First Generation Firebird
Posted By: cme469 Fuel sending unit - 02/08/19 06:13 PM
Some sending units have the 1/4” vapor return line and some don’t. My 69 has it. Have read that cars with 4bbls had it, or was it a production year thing? Do your 67s and 68s have it? And, if you do have it do you need a vented gas cap?
Posted By: firebird69racer Re: Fuel sending unit - 02/08/19 10:15 PM
My 69 350 2bbl TH-400 has the vent. Mine is a Ca. car also, so that might be why it has it
Posted By: HaroldB Re: Fuel sending unit - 02/09/19 12:22 PM
My 68 400 HO has the vapor return. All 67-68 use the vented gas cap.
Posted By: hokie1984 Re: Fuel sending unit - 02/09/19 01:31 PM
My understanding was it was all 400s and all cars with A/C. My 1967 Sprint (with A/C) has a return line.
Posted By: Bob S. Re: Fuel sending unit - 02/09/19 02:00 PM
That's what I thought too hokie. My original 326 car, 2 bbl, no AC doesn't have it
Posted By: JamesM Re: Fuel sending unit - 02/09/19 03:44 PM
The 69 has the gas tank vented through a nipple braised to the neck of the fill pipe and then you usea non vented cap .
Because of where the gas fill neck is if you used a vented cap every time you accelerated gas will spew out the vented cap.

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Posted By: Firebob Re: Fuel sending unit - 02/09/19 04:23 PM
Wade, that's odd because my 69 350 2bbl 4sp didn't come with a return line. None in the sender and none on the fuel pump. I just assumed that base 350s w/o AC didn't have them. Mine as an early build.
Posted By: firebird69racer Re: Fuel sending unit - 02/09/19 04:49 PM
Originally Posted by Firebob
Wade, that's odd because my 69 350 2bbl 4sp didn't come with a return line. None in the sender and none on the fuel pump. I just assumed that base 350s w/o AC didn't have them. Mine as an early build.



I forgot to say mine was an A/C car and also has the nipple on the filler neck for the vent. That might be why
Posted By: JamesM Re: Fuel sending unit - 02/09/19 05:21 PM
Yes mine was a 69 350 with A/C and it has the return line too.
It was built at the Van Nuys California plant in the third week of September 69
Posted By: Bob S. Re: Fuel sending unit - 02/09/19 05:57 PM
I think we’re confusing return lines with vent lines
Posted By: Firebob Re: Fuel sending unit - 02/09/19 10:27 PM
Ok. That makes more sense then because it was my understanding that the return line was included on the 400s and ac cars. Probably the HO cars as well. Could be in 69 only the 2bbl cars and the base ohc6 cars w/o AC came with no return line. I wonder if all 4bbl cars came with the return line. Ooooooo, that sounds like it makes mine all that much more rare! Probably 1 of only 67,000 or so builds. Lol.
Posted By: jusride Re: Fuel sending unit - 02/10/19 01:59 PM
My 1968 350 AC car has it. It runs to a charcoal filter under the driver side fender. My car was also built in the Van Nuys plant in July 1968.
Posted By: cme469 Re: Fuel sending unit - 02/12/19 04:41 AM
My 69 was originally an HO 350 w/manual trans and no AC. It has the 1/4” return line. The filler neck vent was not intact or had been deleted. The reproduction tank has no vent in the neck. Will the return line act as a vent, or to be safe should I use a vented cap to prevent damage to the naw tank from “oil canning” due to exessive vacuum?
Posted By: Firebob Re: Fuel sending unit - 02/12/19 01:49 PM
I think you're going to need a vented cap. Seems that they deleted the vent in the neck mid year on 69s( at least that's what I remember hearing). I think they used a vented cap after that, return line or not.
Posted By: cme469 Re: Fuel sending unit - 02/12/19 03:40 PM
Thanks Robert, do you know how the vent was deleted? Mine still had the nipple on the neck but it was plugged. I always assumed that a previous owner just crammed something into it. It did have a non vented cap when I got it. ???
Posted By: Gus68 Re: Fuel sending unit - 02/12/19 04:04 PM
Vent your tank using the
Originally Posted by JamesM
The 69 has the gas tank vented through a nipple braised to the neck of the fill pipe and then you usea non vented cap .
Because of where the gas fill neck is if you used a vented cap every time you accelerated gas will spew out the vented cap.


