z06roadkiller

Guys:
I'm in full restore mode with a 68 427. It was originally a 4-barrel carb set up and a previous owner upgraded it to a tri-power. I plan on keep it a tri-power as I don't have intension to be a NCRS show car (no tank sticker); however I'm keeping it as true original as possible.

This leads me to my tank question. I pulled the tank and it has the vapor return line version. As I rebuild the frame I'm planning on replacing the fuel lines as part of the build. Should I:

(1) absolutely keep the vapor return line system and buy that tank version or
(2) scrap the vapor line all together (thus buying the non-vapor line version tank)

Note: The vapor return line in my current set up is coming off the fuel filter which is now after the fuel pump but before the supply line to the carbs.
I'm going to get my tank and components for this from Quanta Products (FYI).
I guess my main question relates to the "real" functionality of the vapor return line with the tri-power set up for '68....i.e. do I need it??? (the car was running fairly well before the rebuild)
Thx,

ctmccloskey

Hello there z06roadkiller,

I have an early (October, 1967) 1968 L71 Corvette that came to me with a single four barrel carburetor. The fuel tank I have in the car looks like the original and it too has a vapor return line. I have it capped off since I have nothing to connect to it and I got tired of having fuel leak out of it when driving with a full fuel tank.

If your car came with the fuel vapor line on the fuel tank then I would probably replace it with the same kind of fuel tank. If you don't use it then simply cap it off but it would be closer to what the car came with. The tank that came with my Corvette is a 20 gallon tank and has the outlet on the bottom of the tank. The plate that mounts the fuel level sender is mounted on the bottom of the fuel tank.

Best regards,
Chris

wwiiavfan

Are you talking about the same thing?
You mentioned a "vapor line" coming off the fuel line before the carbs. That would be liquid fuel return to the tank, not vapor.
Fuel vapors, on '69 (? I think) and later models are taken off the tank on the top left side by the fuel separator valve and brought forward on the left side of the chassis to the charcoal canister inside the left front fender.

z06roadkiller

wiiavfan
I can tell from the way my system was "jerry-rigged" it was not stock. I'm calling this a vapor line for the fact that it's a recycle line from the way I see it. Here's better description of my set up.
(1) One line coming from the fuel pump to the fuel filter
(2) two outlets from the fuel filter WIX 33041 filter (told that its for a older Mopar not Chevy)
(3) main center port goes to the fuel rail
(4) second port goes to a line running side-by side to main fuel line from gas tank

In the rear passenger side I have two lines that both look to be running on the same part of the frame to the front where I can see both side-by-side again. I did NOT follow these two lines the entire length of the frame; so I assumed that this was a vapor return line for some type of emissions.

I found out from recent car restore work my car has 2/15/68 chalk markings inside the truck roof (t-top coup car). I'd like to set this up right but I'm more confused by your description as I don't have that fuel separator valve. I have the tank as described from Quanta Products as: GM-33C ( https://www.gastanks.com/1968-July-6...ctinfo/GM-33C/)

I'm going to trace down these lines tonight to verify that are both the same running the length of the frame on the passenger side.

But is seems to me from both the replies that this vapor line off the gas tank is a tank vapor pressure release line (with a dump to a carbon filter) and not a vapor recycle line from the carbs which is confusing be to the real function of that line off the gas tank.

wwiiavfan

I’m pretty sure the ‘68 didn’t have the vapor recovery system that the ‘69 and later have, with the charcoal canister. So yes, your tank, if correct for a ‘68, won’t have the vapor valve on the drivers side. You also should have a vented gas cap.
Both lines from the tank to the front on the passenger side carry liquid fuel. The larger one brings fuel to the pump, and the smaller one takes excess fuel back to the tank.

Torqued Off

I don't believe 69 Corvettes had a "vapor return" line on the left side, i.e. charcoal canister, etc. It does have a fuel supply line AND a fuel return line on the right side of the frame. 69 Corvettes had a vented gas cap.

grantstigers

To put it simple....true as possible......then it came with vapor return line. Two lines for a single 4 barrel set up

Again if you want it true as possible then keep the vapor line and cap it off. Maybe one day you want to take off the tri power set up and put in a 4 barrel then the option of the vapor line comes in.
On a foot note a 68 4 barrel is about 1000.00 as a core. Rare carb indeed.
Also I feel the car represented as previously from the factory has more merit than if you start adding non factory items.

If you want to keep the tri power set up. the 400 hp and 435 hp tri power cars had a single fuel line and did not use the vapor line.

But if you don't want to mess with it and keep it simple then scrap the dual lines and put in a single line as a true tri power set up is. But remember you do it once this way and can't go back unless the frame comes off again and another vapor tank set up again and spending more money!!

Hope this helps
Grant

z06roadkiller

Grant
From all the post reading I've done on this topic since posting you are spot on. In '68 the only vettes that had the return line was the 4-barrel QuatraJet set up (L36). This car WAS an 427 390HP L36 as I mentioned that was converted in its life to a Tri-Power Holley carb set up. The Holley carb systems back then didn't have the ports on the carb to return "vapor" back to the gas tank. This was very early emissions "thingy".

Since I'm going to do the frame off next winter and I plan on keeping it a tri-power carb set up I've got to choose:
(1) But a new gas tank with the vapor port and tap it off to possibly change it back someday or
(2) screw the vapor port on the gas tank and go all out like it was an true L71

Thx....

ddawson

I did the same thing. I kept the filter and return. Just made the lines work with the holley.

whitehause

I have a 68 L71 ( as confirmed by the tank sticker) it's NOM, but since the tank had the sticker on it I assume it's original, and no fuel or vapor return system. Just one feed line running to the front.

ctmccloskey

In 1968 the 300 & 350 hp (327's) and 390 hp (427) Corvettes used a return line and the higher powered 400 and 435 hp corvettes had a single line coming out of the fuel tank and did not use a return line. This was the standard for the 1968 and early 1969 models. I just found that my Early 1968's fuel tank did not tolerate ethanol very well so I have had to replace mine. The vapor return system did not appear until a few years later it appears.

At Zip they get $290 for the fuel tanks with the logo on them and $190 for the non logo fuel tanks. I am putting a Non-logo tank back into my car as I really have no desire to go the NCRS route and the logo is not visible on the tank when it is installed.

kodpkd

If you read on this forum about all the carb/fuel issues....... Many many of the issues come from not having the proper fuel return line.

kossuth

Yep, some of the 68's have the 3rd line even the big block cars do. My brothers 68 does and it is a L36 big block car. 68's are a weird car to figure out what is an isn't legit due to the number of production run changes.