Carb Problems - Pontiac GTO Forum
Pontiac GTO Pontiac GTO Forum

» Auto Insurance
Wheel & Tire Center

Go Back   Pontiac GTO Forum > The 1964-1974 Pontiac GTO > 1964-1974 Tempest, LeMans & GTO Technical Discussions
Register Home Forum Active Topics Photo Gallery Garage Search Today's Posts Mark Forums Read Auto EscrowInsurance

GtoForum.com is the premier Pontiac GTO Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
Old 12-31-2012, 02:19 PM   #1 (permalink)
 
Join Date: Oct 2009
Posts: 10
My Photos: (0)
Carb Problems

I am having trouble with my car when i put it to full throttle. I have a Edelbrock 650 carb on my gto and as long as its in Park or Neutral i can open it up and have no problems, but when i get on the highway and put the hammer down it tries to die out on me. Is there anyone out there that might have any idea of what the problem may be.
revOlg1206 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 12-31-2012, 04:21 PM   #2 (permalink)
64-67 Expert
 
geeteeohguy's Avatar
 
Join Date: Feb 2008
Location: Fresno, California
Posts: 6,980
My Photos: (2)
You're starving for fuel. Could be delivery, could be carb. For a GTO, a 650 is marginal....the stock Q-jet is 750cfm for the 400 and 800 cfm for the 455. You can check fuel pump pressure and volume, and if ok, it's the carb. If not, it's the pump or a restriction in the lines.
geeteeohguy is offline   Reply With Quote
Old 12-31-2012, 04:32 PM   #3 (permalink)
 
Join Date: Oct 2009
Posts: 10
My Photos: (0)
ok i'll check all of those ..one question how can i check the fuel pump to see if im getting good enough pressure.....i have a filter on the inlet line before the line goes into the carb, could that be part of the problem.
revOlg1206 is offline   Reply With Quote
Old 01-01-2013, 04:07 AM   #4 (permalink)
 
Join Date: Oct 2012
Location: Texas
Posts: 555
My Photos: (7)
carb

Just recently went through this with our '66 Lemans convertible with a Carter 625 cfm competition carb. Yes, it would be extra nice to have a period correct intake and carb. such as a Qjet or Holley, but don't forget that Carter was also listed as an option in the '66 chassis shop manual. Carter= Edelbrock in this day and age. Don't know what year Goat you got, but I ran that 625 on the old 326. Now it is on a '71 455. VERY small carb. for that engine; didn't ever think that would run the 455, but lo and behold... she run damn good now... Had a terrible time with it, checked everything under the sun: timing, dist., wiring, carb. rebuild-(three times) etc... turned out to be a cheesy Chinese crafted brass vacuum block at the back of carb.(attached to power brakes and modulator) that had a casting flaw and was sucking just enough air to make it run slightly higher rpms at idle and do all sorts of crazy things. One day it'd run great, next day terrible. Problem didn't show up with any amount of carb. cleaner spray. Had to disassemble that vacuum block and THOROUGHLY visually inspect it. Check basics first... VACUUM LEAKS, carb. gasket, ignition timing, fuel filter, vacuum port configuration, fuel pump pressure, float level, compression check, etc... You'll get to the bottom of it with a little persistence. You can rent a fuel pump pressure tester at most any auto parts store. Maybe someday I'll have a real intake and carb. on mine, but for now, this'll do.
gjones is offline   Reply With Quote
Old 01-01-2013, 11:15 AM   #5 (permalink)
Super Moderator
 
BearGFR's Avatar
 
Join Date: Aug 2008
Location: Springtown, TX
Posts: 4,472
My Photos: (12)
Garage
When you say "it tries to die out", what exactly does it do? Does it stumble, and sputter? Does it behave like someone just turned off the key briefly? What?

Most of all, you need a systematic approach. Check for and eliminate one thing at a time - you'll eventually find it. Engines behave quite differently under load in actual driving conditions than they do in neutral with no load on them, so the fact that it seems ok sitting in your driveway really tells you very little. Start with the easy things first. If any/all of the fuel filters aren't new, replace them. Check your ignition timing, both at idle and at 2500 rpm if possible (doing that requires a timing light that can read "total" advance). Carefully check for any vacuum leaks anywhere around the carb, fittings, hoses, and intake manifold.

with GeeTee that the carb you have is a little small for the engine, but that shouldn't make it stumble or act like it's going to die as long as it's set up properly.

The only reliable way to check fuel pressure is to use a good fuel pressure gauge. It needs to be installed in the line close to the carb inlet, and if you want to see what's happening under driving conditions, temporarily mounted OUTSIDE THE CAR so you can see it while driving. Don't "cheap out" and put the gauge inside the car with you - one problem with a fuel line leak and you'll be spraying gasoline all over the inside of the car and maybe all over yourself - not something you want to take a chance with.

