Carburetor leak down - Pontiac GTO Forum
User Tag List

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 11 (permalink) Old 03-21-2012, 02:52 PM Thread Starter
 
Join Date: Mar 2012
Location: Texas
Posts: 56
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Carburetor leak down

Hi everyone. I've almost completely restored my grandfather's 65 Tempest. Everything has gone smoothly save this one frustration.

I have rebuilt the carb- it runs beautifully, however if I don't drive it within a week, the carb is dry. I can't locate the source of the leak. Any ideas? Thanks.


Sent from my Autoguide iPhone app

1965 Pontiac Tempest Custom - 326 bone stock
RT-1 is online now  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 03-21-2012, 02:54 PM Thread Starter
 
Join Date: Mar 2012
Location: Texas
Posts: 56
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
I should add- its the stock Rochester 2 barrel on a 326


Sent from my Autoguide iPhone app

1965 Pontiac Tempest Custom - 326 bone stock
RT-1 is online now  
post #3 of 11 (permalink) Old 03-21-2012, 06:13 PM
64-67 Expert
 
geeteeohguy's Avatar
 
Join Date: Feb 2008
Location: Fresno, California
Posts: 8,543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 118 Post(s)
On the 2bbl carb, bowl leakage is not the norm. My bet is that the newer, highly volatile gasoline is simply evaporating. 3 solutions: drive it more often; install an electric fuel pump to prime it; or simply crank it over in 15 second intervals with a rest period in between to let the starter cool until it cranks up. It shouldn't take long for fuel to get to the carb, and you'll always have oil pressure on the cold start...not a bad thing.
geeteeohguy is offline  
 
post #4 of 11 (permalink) Old 03-21-2012, 07:27 PM
 
lars's Avatar
 
Join Date: Sep 2004
Posts: 445
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 1 Post(s)
Although your Rochester 2-Jet is significantly different from a Q-Jet, my Q-Jet Tuning paper has a complete section on fuel bleed-down/hard start issues that apply to your 2-barrel in many cases - it also addresses the issue outlined by geeteeohguy above. Simply e-mail me for a copy of the paper and check out the last section of the paper on this issue.

Lars
[email protected]
lars is offline  
post #5 of 11 (permalink) Old 03-21-2012, 09:57 PM Thread Starter
 
Join Date: Mar 2012
Location: Texas
Posts: 56
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
I've been fighting this for a couple of years. I did put an inline electric fuel pump which does overcome the issue. I was worried if fuel was leaking internally, I'd be draining several ounces into the cylinders which would cause fuel dilution of the oil. I've read about the higher evaporation rates of newer fuels, but I don't have this problem on my 57 Chevy.

On a side note - why on earth in this era of emission requirements would they make formulations that evaporate more rapidly than the old blends???

1965 Pontiac Tempest Custom - 326 bone stock
RT-1 is online now  
post #6 of 11 (permalink) Old 03-21-2012, 10:19 PM
 
lars's Avatar
 
Join Date: Sep 2004
Posts: 445
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by RT-1 View Post
Why on earth in this era of emission requirements would they make formulations that evaporate more rapidly than the old blends???
Do you honestly believe that your elected political (left wing) officials are technical engineering experts on the issues of emissions...? Repeat after me, "Corn Grower's Lobbyists," "Alternative Fuels."

If you really think these people have "emissions" in mind, please sell me your Tempest for $500. This is about making money.

Lars
lars is offline  
post #7 of 11 (permalink) Old 04-02-2012, 06:46 PM Thread Starter
 
Join Date: Mar 2012
Location: Texas
Posts: 56
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Ok- I read Lars excellent article. I ordered a new power valve since that's the only thing on the bottom of the fuel bowl. I also ordered a fuel pump rebuild kit. Hopefully if I do all these things it will stop the leak down.


Sent from my Autoguide iPhone app

1965 Pontiac Tempest Custom - 326 bone stock
RT-1 is online now  
post #8 of 11 (permalink) Old 04-03-2012, 12:40 PM
 
lars's Avatar
 
Join Date: Sep 2004
Posts: 445
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 1 Post(s)
Not likely. The power valve cannot leak the fuel out of the bowl, and the 2GC carb has the needle/seat on the top of the carb, so fuel pump drainback is not an issue. You are suffering from the fuel issue discussed earlier, and the fuel is simply evaporating below the level of the accel pump supply slot. You either live with it, or start the engine more frequently. You can also use an electric pump as suggested above. Verify that your accel pump is, in fact, operating and functional (strong solid squirt when the carb bowl is full). If it is, you have little recourse on this issue.

There is a remote possibility that you could have a cracked or porous carb casting. To verify, you can pull the carb, fill the bowl, and set the carb up on your workbench on top of some tall sockets at the throttle plate bolt holes: Observe the bottom of the carb for leaks or drips. If nothing is dripping out the bottom, your only problem is the evaporation issue.

Lars
lars is offline  
post #9 of 11 (permalink) Old 04-04-2012, 07:11 PM
 
jmt455's Avatar
 
Join Date: Mar 2012
Location: SE Michigan
Posts: 725
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Are you using the inline (paper) fuel filter in the carb inlet? That filter has a check valve built into its inlet end. If it's not there or it is damaged, fuel could (possibly) be draining back out of the carb after the pump pressure drops.

1968 Pontiac GTO
1983 Pontiac Bonneville (G) wagon
2008 Pontiac G8 base
jmt455 is offline  
post #10 of 11 (permalink) Old 04-05-2012, 07:57 AM
 
allpawl66's Avatar
 
Join Date: May 2008
Location: PA.
Posts: 391
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
When done driving , manually close the choke flap as it will slow the evaporation of the alcohol based fuel .
allpawl66 is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
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:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Which Carburetor?? wvmtnman 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion 1 02-12-2012 09:39 AM
Carburetor Rebuild NEEDLEZ 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion 1 09-30-2011 06:16 PM
Carburetor PisnNapalm 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion 62 01-04-2011 11:38 AM
What Carburetor? kjk990 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion 11 09-02-2010 09:55 PM
Carburetor help....please PontiacDave 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion 4 11-12-2009 10:57 PM

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

 
For the best viewing experience please update your browser to Google Chrome