JamesM has it correct for venting. As Harold states, "vapor return", is another way to call he return line because tha's what the return is there for. You will never get vapor lock again. I would recommend putting it in no matter what the size engine you have in it. If you ever upgrade to 4bbl or bigger engine it's there ready for you.

x3 Do not put vented cap on 69 tank.
Posted By: Firebob Re: Fuel sending unit - 02/13/19 01:05 AM
None of the aftermarket tanks have vents. How would you( or anybody go about venting a non vented tank without using a vented cap?

I ran a vented cap on my 69 before. It's been a long time but I don't recall having any issues.
Posted By: Gus68 Re: Fuel sending unit - 02/13/19 02:45 AM
Originally Posted by Firebob
None of the aftermarket tanks have vents. How would you( or anybody go about venting a non vented tank without using a vented cap?

I ran a vented cap on my 69 before. It's been a long time but I don't recall having any issues.


The fuel tank on 69 has filler tube at the
rear sloping down because it’s behind
lic plate. When you excellorate away gas pours
out the vent hole.
Posted By: cme469 Re: Fuel sending unit - 02/13/19 05:11 AM
I’m assuming that like so many of the repro parts that are advertised (many incorrectly) for “Firebird-Camaro” that the repro tank is aimed at the Camaro. If so, what did the Camaro use? Or did they have the vent, or vented cap? Also, it seems like the hole in the vented cap is so tiny that not much gas could escape.?? Could that be the case? Does gas escape out the neck vent tube under hard acceleration? Still not sure which way to go.
Posted By: Gus68 Re: Fuel sending unit - 02/13/19 05:50 AM
Originally Posted by cme469
I’m assuming that like so many of the repro parts that are advertised (many incorrectly) for “Firebird-Camaro” that the repro tank is aimed at the Camaro. If so, what did the Camaro use? Or did they have the vent, or vented cap? Also, it seems like the hole in the vented cap is so tiny that not much gas could escape.?? Could that be the case? Does gas escape out the neck vent tube under hard acceleration? Still not sure which way to go.


I recall some time ago someone did have that issue. Try looking harder for a OEM or NOS tank. I got a NOS tank for my bird and my Catalina.
Posted By: Firebob Re: Fuel sending unit - 02/13/19 04:39 PM
Good question. I never thought to ask how the camaros were arranged. I'm not exactly sure what Pontiac did after they did away with the vent tube in the neck either. They must've fixed it somehow. Maybe go to an aftermarket tank maker and ask how they control venting.
Posted By: Gus68 Re: Fuel sending unit - 02/13/19 06:29 PM
Originally Posted by cme469
I’m assuming that like so many of the repro parts that are advertised (many incorrectly) for “Firebird-Camaro” that the repro tank is aimed at the Camaro. If so, what did the Camaro use? Or did they have the vent, or vented cap? Also, it seems like the hole in the vented cap is so tiny that not much gas could escape.?? Could that be the case? Does gas escape out the neck vent tube under hard acceleration? Still not sure which way to go.


Have a look at this thread: https://firstgenfirebird.org/forums/ubbthreads.php?ubb=showflat&Number=210990
Posted By: Gus68 Re: Fuel sending unit - 02/13/19 09:29 PM
If you want the original with the tube, a guy at PY has one.

https://forums.maxperformanceinc.com/forums/showthread.php?p=5991664#post5991664
Posted By: cme469 Re: Fuel sending unit - 02/20/19 09:03 PM
Thank you all for your replies. Have given some thought to this, and for originalities sake, I think I’ll install the vent nipple into the filler neck (already have an aftermarket tank as the original was damaged). However the picture JamesM put up seems to show it in a different location than my original tank. If looking from the rear, the nipple on my original has it at about the ten o’clock position. Looks like it’ll line up good with the tube to the trunk from there. What do other 69s have?
Posted By: JamesM Re: Fuel sending unit - 02/21/19 01:09 AM
I bought mine in 1978 and I’m sure it is the original tank and has never been out of the car but with all these cars it may depend on if it was done on a Friday or a Monday or what plant it was built at .
Or beginning of the model year or the end because the 69 was a one year wonder it's hard to say.
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