Bear
__________________
BearGFR
Garland, TEXAS
BearGFR is offline   Reply With Quote
Old 01-01-2013, 09:30 PM   #6 (permalink)
 
SDGoat619's Avatar
 
Join Date: Mar 2011
Posts: 107
My Photos: (0)
I had the same issue with the 800cfm e-brock on my 455. I chased the problem all over the car. New fuel pump and line, new coil for the dizzy, new wires and plugs, new jets and rods. While everything helped a little my real issue was that the needle and seats that allow the fuel to fill the floats were caked with grime and the fuel couldnt get into the carb fast enough to keep the car going while in drive. In park and the 455 would rev and was very responsive to the throttle. these cars need very little fuel in park to keep running. In closing after 300 bucks in new parts were I should have started was by opening up the carb and running through it with my air compressor and two cans of carb cleaner.
__________________
65 LeMans, 455,TH400, Edelbrock preformer Intake&Carb, K&N Filter, Custom Headers & Dual Exhaust W/ H pipe, 15in ralley wheels...... More to come.
SDGoat619 is offline   Reply With Quote
Old 01-02-2013, 01:09 AM   #7 (permalink)
 
Join Date: Oct 2012
Location: Texas
Posts: 555
My Photos: (7)
carb

You bet! It appears the needles and seats in these E-brock's and newer style Carters are very touchy. But the major problems seem to be in the accelerator pump delivery passages. Make certain that you're getting a good solid spray of fuel out of the discharge nozzles. Like I said, I disassembled the carburetor 3 times and checked float levels (and tweaking them), cleaned it, blew it out, scrutinized all settings, and STILL had problems. Was just about ready to give up and buy a Qjet, but found that vacuum leak at the final hour. Don't overlook the obvious, even though it may not seem all that obvious.
gjones is offline   Reply With Quote
Old 01-08-2013, 05:42 PM   #8 (permalink)
 
Join Date: Oct 2009
Posts: 10
My Photos: (0)
Thanks everyone for your input ....im going to try to go through everything and see if i can get this thing figured out.
revOlg1206 is offline   Reply With Quote
Old 01-09-2013, 12:15 PM   #9 (permalink)
64-67 Expert
 
geeteeohguy's Avatar
 
Join Date: Feb 2008
Location: Fresno, California
Posts: 6,980
My Photos: (2)
Fuel pressure gauges are available at the parts store. Not super cheap. The volume test is in the manual, usually. It's a cranking test and a fire hazard, so be careful. It involves disconnecting the fuel line and cranking the engine over with the ign disabled...if you fill up a quart jar with fuel in about 20 seconds you're okay. Usually NOT the problem. Check your pressure, your lines (especially the rubber line back by the tank!!) etc. Any cracking of the rubber, replace the lines.
geeteeohguy is offline   Reply With Quote
Old 01-09-2013, 08:10 PM   #10 (permalink)
 
chuckha62's Avatar
 
Join Date: Apr 2010
Location: NorCal
Posts: 535
My Photos: (0)
Your carburetor is certainly on the small side for your application, but I tend to go with Bear on this one... by properly setting up your initial timing and your advance mechanism(s) you should be able to eliminate much of your drivability issues.

There's an old saying that goes "90% of carburetor problems are actually ignition timing." Been there, done that.
__________________
Don't judge a man until you've walked a mile in his shoes. That way, you'll be a mile away AND you'll have his shoes!
chuckha62 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac GTO > 1964-1974 Tempest, LeMans & GTO Technical Discussions


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

Posting Rules
You may not post new threads
You may not 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
Cold start problems with rochester quadrajet. Fuel draining out of carb ? dillon14 1964-1974 GTO General Discussion 8 07-15-2011 11:55 PM
Carb Adjustment Problems RiMZCoat 1964-1974 Tempest, LeMans & GTO Technical Discussions 4 03-12-2010 08:48 AM
65 carb problems sdrake 1964-1974 Tempest, LeMans & GTO Technical Discussions 8 01-10-2010 09:31 PM
Carb Help GTO'n'TRANSAM 1964-1974 Tempest, LeMans & GTO Technical Discussions 8 11-26-2008 10:01 AM
carb in a 69' GTO Luiz 1964-1974 Tempest, LeMans & GTO Technical Discussions 2 12-27-2007 11:18 PM

Powered by vBadvanced CMPS v3.2.2

All times are GMT -5. The time now is 10:38 AM.



Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.3.2
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.