QJet Question...again! - Team Camaro Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools Display Modes
post #1 of 3 (permalink) Old Aug 18th, 03, 06:01 AM Thread Starter
Senior Tech
Paul
 
Join Date: Sep 2001
Location: Queen Creek AZ
Posts: 3,677
Post

I rebuilt a QJet and have been messing with the mixtures using my narrow band O2 sensor. I have some questions....

At idle I can adjust the idle screws to get it to stay in the .30 - .50 range. The engine runs OK idling in park, but while driving with accessories it runs kind of crappy set that lean. Using the old school method using a vacuum gauge/tach it seems to idle best on the rich side. Does that sound right?

I have a holley 110 GPH fuel pump and a pressure regulator. I have the pressure set to 6 PSI, anything higher than that tend to overrun the needle/seat. Is 6 PSI still too high?

From a stop on a flat road, at idle it's running on the rich side. I gently press the pedal(to avoid the accelerator pump shot) and the mixture goes lean and stays lean(no surging though, engine seems to be running fine) until I hit cruise speed and back the pedal off. While staying at a constant speed on a flat road the mixture again goes rich. I have tried different rods/jets and it always seems to go rich at cruise. I'm wondering if it could be pulling fuel in from somewhere at cruise when the vacuum is high. I set the float a 5/16 and when I pull the carb off the fuel level looks fine.

I just can't see anyway that the cruise mixture could go rich unless fuel is coming in from somewhere else. If the metering area was too big i t would be rich, but I have tried very small combos like 67 jets/46 rods with the same result.

I have no experience with QJets when they were in original like new working condition, so I have no baseline to compare to. I have only rebuilt the old "sat in the parts pile for years" type carbs, so it is feasable that the cores that I have been rebuilding could have problems.

Best of 1.55 - [email protected]
paulm is offline  
Sponsored Links
Advertisement
 
post #2 of 3 (permalink) Old Aug 20th, 03, 06:14 PM
Senior Tech
Steven
 
Join Date: Jan 2001
Location: Raleigh, NC
Posts: 1,046
Post

Don't overlook the choke ... I bet it is out of adjustment and not working properly ...
sdtsdt is offline  
post #3 of 3 (permalink) Old Aug 20th, 03, 07:33 PM
Moderator
David Pozzi
 
davidpozzi's Avatar
 
Join Date: Nov 1999
Location: Central California, USA
Posts: 10,094
Post

There is an adjustable stop for the metering rods. Early carbs had a screw coming in from the front, later carbs had an aluminum plug right over the adjuster. You can pop the plug out and tap it for a small pipe plug with allen head, remove the plug and turn the screw.
You would have to make a device to turn the screw with out of tubing squashed a bit to fit the screw.
David

Check my web page for First Gen Camaro suspension info:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

67 RS 327 original owner. 1965 Lola T-70
davidpozzi is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech 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.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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