couldn't find much detail on the fuel line routing for my 350/300 SB.  My routing does not seem correct but "kinda" matches the AIM.  Most 350's I see have a primary line running from the carb toward the center of the motor to a fuel filter.  That line passed behind the water pump down to the fuel pump.  I attached a couple pics.  I can't tell where the smaller fuel line goes and it's purpose.  I have generic fuel filter installed (former owner) and it seems to be starving for fuel.  I just want to eliminate that as a problem.  Here is my confusion:

- Where does the smaller line on the fuel filter go?
- Did all 350's have the fuel filter and fuel line running behind the water pump?
- Is the AIM diagram a different version but still correct?

[william]

'69 Camaros built with Quadrajet carbs used a large in-line AC fuel filter. It also served as a de facto fuel reservoir and required the smaller fuel return line to the fuel tank. You must also have correct sending unit for the tank.

This is covered in the AIM, section L48 page A3.

[ko-lek-tor]

That return was required because engineers determined/ discovered that it took very little fuel pressure to overcome the needle / seat of a q-jet causing overflow of fuel out of the vent. As long as the carb has not been over tightened and has had necessary bottom well plugs epoxied, these are very good carbs.
Yes, both lines go behind H2O pump. Yours look correct.

[bheston]

The pic in the original post wasn't of my car but an example I thought was correct.  It looks like someone replaced the original fuel pump with a 3-legged rascal  .  I would like to convert it back to as original as possible.  Here is what the fuel pump look like and the three lines from my actual car.  Is this more effort than what it's worth?

 

[ko-lek-tor]

OP send me a PM.

[bheston]

If someone could kindly send a pic of how the small return line from the fuel filter connects to the return line down by the fuel pump, that would be very helpful. I’m guessing it’s a rubber hose and red clamps?

[william]

I do not know the application for that pump. It is not for a '69 Camaro.

The smaller diameter return line goes back to the sending unit in the fuel tank.

[Mark]

That fuel pump look like a marine unit, that small vent line usually gets connected to the air horn of a marine carb, so if the pump diaphragm ruptures any leaking fuel goes into the carb and gets burned instead of dumping into the bilge and blowing up your boat.

[rich69rs]

I couldn't find much detail on the fuel line routing for my 350/300 SB.  My routing does not seem correct but "kinda" matches the AIM.  Most 350's I see have a primary line running from the carb toward the center of the motor to a fuel filter.  That line passed behind the water pump down to the fuel pump.  I attached a couple pics.  I can't tell where the smaller fuel line goes and it's purpose.  I have generic fuel filter installed (former owner) and it seems to be starving for fuel.  I just want to eliminate that as a problem.  Here is my confusion:

- Where does the smaller line on the fuel filter go?
- Did all 350's have the fuel filter and fuel line running behind the water pump?
- Is the AIM diagram a different version but still correct?

Also, my understanding, which is what the AIM shows in your 2nd attachment, is that, from the factory, the fuel line section between the fuel pump and carb was hardline (steel tubing) with screw fitting connections - no "rubber" fuel line with clamps used on the discharge pressure side of the fuel pump due to the increased potential for a leak and possibe fire.

If you haven't seen it, the following CRG report on Camaro Carburetor Useage might also be helpful.  http://www.camaros.org/carb.shtml

Richard

[JKZ27]

 bheston, here is a pic of mine.

John

[bheston]

Perfect! Thanks John.

[toddbarrett]

'69 Camaros built with Quadrajet carbs used a large in-line AC fuel filter. It also served as a de facto fuel reservoir and required the smaller fuel return line to the fuel tank. You must also have correct sending unit for the tank.

This is covered in the AIM, section L48 page A3.

Hi William, Can you explain a bit more about the correct fuel sending units you mention for the L48 350. When looking at the AIM on UPC 8 - B5, they show the fuel sending units but only spec out a "V8" or an "L6". Is there a difference for the L48 with the large in-line AC Delco fuel filter canister?

My car has strange fuel readings (shows empty when there are 10 gallons left, and never gets to "F" when I fill up), so I replaced the fuel sending unit, but nothing has changed. Still getting incorrect fuel readings at the gauge.

Thanks in advance!
Todd

[william]

The sending unit used for '69 Q-Jets has 2 hose bibs; one for the return line. Fuel line routing is shown in the L35 section.

[toddbarrett]

Thanks for the info. My set up seems correct; I wonder if the gauge itself could be faulty?

Todd

[z28z11]

2 possibilities - 1) If the sending unit is a reproduction, some have a terrible reputation for accuracy. If not, an original could be a victim of old/bad gas. 2). Ground wire is dirty/corroded/bad connection. Make sure the connector is not frayed and is snug on the fastener.

Rule these out and see if it doesn't correct the gauge reading.

Regards,
Steve