Gas Tank Venting - Help - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 01-29-2007, 10:13 AM
72NOVA454
 
Last photo:
Join Date: Nov 2004
Location: chicago area
Age: 51
Posts: 922
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Gas Tank Venting - Help

Guys

I'm redoing the fuel lines from the rear mounted gas tank to the engine mounted fuel pump on my 72 chevy and I have a question.

I cut out and removed all the emission and vapor canister lines that connected to the fuel tank because I didn't want them in the way and they were probably trashed and rusted through anyway.

My question is - Is the fuel tank supposed to be vented to atmosphere somehow? (probably through some emission device right?) If the fuel filler cap is air tight, which it is, and the fuel line will be sealed up as long as the floats in the carb are at level, where does the pressure go inside the tank when the temperatures rise and the air expands. Is there supposed to be a pressure relief strategy or what?

I will begin the fuel line portion of my upgrades next weekend and want to plan ahead. I need your help.

Please explain.

Lee

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 01-29-2007, 10:23 AM
MI2600's Avatar
Member# 3287
 

Last journal entry: Vortec Heads
Last photo:
Join Date: Jul 2002
Location: N. Muskegon, MI
Posts: 2,632
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
My '72 El Camino has a very convoluted system. The previous owner(s) chopped it up for some sort of racing application, but I was able to restore most of it. I don't know if your '72 is the same, but the charcoal cannister is/was part of the venting system. I would suggest at least a vented cap, provided gas doesn't slosh out when full if the filler neck is in the rear.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 01-29-2007, 12:08 PM
xntrik's Avatar
Save a horse, Ride a Cowboy.
 
Last photo:
Join Date: Jul 2005
Location: Arkansas
Posts: 5,131
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
K I S S

Instead of a vented cap allowing vapors into the atmosphere, the tank had a line to a charcoal canister which collected those vapors. Upon startup, a solenoid opened allowing the engine to suck in the vapors from the canister. The solenoid venting system allows proper pressure balance inside the tank.

Old cars, especially those with the filler neck behind the license plate, had a line running higher than the tank under the body for venting rather than a vented cap which would have allowed fuel spillage during rapid acceleration.

You should consider using the original tank vent line to an elevated vent filter. You can use a common inline fuel filter on the end of the vent line to prevent injestion of dirt, etc. into the fuel tank. Point the open end down for water protection.

On a hot day you will smell gas vapors around your car.

Last edited by xntrik; 01-29-2007 at 12:24 PM.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 01-29-2007, 08:25 PM
Member
 
Last wiki edit: Vacuum brake bleeder set up
Join Date: Nov 2003
Location: So Cal
Posts: 1,245
Wiki Edits: 8

Thanks: 0
Thanked 0 Times in 0 Posts
I vote for getting another carbon canister and hiding it under the truck somewhere (not like you don't have the room under there). Other then the obvious fuel economy/emissions reasons the carbon canister is the vent for the gas tank as you discovered. If you are going to do without it be sure to install a roll-over check valve in the vent line. Otherwise if you ever (God forbid) get the thing on it's lid you have a much higher chance of going up in flames. 70's trucks had so little safety equipment as it was...don't go ditching the few that it did actually have Because I am cheap...a carbon canister will most likely be less money then a roll-over valve.

http://store.summitracing.com/partde...5&autoview=sku
http://store.summitracing.com/partde...5&autoview=sku

Roll-over (or tip-over as Summit calls them) valves are made for racing and are therefore will need adapters which can be $$$ in themselves.

Last edited by Triaged; 01-29-2007 at 08:31 PM.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
POR-15 gas tank resto kit cruzinTLT Body - Exterior 1 06-06-2006 05:08 PM
Gas Tank 1970 Chevy Camero kan Engine 0 05-21-2006 11:57 AM
32 'Tanks' gas tank - fuel surge/starvation? Limey Simon Engine 2 07-30-2004 01:18 PM
gas tank pressuring up montea General Rodding Tech 3 06-04-2004 08:37 PM
original 1936 ford gas tank fitting bomo General Rodding Tech 5 12-04-2003 04:20 PM


All times are GMT -6. The time now is 06:32 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.