need a blazer expert...

[frostie_122]

I'm putting a lt1 in my 72 blazer. I was going to use the vapor canister line for a return line. Looking at the factory tank I see the fuel inlet and vent, two vents going into the bed floor, out of the bed floor one line going foreward to the canister I think...(I pulled the motor before I looked), and one out of tank foreward to the motor...

My questions: What is the cylindrical tube out of the bed froor that the three hoses are going into? Can I cap all that off and just have the line foreward and return, and the filler and vent? Maybe use the motorcycle vent cap I saw in another post? Not concerended about gas smell just fuel injection functionality.

thanks in advance

[71RestoRod]

That tube is part of the vapor recovery system. It separates and traps the vapor using two lines that lead to each side of the fuel tank. You can stub out the vapor tube and re-route the canister line to the fuel tank but if you do check and make sure that you're using a vented cap.

Here's a link to a previous thread on the vapor tube plumbing and recovery system:

http://67-72chevytrucks.com/vboard/s...d.php?t=187860

[frostie_122]

... I guess I'm still a little confused. I understand where everything is going, what it does and what it's for. If I cap the the left side vent and use a motorcycle style check valve vent in it's place and cut the line from the canister up front and plum it into the second vent as the return line, would this work. The motor is a 1993 lt1 with 43 psi fuel pressure. I'm not so worried about gas smell. I have a fuel safe style gas cap inside the truck as well. I don't believe it's vented, but not sure.

Thanks once again.

[frostie_122]

here are a few pics of the gas cap. winter time the top is on summer its off...

[frostie_122]

..on another thought could I leave the driver side vent that goes to the cylinder in bed attached and detach the passenger side vent and use it as the inlet for the return line... this would eleviate the need for the one way valve. Whats in the cylinder in the bed? Just an open tube? Charchoal?

I usually never put more than 20 bucks in at a time so I'm not worried about the two vents for sloshing reasons...

thanks

[71RestoRod]

The cylindrical vapor tube in the bed is nothing more than a standpipe. The vacuum line runs up to and pulls the vapor off the top of the tube. This prevents any raw gas entering from the tank lines from being pulled into the charcoal canister.

It's a good system to have in place and not difficult to hook up but if you choose to bag it, just make sure that you have an open two-way vent and not a closed system or check valve. I've seen gas erupt from a filler neck like a geyser when the cap is removed from an improperly vented tank. This can happen even with a mostly empty fuel tank from pressure build-up. It's the last thing you want inside your truck. Picture your lawn mower gas can in the hot sun.

You could use the vapor tube as a vent, or perhaps run a line off of the spare tank vent up the bedside or alongside the filler hose and cap it off with a plastic differential-style vent cap.

[frostie_122]

would the driver side tank vent that goes into the vapor tube be suffecent? that would vent out to the other two tubes that would be cut back to a few inches off the vapor tube...

[71RestoRod]

Originally Posted by frostie_122

would the driver side tank vent that goes into the vapor tube be suffecent? that would vent out to the other two tubes that would be cut back to a few inches off the vapor tube...

First I would re-plumb the whole thing if you haven't already... I'm sure you've discovered how rotted out both the steel and rubber lines can get. Be suspicious of the fuel and vapor lines that lead to the engine compartment. You certainly don't want crud in your fuel system.

Run the drivers side vent to the same low-side entry point on the vapor tube. Cap off the vapor tube passenger side entry and leave the canister line open to vent (or worst case to drain if necessary).

Having said all that... the better solution, particularly given your filler and that you already have the vapor system in place, would be to drop the tank, pull off the fuel sender and drill a hole in it for a fuel return fitting. Even without the charcoal canister hooked up to vacuum it provides a nice filtered vent. JMHO.

[frostie_122]

yeah i dindn't think of that... as far as a pressurized system do I have to replace al the vent hoses with injection line as well? The hard lines I was planning on using just because they are there.

Obviously the "right way" to do it would be gut the thing and start over. I'm on a budget that was supposed to be buy the motor and put it in. The motor ws worked, super sludgy and needed some love. Now its bored over, fully rebuilt and with a cam. I'm not trying to take shortcuts but I'm REALLY over budget and it's my daily driver.

[71RestoRod]

The tank itself isn't under pressure, and the return line doesn't require anything special so I wouldn't use high dollar line for any of that.

3/8" hard line would be an upgrade and is pretty inexpensive if you have a tube bender and a flaring tool.

[frostie_122]

It looks to already be 3/8 line. Is it not? 5/16 line on the vapor line? Which I would use for the return.

[71RestoRod]

Guess I was thinking it was all 5/16... or confusing my cars.