Fouling plugs - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old 02-28-2017, 09:30 AM Thread Starter
 
SSnakeAce's Avatar
 
Join Date: Sep 2014
Location: Greenville, SC
Posts: 30
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Garage
Fouling plugs

Hi guys,

I'm just wrapping up swapping my GTO back to a 400 from the Chevy 350 it had when I bought it.

Spec wise, it's a '67 400 block with 11 bolt water pump, '68 intake, and '68 #16 heads, with what I believe to be an 041 cam, or at least something very similar. The current carburetor is a new Jet Performance quadrajet, #32102 , which I've made absolutely no adjustments to.

The motor starts up great, will idle fine, and runs good through the rpm range while parked - haven't been able to get it out on the road to test it under load because I can't get it to run long enough to try it. If I let it sit and idle for a bit, then cut it off, it won't crank again - it tries, but sputters and coughs for a few seconds until it dies.

Pulling the plugs shows that they're very black, so that says to me it's running rich. The other thing I noticed this weekend is that it started pushing fuel out the top of the carburetor, even after it died, around the accelerator pump. What would be the cause of this?

I feel like I can rule out the fuel pump, as I don't have the same behavior with the quadrajet from the Chevy, or a quadrajet from a Firebird Sprint that I had lying around. Would you agree? In those cases, the Chevy still runs rich, but that was true of it on the Chevy as well, and it doesn't foul the plugs like this Jet carb is doing. The Sprint quadrajet seems to not deliver enough fuel, which is probably true given that it was for a 6 cylinder.
SSnakeAce is offline  
Sponsored Links
Advertisement
 
post #2 of 6 (permalink) Old 02-28-2017, 10:16 AM
 
1968gto421's Avatar
 
Join Date: Mar 2014
Location: Travelers Rest, South Carolina
Posts: 752
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 70 Post(s)
Have you pulled the air horn and checked the float level? If your fuel pump does not have excessive pressure than the float level could very well be off or the needle/seat assembly has dirt in it preventing full closure.

Hope this helps. If not, keep asking us, someone will have a better idea.
1968gto421 is offline  
post #3 of 6 (permalink) Old 02-28-2017, 04:04 PM
 
64GTOConvertible's Avatar
 
Join Date: Aug 2016
Location: NE PA
Posts: 193
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Yah, sounds like a stuck float making the mix very rich. You may also need to adjust that carb. What kind of fuel pump are you running? Do you also run a pressure regulator?
64GTOConvertible is offline  
 
post #4 of 6 (permalink) Old 02-28-2017, 07:03 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,451
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 347 Post(s)
Garage
Pushing fuel out the carb top can indicate a couple things. Seeing it is "new", I would first call the supplier and let them know what is happening. They may have a warranty and if you pull off the top, you may void the warranty or return policy if they ask you to send it back for a replacement.

Float level could be set to high. The needle and seat could be stuck open or a piece of debris got under the needle not allowing it to seat completely and shut off the fuel flow if the float is indeed set correctly. Your fuel pump pressure could be too high. You did not say what type of fuel pump you are using. There are some aftermarket pumps designed to have higher pressures which will work better with a Holley which recommends between 5-7 pounds with 7 pounds at idle - too high for the Q-jet. You want nearer to 4 lbs fuel pressure with a Q-jet. Q-jet's want fuel volume, not fuel pressure.

So a few things you can check.
PontiacJim is offline  
post #5 of 6 (permalink) Old 04-24-2017, 10:44 AM Thread Starter
 
SSnakeAce's Avatar
 
Join Date: Sep 2014
Location: Greenville, SC
Posts: 30
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Garage
Just to provide some closure on this for anyone searching later - I ended up sending back the Jet carb. They took it as a warranty return, and so I while I assume that you guys were right that it was a float level issue, I didn't want to open up the carb for fear of voiding the warranty.

The replacement carb has been much better.
SSnakeAce is offline  
post #6 of 6 (permalink) Old 04-24-2017, 02:32 PM
 
1968gto421's Avatar
 
Join Date: Mar 2014
Location: Travelers Rest, South Carolina
Posts: 752
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 70 Post(s)
Hope Jet does you right this time. If not, you may want to try Cliff Ruggles, THE Q-jet guru. He has written THE book on Q-jet carbs with rebuild and performance mods in it. Having the book as reference is a must for us Q-jet guys. Here is a link:

Cliffs High Performance Quadrajets :: Qjet Carburetor Rebuilding Book

Cliff will also rebuild your carb with any needed mods or sell you one outright. He has a backlog so bear with him. Another Q-jet source that has many high recommendations is Sean Murphy. Here is his link:

https://www.smicarburetor.com/products/sfID1/28/sfID2/9

On the PY forum. a member there (64speed) is from Westminster over in Oconee county and had 3 Jet Rochester carbs before sending them all back and doing a Holley from Summit. Hopefully you will have better luck.
1968gto421 is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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
Plugs bnreed3 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance 0 04-20-2016 09:03 AM
TR 55 Plugs rtsoul Service, Maintenance and Technical Discussion 5 12-13-2012 10:05 PM
New Plugs SIXT5GTO 1964-1974 Tempest, Lemans & GTO General Discussion 2 03-17-2011 10:11 PM
pulse plugs/pulsestar plugs htowngto04 Service, Maintenance and Technical Discussion 7 02-21-2009 03:14 AM
Plugs TxSoldier6.0 Service, Maintenance and Technical Discussion 8 11-08-2008 03:19 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